ENI - Directional Control & Surveying Procedures

ARPOENI S.p.A.Agip Division

ORGANISINGDEPARTMENT

TYPE OFACTIVITY'

ISSUINGDEPT.

DOC.TYPE

REFER TOSECTION N.

PAGE. 1OF 67

STAP P 1 M 6120

The present document is CONFIDENTIAL and it is property of AGIP It shall not be shown to third parties nor shall it be used forreasons different from those owing to which it was given

TITLEDIRECTIONAL CONTROL & SURVEYING PROCEDURES

DISTRIBUTION LIST

Eni - Agip Division Italian DistrictsEni - Agip Division Affiliated CompaniesEni - Agip Division Headquarter Drilling & Completion UnitsSTAP ArchiveEni - Agip Division Headquarter Subsurface Geology UnitsEni - Agip Division Headquarter Reservoir UnitsEni - Agip Division Headquarter Coordination Units for Italian ActivitiesEni - Agip Division Headquarter Coordination Units for Foreign Activities

NOTE: The present document is available in Eni Agip Intranet (http://wwwarpo.in.agip.it) and aCD-Rom version can also be distributed (requests will be addressed to STAP Dept. inEni - Agip Division Headquarter)

Date of issue:

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� Issued by P. MagariniE. Monaci C. Lanzetta A. Galletta28/06/99 28/06/99 28/06/99

REVISIONS PREP'D CHK'D APPR'D

28/06/99


IDENTIFICATION CODE PAGE 2 OF 67

REVISIONSTAP-P-1-M-6120 0

INDEX

1. INTRODUCTION 51.1. PURPOSE OF THE MANUAL 51.2. IMPLEMENTATION 51.3. UPDATING, AMENDMENT, CONTROL & DEROGATION 5

2. GENERAL RESPONSIBILITIES 62.1. COMMUNICATION STRUCTURE 62.2. PERSONNEL RESPONSIBILITIES 6

2.2.1. Drilling & Completion Manager 62.2.2. Drilling Superintendent 62.2.3. Senior Drilling Engineer 72.2.4. Drilling and Completion Supervisor (Rig-Site) 82.2.5. Contractor Directional Supervisor 92.2.6. Contractor Directional Operator (Rig-Site) 102.2.7. Contractor Surveying Operator (Rig-Site) 11

2.3. CONTRACTOR COMPETENCE ASSURANCE 11

3. WELL PLANNING PROCEDURE 123.1. OBJECTIVES 123.2. DEFINITIONS 12

3.2.1. Vertical Well 123.2.2. Deviated Well 123.2.3. Rotary Kelly Bushing (RKB) 123.2.4. Origin Reference Point (ORP) 133.2.5. Projected Well Plot 133.2.6. Directional Well Programme 13

3.3. PLANNING RESPONSIBILITIES 133.4. PLANNING REQUIREMENTS 14

3.4.1. Software Capabilities 143.4.2. Decision Process 153.4.3. Origin Reference Points (for well planning) 15

3.5. PRELIMINARY DIRECTIONAL PLAN INFORMATION 163.6. IMPACT OF THE RADIOUS OF UNCERTAIN (ROU) 163.7. PROJECTED DIRECTIONAL PLAN INFORMATION 173.8. PROJECTED WELL PLOTS 18

3.8.1. Well Plan 183.8.2. Spider Plot 193.8.3. Proximity Evaluation 19

3.9. DIRECTIONAL WELL PROGRAMME 193.10. PRE-SPUD MEETING 213.11. TECHNICAL MEETINGS 21




4. SURVEYING POLICY 224.1. OBJECTIVES 224.2. DEFINITIONS 22

4.2.1. Definitive Survey 224.2.2. Origin Reference Point (ORP) 224.2.3. Reference North 224.2.4. Tie-In Point (TIP) 234.2.5. Foresight Reference (FR) 234.2.6. Dogleg Severity (DLS) 234.2.7. Magnetic Declination 234.2.8. Uncertainty Factor (UF) 234.2.9. Magnetic Survey Tool List 234.2.10. Gyroscopic Survey Tool List 23

4.3. SURVEYING RESPONSIBILITIES 254.4. SURVEYING REQUIREMENTS 26

4.4.1. Approved Surveying Tools 264.4.2. Software Capabilities 264.4.3. Survey Calculation Method 264.4.4. Survey Tool Uncertainty 264.4.5. Minimum Surveying Programme 264.4.6. Accuracy Comparison Methods 274.4.7. Azimuth Reference 274.4.8. Tie-In Points 274.4.9. Measurement System 274.4.10. Horizontal Uncertainty Factors 274.4.11. Vertical Uncertainty Factors 274.4.12. Magnetic Declination 284.4.13. Rigsite Directional Data Requirement 28

4.5. CONSIDERATIONS FOR SURVEY TOOL SELECTION 294.5.1. Directional Drilling Control 294.5.2. Well profile Verification 304.5.3. Orientation Surveys 32

4.6. QUALITY CONTROL (QC) 344.6.1. Magnetic Survey Tools (at Rig-site) 344.6.2. Gyroscopic Survey Tools (at Rig-site) 354.6.3. Schlumberger ‘Guidance Continuous Tool 364.6.4. Ferranti Inertial Survey Tool 364.6.5. In-House Quality Control 36

4.7. SURVEY PROGRAMME FOR VERTICAL HOLES 374.8. SURVEY PROGRAMME FOR DEVIATED HOLES 37

5. ANTI-COLLISION PROCEDURE 405.1. OBJECTIVES 405.2. DEFINITIONS 40

5.2.1. Ellipsoid of Uncertainty 405.2.2. Radius of Uncertainty (ROU) 405.2.3. Dogleg Potential (DLP) and Dogleg Severity (DLS) 405.2.4. Horizontal Uncertainty Factor (UF) 415.2.5. Current Well (CW) 415.2.6. Target Well (TW) 415.2.7. Separation Distance (SD) 415.2.8. Centre to Centre Distance (CCD) 41




5.2.9. Separation Ratio (SR) 415.3. ANTI-COLLISION REQUIREMENTS 45

5.3.1. Software Capabilities 455.3.2. Projection Technique (with Rotary Assemblies) 455.3.3. Projection Technique (with Steerable Assemblies) 455.3.4. Worst Case Projection Technique 45

5.4. CONSIDERATIONS IN PLANNING A NEW MULTI-WELL SITE 475.5. ANTI-COLLISION RESPONSIBILITIES 48

5.5.1. Planning Wells (with interference between existing producing/completed wells and newwells) 48

5.5.2. Planning Wells (with interference between existing, non completed/P&A wells and newwells) 49

5.6. PLUGGING OF COMPLETED TARGET WELLS (when separation is in zone x) 505.7. SUSPENSION OF CURRENT WELL (when separation is in zone y or in zone z) 505.8. WELL-SITE PROCEDURES 515.9. EXAMPLE PROXIMITY CALCULATION 55

6. RECORD KEEPING 576.1. OBJECTIVES 576.2. DEFINITIONS 57

6.2.1. Working Surveys 576.2.2. Definitive Surveys 576.2.3. Final Report 57

6.3. REPORTING RESPONSIBILITIES 576.4. SURVEY REPORTING FORMAT 586.5. DIRECTIONAL CONTRACTOR’S FINAL REPORT 59

6.5.1. Title Page 596.6. SUMMARY OF OPERATION/SURVEY PROGRAMME 59

6.6.1. BHA Performance Report 596.6.2. Definitive Survey Listing 596.6.3. Summary Plot 606.6.4. Directional Drilling Analysis 60

7. DIRECTIONAL DRILLING/SURVEYING SERVICES PROCUREMENT 617.1. PROCURING SERVICES & MATERIALS PROCEDURES 617.2. CONTRACTOR EVALUATION 62

7.2.1. ARPO FB-1 Malfunction & Failure Report 627.2.2. ARPO FB-2 Contractor Evaluation Form 62




1. INTRODUCTION1.1. PURPOSE OF THE MANUAL

The purpose of the Directional Drilling and Surveying Manual is to guide technicians andengineers, involved in Eni-Agip’s Drilling & Completion worldwide activities, through theProcedures and the Technical Specifications for Directional Drilling and Surveyingoperations which are part of the Corporate Standards.Such Corporate Standards define the requirements, methodologies and rules that enable tooperate uniformly and in compliance with the Corporate Company Principles. This, however,still enables each individual Affiliated Company the capability to operate according to locallaws or particular environmental situations.The final aim is to improve performance and efficiency in terms of safety, quality and costs,while providing all personnel involved in Directional Drilling & Surveying activities withcommon guidelines in all areas worldwide where Eni-Agip operates.It is intended to guide users towards using procedures which have been found to providethe most efficient and cost effective operations.

1.2. IMPLEMENTATIONThe policies specified herein will be applicable to all of Eni-Agip Division and Affiliatesoperations world-wide.All supervisory and technical personnel engaged in Eni-Agip Division and Affiliatesdirectional control and surveying operations are expected to make themselves familiar withthe contents of this manual and be responsible for compliance to it’s policies andprocedures.

1.3. UPDATING, AMENDMENT, CONTROL & DEROGATIONThis is a ‘live’ controlled document and, as such, it will only be amended and improved bythe Corporate Company, in accordance with the development of Eni-Agip Division andAffiliates operational experience. Accordingly, it will be the responsibility of everyoneconcerned in the use and application of this manual to review the policies and relatedprocedures on an ongoing basis.Locally dictated derogations from the manual shall be approved solely in writing by theManager of the local Drilling and Completion Department (D&C Dept.) after theDistrict/Affiliate Manager and the Corporate Drilling & Completion Standards Department inEni-Agip Division Head Office have been advised in writing.The Corporate Drilling & Completion Standards Department will consider such approvedderogations for future amendments and improvements of the manual, when the updating ofthe document will be advisable.




2. GENERAL RESPONSIBILITIESThis section outlines the communication structure and general personnel responsibilitieswith regard to directional drilling and surveying operations. Operational specific individualpersonnel responsibilities are detailed in each relevant section of the manual.

2.1. COMMUNICATION STRUCTUREThe Eni-Agip Division and Affiliates communication structure will be in accordance with thelocal Drilling & Completion Department’s organisation and to meet with the necessaryreporting requirements of the Eni-Agip Division and Affiliates head office.

2.2. PERSONNEL RESPONSIBILITIESThe following sections describe the general responsibilities of personnel involved indirectional drilling and surveying.

2.2.1. Drilling & Completion ManagerThe Drilling & Completion Manager will have responsibility for:

• Enforcing technical specifications issued by ARPO/STAP in the tender request.• Project Well Plan approval. (Refer to Section 3.4.2)• Ensuring compliance with policy and development of local procedures in

accordance with company policies and local legislation.• Ensuring the maintenance of safe well operations when drilling in close proximity

to other wells. (Refer to Sections 5.5.1 and 5.5.2)• Ensuring reports, ARPO FB-01, ARPO FB-02 (for Directional Drilling and

Surveying services) forms. and survey calculation's output are forwarded to AgipHead Office. (Refer to Sections 6.4, 7.2.1 and 7.2.2)

2.2.2. Drilling SuperintendentThe Drilling Superintendent will have responsibility for:

• Ensuring the well progress follows the approved well directional plan.• Providing technical advice to drilling rig-site personnel on a daily basis as

required.• Liaising with the Directional Contractor onshore to ensure the proper personnel

and materials are supplied to the rig-site in scheduled time.• Conducting an evaluation of the Directional Contractor's performance for current

contracts and future tender evaluation. This evaluation contributes to thecompletion of forms ARPO FB-01 and ARPO FB-02. (Refer to sections 7.2.1and 7.2.2)




2.2.3. Senior Drilling EngineerThe Senior Drilling Engineer will have responsibility for:

• Ensuring the compilation, approval and issuing of the well programme to includethe Directional and Surveying plan. (Refer to Section 3.9)

• Ensuring full and consistent consideration of all related issues from both thetechnical and economic point of view. (Refer to Sections 3.3 , 5.5.1 and 5.5.2)

• Requesting, receiving, reviewing and approving for distribution, the Contractor’sProjected Well Plots.

• Liaising with the Directional Drilling Contractor to ensure effective execution ofthe approved Directional Programme.

• Providing technical answers to operational problems as they arise.• Responsible for producing contingent amendments to the Directional and

Surveying Programme (e.g. in case of a side track).• Reviewing techniques and procedures for future programmes.• Producing a Final Well Report including the directional and surveying section as

supplied by the Directional Contractor. (Refer to Section 6.3)• The supervising and managing of the ‘Definitive Survey Records’. (Refer to

Section 6.5)• Confirming the accuracy of data for the Final Well Plots and directional Well

Programmes.

Note SDE approval is required on all Final Well Plots and Well Programmes.(Refer to Section 3.3)

• Aiding the Drilling Superintendent evaluating the Directional Drilling Contractor'sperformance for current contracts and future tender evaluation.




2.2.4. Drilling and Completion Supervisor (Rig-Site)The Drilling Supervisor at the rig-site will have responsibility for:

• Making himself/herself thoroughly conversant with the well programme and thewell directional plan and ensuring the correct execution of the programme inaccordance to the directional targets. (Refer to Section 5.8)

• Ensuring that all the necessary equipment, materials and personnel required tocarry out directional operations are available on schedule and ensuring promptreturn of same after operations are complete.

• Organising pre-job meetings at the rig site to ensure that the service companiesand drilling contractor personnel understand the operations and tasks to beperformed and their individual responsibilities.

• Reviewing the progress of operations, regularly reporting to the DrillingSuperintendent and Senior Drilling Engineer, and offering suggestions forprogramme improvement and/or solutions to problems as they arise.

• Supervising and managing the directional drilling and surveying programme.• Aiding the Drilling Superintendent checking and assessing the competence of

service company personnel, their performance and equipment suitability andreporting this evaluation on ARPO FB-1 and ARPO FB-2 forms. (Refer toSections 6.4, 7.2.1 and 7.2.2)

• Reporting/conveying survey information to the base office in a timely fashion sothat field calculations can be checked ensuring that the appropriate form is filledin correctly, accurately and completely. (Refer to Section 6.3)

• Ensuring that all required procedures, to meet with the Eni-Agip Division andAffiliates anti-collision policy, are taken before drilling operations commence.(Refer to Section 5)

• Ensuring that appropriate actions are taken to shut-in wells or halt drillingoperations in adherence to the anti-collision policy. (Refer to Sections 5.5.1 and5.5.2)




2.2.5. Contractor Directional SupervisorNote The necessity of a Directional Contractor Supervisor will be evaluated each timedepending on the particular programme. This will be specified in the Directional DrillingServices Tender - technical specification section. Technical Supervisor will haveresponsibility for:

• Ensuring that the agreed and safe established working practices/proceduresbetween Eni-Agip Division and Affiliates and the Directional Contractor arefollowed by the rig-site Contractor Directional Operators.

• Being familiar with and working within the guidelines of the Eni-Agip Division andAffiliates Directional and Surveying Procedures as laid out in this manual.

• Ensuring reporting meets with the local communication structure.• Making himself/herself thoroughly familiar with the well plan and its

requirements.• Checking and confirming the accuracy of the well planning information as

received from the SDE.• Briefing the Contractor Directional Operator on the well plan and its

requirements prior to proceeding to the rig.• Ensuring that the equipment provided by the Directional Contractor to the rig-site

meets with programme requirements and liasing with the Eni-Agip Division andAffiliates representatives for future requirements.

• Consulting with local Eni-Agip Division and Affiliates personnel on a daily basiswhile the programme is being conducted.

• Confirming survey and proximity calculations on a daily basis, or more frequentlyas required.

• Checking and approving the Final Well Report, as detailed in Section 6.5, beforereleasing the copies to Eni-Agip Division and Affiliates.




2.2.6. Contractor Directional Operator (Rig-Site)The Contractor Directional Operator will have responsibility for:

• Adhering to the agreed and established safe working practices between Eni-Agip Division and Affiliates and the Directional Contractor.

• Making himself familiar with and working within the Eni-Agip Division andAffiliates Directional and Surveying Procedures as laid out in this manual.

• Reporting according to the communication structure .• Providing immediate reports of any accidents/major operational incidents and

near-misses relating to the programme.• Making himself thoroughly familiar with the well plan and requirements.• Checking the accuracy and completeness of the Project Well Plot and Well

Programme, as approved by the SDE, before the directional drilling commences.• Ensuring that the rig-site equipment inventory meets programme requirements

and consulting with the Drilling and Completion Supervisor to cover future needsin ahead of time.

• Providing the standard daily reports comprising a summary of drilling activity, thedrilling assembly in use, drilling parameters, survey data, equipmentrequirements, proposed BHA's and operational suggestions.

• Maintaining up to date survey calculations and projections to keep within thewell specified tolerances as outlined in the Well Programme.

• Maintaining up to date proximity calculations and projections and taking actionsto keep the well path within specified tolerances as outlined in the WellProgramme.

• Ensuring that data relating to well proximity calculations is communicated to theDrilling Superintendent/SDE and to the Contractor Directional Supervisor (ifapplicable) as information becomes available. Enabling prompt back-upcalculations to confirm rig-site data.

• Providing BHA designs and ensuring they are suitable for survey programmerequirements and advising maintenance requirements.

• Supervising directional drilling operations.• Maintaining current records of drilling parameters and descriptions of each

assembly drilling the well.• Supervising tripping and reaming operations to maintain hole condition and to

prevent unintended side-tracks.• Preparing equipment lists for immediate return of rental equipment to the

Contract’s base.• Preparing a Final Well Report, as detailed in Section 6.5, when the drilling of the

well has been completed.• Monitoring dogleg severity and ensuring that corrective action is taken to keep

doglegs within specification.




2.2.7. Contractor Surveying Operator (Rig-Site)The Contractor Surveying Operator at the rig-site will have responsibility for:

• Adhering to the agreed and established safe working practices between Eni-Agip Division and Affiliates and the Survey Contractor.

• Being familiar with and working within the Eni-Agip Division and AffiliatesDirectional and Surveying Procedure as laid out in this manual.

• Adhering to the communication structure .• Providing immediate reports of any accidents or major operational incidents and

near misses relating to the programme.• Making himself thoroughly familiar with the programme surveying and

requirements.• Ensuring all data has been acquired from the Eni-Agip Division and Affiliates

office in order to make accurate survey calculations. (Refer to Section 4.4)• Ensuring that the rig-site survey equipment inventory meets programme

requirements and liasing with the Drilling Supervisor to cover futurerequirements according to schedule.

• Ensuring that the survey tool has been checked and calibrated as per the QCprocedures of the Surveying Contractor immediately before and after running inthe hole and providing relevant documentation. (Refer to Section 4.6)

• Providing daily reports of survey data (for on going measurements).• Providing field calculated survey results as soon as practical (for single shot

surveys).• Ensuring reported survey depths are accurate.• Confirming that magnetic survey tools are placed in the BHA as specified in

Section 4.6, so as to minimise interference.• Keeping complete records of equipment used during drilling or surveying

operations.• Notifying the Drilling and Completion Supervisor of any problems with the

surveying equipment that may invalidate results.

2.2.8 CONTRACTOR COMPETENCE ASSURANCEThe SDE and DS will ensure that all Directional and Surveying Contractor personnel will

have proven qualifications for the services they are contracted to provide to Eni-AgipDivision and Affiliates. Industrial experience, training and the educational background ofContractor personnel must comply with Eni-Agip Division and Affiliates specifications and/orlocal regulations and requirements for the job they are to perform.




3. WELL PLANNING PROCEDURE3.1. OBJECTIVES

All wells will be planned with due consideration given to the economic viability of the projectand surveying requirements with regard to accuracy and/or constraints (i.e. the accuracy ofavailable survey tools, the position and uncertainty of exact location of adjacent wells andthe difficulties expected in the drilling of the proposed well).The procedures outlined in the Surveying and Anti-collision sections of this manual willapply to all Projected Well Plots and, therefore, the Well Programmes.The prime reasons for specifying a well policy are to:

• Accurately plan every well on a consistent basis by ensuring that all requireddata is taken into consideration.

• Systematically and fully document the well planning process for each well.• Provide an accurate set of graphical output (plots) to monitor the well path while

the well is being drilled.

3.2. DEFINITIONS3.2.1. Vertical Well

In absence of other specifications (due to local policies or regulation's requirements) avertical well is a well whose planned target horizontal co-ordinates coincide with the OriginReference Point.

3.2.2. Deviated WellIs a well whose planned target horizontal co-ordinates are different from the OriginReference Point.

Note Considering that a prime objective of the Eni-Agip Division and AffiliatesSurveying Procedure is to accurately determine the well path position forall wells (exploration or development/vertical or deviated), in absence ofother specifications (due to local policies or regulatory requirements), avertical well will be classed as a deviated well if the inclination increasesduring the course of drilling the hole. It is vital to establish the minimumlevel of uncertainty in the event a relief well may be required.

3.2.3. Rotary Kelly Bushing (RKB)Is the horizontal level from which the well depth (and true vertical depth) will be measuredwhile drilling.It will differ from subsea depths by the height of the rig above sea level. It is also the pointfrom which the rig location is referenced. (Refer to Section 4.2)




3.2.4. Origin Reference Point (ORP)Is the origin which will be used for the horizontal co-ordinates e.g. latitude and departure ofthe well to be drilled. This will be the zero point on the horizontal well plan used to plot thewell while drilling.

3.2.5. Projected Well PlotIs the graphical representation of the well profile in the final approved form.

3.2.6. Directional Well ProgrammeIs the directional and survey requirements which will be included in the overall WellProgramme produced for the well.

3.3. PLANNING RESPONSIBILITIESThe SDE will be responsible for the accuracy and confirmation of data on the ProjectedWell Plots and Directional Well Programmes.The D&CM will have formal responsibility for the planning of the directional wells. The Eni-Agip Division and Affiliates Drilling & Completion Manager's approval will be required on allWell Programmes confirmed by signature.Amendments to the directional and surveying programme, after it has been finalised, will beassessed in compliance with the local Drilling & Completion Department’s organisation.Documentary approval for amendments will be required from the Eni-Agip Division andAffiliates Drilling & Completion Manager before they are implemented




3.4. PLANNING REQUIREMENTS3.4.1. Software Capabilities

The contractor’s software must be verified and then accepted by Eni-Agip Division andAffiliates prior to the work commencing.The following lists the minimum capabilities required for planning directional drillingcalculations and survey programmes:Well Planning Must have the capability for complex (3D) well paths with

graphical output facilities.Survey Calculation To calculate survey data and dogleg severity with the

Minimum Radius of Curvature (standard) methodInterpolation By single and multi-point interpolation by MD or TVD.Projection Multi-directional based on previous surveys.Trend Analysis Build/drop/turn required to hit any point on the target plane.Proximity Horizontal proximity and 3 dimensional calculation models

between two specified wells.Ellipse of Uncertainty To calculate in compliance with Eni-Agip Division and

Affiliates procedures (as described in Section 5.2).Anti-CollisionMonitoring

To calculate proximity to multiple wells with projectioncapability and tabular output of center-to-center distance,radius of uncertainty (ROU), distance between ROU andSeparation Ratio (See Section 5.3).

Geodetic Conversion To convert (both ways) between geographic and UTM co-ordinate systems.

GeomagneticConversion

To calculate local magnetic field strength, magnetic dip andmagnetic declination including rates of change with the latestcomputer models.

File Storage andProtection

Write protection and automatic virus protection capabilities forindividual files.

Data Acquisition By Magnetic media, software compatible with that used in thelocal Eni-Agip Division and Affiliates Department.




3.4.2. Decision ProcessThe decision process for approving a well prospect will be by the result of discussionsbetween various Eni-Agip Division and Affiliates departments.The Geology/Exploration or Reservoir Department will develop initial specifications e.g.target location and accepted displacement tolerance, TVD, lithology and expected TVD,total TVD of the well, geological constraints i.e. faults, dip angle, etc.The Drilling and Completion Department will produce an in-house well plot/plan forevaluation (possibly with direct input from contractor). The compiled data will then be usedto alter or finalise the geological specifications before final approval of the project.

3.4.3. Origin Reference Points (for well planning)Isolated wells The initial ORP will be the planned RKB location. This will

change to the actual location of the rig once its true position isconfirmed.

Template wells When planning directional wells to be pre-drilled from seabedtemplates, the ORP for the template will be the designatedtemplate centre, the ORP for each well will be the designatedslot.

Platform wells(1) When planning a directional well from an offshore fixedplatform, the ORP for the template will be the centre area slotor a designed slot. The ORP for each well will be thedesignated slot.

Note: When a platform has been installed over a template, and prior to drillingfurther wells, all definitive data for pre-drilled wells will be updated usingthe ORP as designated for platform wells above.

Onshore Cluster wells When planning a directional well from a cluster the ORP willbe the designated slot.

1 When a platform has been installed over a template, and prior to drilling further wells, all definitive data for pre-drilled wells will be updated using

the ORP as designated for platform wells above.




3.5. PRELIMINARY DIRECTIONAL PLAN INFORMATIONThe SDE will ensure that the Directional Contractor is provided with all data necessary foran initial well profile.When a drilling prospect requires a deviated well, a preliminary specification will beprepared by the SDE, with contribution from the Directional Contractor, if necessary. Thefollowing information will be specified:

• Surface and target co-ordinates - UTM or geographical• Local reference co-ordinates - platform centre, slot• Orientation of the wells bay (if applicable)• Displacement among the slots (if applicable)• Consider the wells position in the template, cluster, platform slots• Expected lithology - with a clear indication of subsea or RKB depths• Total well TVD - with a clear indication of subsea or RKB depths• Inclination at target• Shape and size of target(s) - restrictions, if applicable• Preliminary casing programme• Type of drilling fluid• Potential drilling problems which may affect the directional profile.• Definitive survey data of all well bores which may constitute a collision risk. This

will include all wells drilled from the same platform, cluster, template (includingabandoned sections of hole or plugged side-tracks) and appraisal wells in thesame area.

Note Confirm that all previously drilled appraisal wells in the area have beenincluded in the well plan information.

3.6. IMPACT OF THE RADIOUS OF UNCERTAIN (ROU)Before accepting the target location and size, some work should be carried out to estimate:

• The impact the ROU will have on entering or crossing formation/fault/blocks andhow those will impact on the well objectives.

• The impact the ROU will have on survey tool choice and relevant costs.

It is therefore important the SDE ensures that he obtains the necessary information from theExploration or Reservoir Department on the maximum acceptable size and shape of thetarget.If it is calculated that the ROU could fall outside the acceptable boundaries, the decision willneed to be made to either improve survey accuracy so as to reduce the ROU or decreasethe target size so the ROU's do not infringe into unacceptable zones.The cost implications must also be evaluated before making this choice.Once this matter is resolved the full directional planning can then be finalised. This is ofparticular importance when planning side tracks.




3.7. PROJECTED DIRECTIONAL PLAN INFORMATIONThe SDE will be responsible for ensuring that the directional and surveying plan including allthe available offset information is thoroughly researched.The Projected Well Plan will be reviewed by the SDE to ensure that it complies with theSurveying and Anti-Collision Procedure.The SDE will ensure the following information is correct before release to the DirectionalContractor for preparation of the Projected Well Plot:

• The ORPs are correct.• The well profile calculations are correct and reach the co-ordinates as

specified on the Well Plan.• The information described in section 3.5 is complete and correct.• The dogleg severity is within the maximum recommended (refer to the

Drilling Procedures Manual in absence of any local recommendations).

Note: The Directional and Surveying Plan should include the review of theposition of the well bore and extent of the ROU before entering thehydrocarbon bearing zone.




3.8. PROJECTED WELL PLOTSThe Project well plots must be full in compliance to Deviation Project of the ‘Well DrillingProgramme’.The SDE will be responsible for ensuring that the directional and surveying plan including allthe available offset information is thoroughly researched.The Projected Well Plan will be reviewed by the SDE to ensure that it complies with theSurveying and Anti-Collision procedure.The SDE will ensure the following information is correct before release to the DirectionalContractor for preparation of the Projected Well Plot:

Note The Directional and Surveying Plan should include the review of theposition of the well bore and extent of the ROU before entering thehydrocarbon bearing zone.

3.8.1. Well PlanA vertical and horizontal view of the well profile at all points is necessary where the well isdeviated. The minimum data as follows is required:

• Well Name, Field Name, Plan Version, Directional Contractor Name, Scales.• North Reference, Vertical Section Reference Azimuth, Declination Corrections.• Target Location with shape and tolerance clearly marked.• Co-ordinates of the ORP with Well centre and Targets listed.• Vertical Plan curve, labelled with critical directional points, casing points, and

primary formation tops.• Co-ordinates of critical points (as in the previous paragraph) - tabulated.• Authorisation box indicating ‘drawn by’, ‘checked by’, and ‘authorised by’ with

dates and signatures on all copies.




3.8.2. Spider PlotA scale horizontal plan view of all well bores that are considered to be potential collisionrisks is required. On a platform this will normally include all the slots.Practical scales will be required for all depths where a collision risk exists (i.e. 1cm = 1mmay be required for surface casing but 1 = 25m may be required to show all wells on theplatform to TD).A complementary listing of Proximity Data (as described in Section 5.3) will be supplied withall Spider Plots as required.The following data will be included on spider plots:

• Well Name, Field Name, Directional Contractor Name, Scale.• North Reference.• The ROU will be indicated for each well-bore at the same TVD where practical.• Co-ordinates of the ORP and all slots (listed relative to ORP).• Authorisation box indicating ‘drawn by’, ‘checked by’, and ‘ ‘authorised by’ with

dates and signatures.

3.8.3. Proximity EvaluationA plot relating the position of other well bores to the planned well at various depths isrequired (See Figure 3.5) complete with the data below:Well Name, Field Name, Directional Contractor Name, ScaleAuthorisation box indicating ‘drawn by’, ‘checked by’ and ‘authorised by’ with dates andsignatures.

3.9. DIRECTIONAL WELL PROGRAMMEThe SDE will be responsible for ensuring the accuracy of the directional plan informationand will perform a review of the directional well programme before its inclusion into the WellProgramme.The Directional Well Programme will conform to Eni-Agip Division and Affiliates proceduresas outlined in this manual.Any procedures which do not meet the standards of the Eni-Agip Division and Affiliatespolicies will be fully discussed and a separate approval will be required from the D&CMbefore proceeding with the programme.The D&CM will be required by signature to approve the Well Programme before itsdistribution.A copy of the directional and surveying requirements of the Well Programme will beforwarded to the rig or to the Directional Contractor before the commencement of directionaloperations.




Topics which will be contained in the Well Programme are:Surveying Requirements(Type of tools andsurveying frequency)

These must be specified for each section of the well andmeet the minimum requirements as specified in table 4.f andtable 4.g

Anti-Collision Analysis Proximity calculations as outlined in Section 5.3corresponding to each of the Spider Plots used. A summaryof the closest approach depth and distance for each well ofconcern will be included in the Well Programme. (Refer toSection 5.3)

Drilling Assemblies andBHA (Optional)

With expectations of performance

Optional SpecialEquipment (Optional)

Any non-standard equipment to be used in the drillingassemblies. The limitations of equipment to be used shouldbe specified if it has a bearing on operations

Previous Experience Recommendations based on previous experience will beincluded to help maximise operational efficiency. Potentialdrilling problems will be discussed, based on previousexperience

Torque/Drag Analysis(Optional)

Where justified, a projected torque and drag profile will beincluded in the well programme

Mud Programme It will be indicated if the mud type or properties has a bearingon directional or survey considerations

Drilling Parameters Limitations due to directional drilling requirements will behighlighted, if any

Finalised CasingProgramme

Actual depths will be based on the Final Well Plan




3.10. PRE-SPUD MEETINGPrior to the beginning of a well, a pre-spud meeting will be held between Eni-Agip Divisionor Affiliates and the Drilling Contractor and any of the relevant service contractors involved.The purpose of the pre-spud meeting is to discuss the well programme, with emphasis onimportant operational or safety issues.Both Eni-Agip Division or Affiliates and its contractors will take this opportunity to emphasiseparticular issues which concern them.Aspects of the well programme that require amendment are expected to be raised andresolved before drilling operations proceed.It is responsibility of the Drilling Superintendent or his delegate (normally the SDE) toorganise and chair the pre-spud meeting .The directional well programme will be reviewed at the meeting and the operationalrequirements and conditions will be discussed.If any points are raised which have a particular impact on the directional well programmethey, will be subsequently discussed by the SDE, Drilling Superintendent and DirectionalContractor.If any changes are required to the directional well programme it will be amended before thecommencement of the well or the commencement of the hole section concerned.If any significant changes are required to the directional well programme as a result of thepre-spud meeting, a formal programme amendment will be drafted and approved, in thesame manner as used for the Well Programme itself.

3.11. TECHNICAL MEETINGSPrior to the beginning of a well and during the course of operations, technical meetings willbe held between Eni-Agip Division or Affiliates personnel and the Directional Contractor. If aDirectional Contractor Technical Supervisor is provided, he must attend the meeting,otherwise a Contractor Directional Operator will be delegated.The purpose of the meeting prior the beginning of a well is to discuss the directional wellprogramme with emphasis on aspects which require to be discussed in greater depth thannormal on a well programme. In addition to technical aspects, organisation, logistics andmaterial supply along with any other relevant aspects are expected to be raised.In the course of operations, reviews and amendments to the Directional Well Programmeshould be carried out to conform with the actual situation. Important amendments should beassessed during the technical meetings (e.g. in a development platform, after CP wash outand Gyro survey records), A technical meeting should be held to assess possible changesof ORP, KOP, etc. Amendments will be approved as stated in Section 3.3It is the responsibility of the Drilling Superintendent or his delegate (normally the SeniorDrilling Engineer) to organise the technical meeting.




4. SURVEYING POLICY4.1. OBJECTIVES

All development wells will be surveyed from the wellhead to, at least, the lowesthydrocarbon bearing zone using the minimum guidelines specified in this section.All exploration wells will be surveyed from the surface conductor shoe to TD also using theminimum guidelines specified in this section.Surveying tool selection will be based on the anti-collision requirements, surveyingequipment accuracy, target size and depth.Survey accuracy objectives will be specified for each well.The prime reasons for specifying a well surveying procedure are to:

• Accurately determine the well path position versus previously drilled wells forproximity purposes and permit timely corrective action, e.g. correction run, wellshut in, plug back and re-drill.

• Accurately determine the well path position in the event a relief well is required.• Accurately determine the well bore position versus the planned profile and

permit timely corrective action, e.g. a BHA change or correction run if required.• Determine dogleg severity and permit timely corrective action, e.g. reaming, plug

back and re-drill.• Accurately determine the well position in relation to geological requirements.

4.2. DEFINITIONS4.2.1. Definitive Survey

Is the definitive or final survey which is obtained from the most accurate survey tool run inthe hole section, or from TD to surface for onshore wells, or to mudline for offshore wells.Several surveys tied together (concatenated) may be required to provide the definitivesurvey of the well e.g. from surface to 133/8" casing shoe - Ferranti FINDS; 133/8" shoe tillTD - NSG.

4.2.2. Origin Reference Point (ORP)Is the origin point of the well to be drilled, it is the datum to be used for the horizontal co-ordinates (latitude and departure).This will be the zero point on the horizontal well plan used to plot the well while drilling(Refer to Section 3.4.3)

4.2.3. Reference NorthIs the TRUE (Geographic) North. It is the reference for azimuth measurements and for theplotting of well co-ordinates .




4.2.4. Tie-In Point (TIP)Is the survey station (and spatial co-ordinates) from which further surveys will bereferenced.This will change during the course of drilling a well as more accurate surveys may be madeafter completing a particular hole section.

4.2.5. Foresight Reference (FR)Is the reference azimuth based on TRUE North which will be used for aligning gyro basedsurvey tools when they are run.It will normally depend on the surveyed rig heading as supplied by the rig positioningcontractor.

4.2.6. Dogleg Severity (DLS)Is the 3 dimensional curvature of the well bore normalised to a 30m interval. It will beexpressed in ‘degrees per thirty metres’ (ο/30m).The same definition holds for the expression of build and turn rates.

4.2.7. Magnetic DeclinationIs the correction which will be applied to the azimuth measurement of magnetic surveytools.This is necessary due to the difference in location between the earth's magnetic andgeographic poles.

4.2.8. Uncertainty Factor (UF)The UF is a coefficient, given in metres per thousand metres. surveyed, that reflects theincrease in radius of uncertainty of the well path with depth and depends only on the type ofsurvey instrument.They are reviewed and updated on a regular basis. A current list of UF is given in table 4.aand table 4.b

4.2.9. Magnetic Survey Tool ListMSS Magnetic single shot (film)MMS Magnetic multishotEMS Electronic magnetic multishotMWD Measurement while drillingHD High resolution dipmeter

4.2.10. Gyroscopic Survey Tool ListGSS Gyro single shot (film)GMS Gyro multishotSRG Surface reading gyroNSG North seeking gyro (FINDER)GCT Guidance continuous toolFINDS Ferranti Inertial Navigation System




Tool Type Inclination Range Error(M / 1,000M)

0ο/10ο 410ο/20ο 7

GSS/SRG/MS 20ο/30ο 1130ο/45ο 1845ο/60ο 300ο/20ο 2

20ο/30ο 3.5NSG/GCT 30ο/45ο 7.5

40ο/60ο 15.6FINDS 0ο/90ο 0.5

0ο/10ο 910ο/20ο 13

MSS/MMS 20ο/30ο 2030ο/45ο 4545ο/60ο 5560ο/80ο 600ο/10ο 2

10ο/20ο 2.2EMS 20ο/30ο 2.6

30ο/45ο 3.545ο/60ο 4.460ο/90ο 5.20ο/10ο 2.6

10ο/20ο 3.3MWD 20ο/30ο 4.3

30ο/45ο 6.345ο/60ο 8.560ο/90ο 10.5

Table 4.A - Survey Tool Horizontal Uncertainty Factor




Tool Type Inclination Range Error(M / 1,000M)

FINDS 0ο/90ο 0.50ο/10ο 2.5

10ο/20ο 3.7Magnetic 20ο/30ο 5.5

30ο/45ο 1045ο/60ο 15.360ο/80ο 17.30ο/10ο 2.2

10ο/20ο 2.7Gyro 20ο/30ο 3.5

30ο/45ο 5.745ο/60ο 7.8

Table 4.B - Survey Tools Vertical Uncertainty Factor4.3. SURVEYING RESPONSIBILITIES

The SDE will ensure that Directional Contractor personnel is supplied with the data requiredto perform the surveying operations at the rigsite.The (ORP) of the well will be confirmed by the SDE during the well planning phase (Refer toSection 3.4.3)The SDE will be responsible for providing documented confirmation of TIPs, FRs, andchanges in ORPs to the rig site and the Directional Contractor as required during the drillingoperation.The rig site DSR will be responsible for confirming that surveying tools have been run withinthe specified Quality Control procedures outlined in Section 4.6If surveying is subcontracted entirely to the Directional Contractor he will maintain primeresponsibility for the provision of surveying services to contract requirements.




4.4. SURVEYING REQUIREMENTSGeneral Surveying Requirements:

• All magnetic surveys will have to be reported after being corrected for magneticdeclination. Magnetic declination must be specified.

• For other surveys, ensure that magnetic declination is considered while aligning.• Gyro survey output does not need to be corrected for magnetic declination.• The depth of a survey is the survey instrument depth not the bit depth. This

applies to MWD and survey tools.• Azimuth will be referenced to true North.• Bottom hole location will be extrapolated from the last survey. This will normally

not be more than 30m. To confirm the bottom hole location the dipmeter can beused as it can survey down to around 5m from TD if hole conditions allow.

• For drilling purposes ‘depth’ will always be quoted as drilled depth and notconfused with wireline depth.

4.4.1. Approved Surveying ToolsThe approved tools for surveying well bores are listed in the definitions Section 4.2.9 and4.2.10.

4.4.2. Software CapabilitiesThe software package described in Section 3.4.1 will be required to calculate and fullyevaluate well survey data.

4.4.3. Survey Calculation MethodEni-Agip Division and Affiliates standard survey calculation method will be Minimum Radiusof Curvature.This method is considered the most accurate representation of well bore position, providedsurveys are taken with the frequency detailed in the surveying procedure.

4.4.4. Survey Tool UncertaintyThe horizontal and vertical error of survey tools will be documented for future reference.The specification is given in terms of a coefficient in m/1,000m.The current values are given in table 4.a for horizontal and table 4.b for vertical wells

4.4.5. Minimum Surveying ProgrammeThe basic surveying requirements for vertical and deviated wells are outlined in table4.f(vertical) and table 4.g(deviated).This represents the current minimum Eni-Agip Division and Affiliates requirement for wellsurveying programmes and will be exceeded if conditions warrant.




4.4.6. Accuracy Comparison MethodsData from different survey instruments will be compared in one of two ways:

• The horizontal distance between points versus the number of metres surveyedpermits comparisons with expected uncertainty factors.

• The comparison of the inclination and azimuth versus depth (‘T’ charts) permitsthe determination of the average difference between instruments.

4.4.7. Azimuth ReferenceAll survey data reported to Eni-Agip Division and Affiliates will be required to have azimuthspre-corrected to TRUE North.This requires magnetic based surveys to be corrected for magnetic declination. Gyro basedsurveys do not require a correction.

4.4.8. Tie-In PointsContinuous survey instruments will have a specified station to be used as a tie-in point forsubsequent data.Generally it will be the deepest survey station of the run. Exceptions are indicated inSection 4.34

4.4.9. Measurement SystemThe system of units to be used will be specified by the Contractor and approved by Eni-AgipDivision and Affiliates.

4.4.10. Horizontal Uncertainty FactorsThe values displayed in table 4.a will be used in the calculation of the horizontal positionuncertainty of survey tools.These values are given in metres per thousands metres of hole surveyed and will berevised as required. An example calculation is shown for reference in Section 5.9.

4.4.11. Vertical Uncertainty FactorsVertical errors are generally smaller than horizontal errors and do not require considerationunless hole inclination is above 70ο from horizontal.The values displayed in table 4.b can be used in the calculation of the vertical positionuncertainty of survey tools. These values are given in metres per thousand metres of holesurveyed and will be revised as required.




4.4.12. Magnetic DeclinationThe magnetic declination will be individually calculated for each new well location.Since it is a time based measurement, the date used for the calculation will be an estimatedmid-point for the drilling operation period. Subsequent surveys will require the re-calculationof magnetic declination if taken more than six months after the well is drilled.

4.4.13. Rigsite Directional Data RequirementThere will be a pre-requisite data requirement to calculate and plot the correct well boreposition at rig-site.The following data will be supplied to the directional drilling contractor via the Projected WellPlot and Well Programme (as specified in Sections Errore. L'origine riferimento non èstata trovata. and 3.9) before directional operations commence:

• ORP co-ordinates with respect to Geographical, UTM.• Slot location co-ordinates with respect to Geographical, UTM.• Target co-ordinates with respect to Geographical, UTM .• Magnetic declination at the rig-site location.• The most recent approved tie-in point, if applicable (SDE to provide documented

confirmation).• Projected Well Plots as required.




4.5. CONSIDERATIONS FOR SURVEY TOOL SELECTION4.5.1. Directional Drilling Control

Controls of the wellpath is based on directional techniques involving the use of specialBHA’s to build, drop or hold angle. To confirm that the well bore is achieving the desiredprofile, measurement of borehole position while drilling is required.Surveying tools commonly used for directional drilling control are listed in the followingtable:

Tool Application Limitation

MSS/MMS Single-shotMulti-shot

Temperature limitation.Requires interpretation of film upon developing.Time limited by amount of film available with MMS.

MWD Survey while drilling Temperature limitation.ST Kick-off in high

temperature zoneRequires conducting wireline.

EMS Single-shotMulti-shot

Temperature limitation.

GSS/GMS Single-shotMulti-shot

Requires interpretation of film upon developing.Requires gyro drift check.Requires a reference to determine direction.Time limited by amount of film available with (GMS).

SRG Single-shotMulti-shot

Requires conducting wireline for surface readout.Requires gyro drift check.Requires reference to determine direction.

NSG/GCT Single-shotMulti-shot

Requires conducting wireline.Requires on-site calibration and final instrument check.

Table 4.C - Survey Application For Directional Drilling Control Centre




4.5.2. Well profile VerificationThe objective of this survey category is to provide an accurate well bore position, fromwhich a ‘benchmark’ survey can be established for the comparison of all other directionalsurveys taken.Redundant surveys can provide an extra measure of reliability in critical well operations,such as multi-well platforms or relief well drilling.Types of position verification surveys are:QC surveys Known values of magnetic dip angle and field strength are

employed as a ‘check’ to confirm survey data collected.Overlap surveys Taken going into and coming out of hole.Reference surveys Used to establish the ‘benchmark’ against which all

subsequent survey data is compared.Verification surveys Run after MWD to confirm results of initial survey.Final Position surveys Determine the actual final position of the wellbore




Surveying tools commonly used for position verification are listed in the following table:Tool Application Use

MSS/MMS MWD verification Verifying inclination and direction of MWD.Inclination only Checking inclination of surface hole section before setting

casing.Toolface Establishing check for MWD or ST readings.

Well profile Defining well bore path at a given depth.GSS/GMS MWD toolface GSS can verify toolface position in area with magnetic

interference.Well profile Checking of the well path after casing is set. (GMS used

through casing after well is drilled using MSS.)NSG Well profile Confirming of MSS / MMS or MWD after casing is set.

Multi shot survey Confirming well path or orientation when high horizontalaccuracy is required.

Redundant survey Completing survey on in-run and out-run for confirmation ofaccuracy.

SRG MWD toolface Verifying toolface position in area with magneticinterference.

Well profile Checking of the well path after casing is set. SRG usedthrough casing after well is drilled using MSS.

EMS Well profile Confirming MSS/MMS or Steering Tool.

FINDS Surface surveyProviding a baseline for comparison of all subsequentsurveys.105/8” OD tool limits use to large size casing only.Limited to 31/2 hr memory only.

Table 4.D - Survey Application For Well Profile Verification




4.5.3. Orientation SurveysOrientation surveys may be required in operations which require determination of the knowndirection, related to, either, true or grid North. Operations requiring tool orientation include,setting packers in cased hole, aligning bent subs on a downhole motors, running jettingdevices, positioning whipstocks for side tracking and aligning perforating guns.Surveying tools commonly used for position verification are listed in the following table:

MAGNETIC TOOLS GYRO TOOLS

MSS Bent subsJetting device GSS/GMS

WhipstockPackersTemplates

MMSBent subsJetting deviceOrienting Coring

SRG/NSG

WhipstockPackersTemplatesPerforating gun

ST Bent subsjetting device

EMS Bent subsOrienting Coring

Table 4.E - Survey Application For Orientation




General notes for survey tool selection :

Maximum inclination Survey accuracy requirement will differ between vertical anddeviated wells.

Casing size FINDS inertial surveying system can be run only in 133/8"casing or larger.

Survey depth GSS will not be run deeper than 400m due to excessive driftrates

Hole inclination Maximum inclination for GSS, GMS and SRG is 70Ο (stabilitylimit).

Potential drilling problems Differential sticking problems precludes the use of wirelinebased surveys with drillpipe in open hole (GSS, SRG, MSSand EMS).

High pressure reservoirs In an isolated deviated well, GMS or SRG will be run in theprevious casing to establish minimum uncertainty beforedrilling through a high pressure zone (in case of a blow outand a relief well is required). A more accurate tool(NSG/GCT) may be used for accuracy improvement.

Temperature Limitation Maximum borehole temperature must be within specificationfor the survey tools proposed for the programme.

Well Proximity Template/platform wells which are drilled in theneighbourhood of other wells must maintain a minimumseparation with respect to the other wells. This may requireadditional surveys (e.g. NSG in drill pipe) more often thanwith individual wells.

Survey Accuracy Installations will be most crowded immediately below theplatform/template and will require greater survey accuracy tofix well bore locations. The most accurate tools (FINDS orNSG) may be necessary for minimum uncertainty in criticalsituations.

Magnetic Influence Magnetic based surveying instruments will not be used, inany situation, as the prime source of well location calculationswhen within 8m of any adjacent casing string.

Target Size and Depth The accuracy of the surveying tools used on a well will besuch that the total horizontal uncertainty at target depth isreasonable compared to the target size. The smaller and thedeeper the target the more stringent the survey requirements.




4.6. QUALITY CONTROL (QC)4.6.1. Magnetic Survey Tools (at Rig-site)

All magnetic tools will be run in non-magnetic BHA environments.Magnetic azimuth values will be considered invalid when the survey instrument is within 8mof an adjacent casing shoe:

NMDC RequirementsMagnetic instruments must be run inside a sufficient length of NMDC.In absence of any local Affiliates procedures, or Directional Contractor requirements, thelength of NMDC can be determined using graphs from Drilling Procedures Manual (Refer tothe Directional Drilling sub-section on ‘ Magnetic surveys’).

Compass SpacingIn absence of any local Affiliates procedures, or Directional Contractor requirements, thelength of NMDC can be determined using graphs from Drilling Procedures Manual (Refer tothe Directional Drilling sub-section on ‘Magnetic Surveys’).StabilisersNon-magnetic stabilisers will be the only type permitted for use between NMDC's. Ferroussteel stabilisers are unacceptable.Magnetic Single Shot & Electronic Multi ShotIn absence of any local Affiliates procedures, or Directional/Surveying Contractorrequirements refer use from suggestions made in the Drilling Procedures Manual (Refer tothe Directional Drilling sub-section on ‘Magnetic Surveys’).

Measurement While DrillingWhen magnetic influence is expected from adjacent casing (or when the well is separatedless than 8m horizontally from an adjacent casing string), provision will be made to run agyro based survey tool on top of the MWD.MWD tools will be capable of transmitting data to surface indicating the presence ofmagnetic interference or data which can be processed at surface (also indicating thepresence of magnetic interference).A shallow depth functional test of the tool in the string will be performed on each trip into thehole.Survey repeatability should be within 0.5ο inclination and 2ο azimuth (above 10ο inclination).In directional wells, a benchmark, or reference survey, is recommended to be taken in eachhole section below the casing shoe in magnetically free environments at the firstopportunity. This permits a comparison survey at this point when running into the hole withsubsequent MWD tools.




A check survey will be taken immediately off bottom before starting a new bit run forcomparison with the previous run.The tie-in point will be the deepest reported surveys station from the previous hole section.

4.6.2. Gyroscopic Survey Tools (at Rig-site)Gyroscopic tools require accurate alignment of the instrument on the foresight/referenceazimuth.(Refer to Section 4.2.5)Care must be taken in vertical or low inclination holes for the proper centralisation of theinstrument, especially in large diameter casing.Corrections will be made for the drift workrate (the natural precession of the gyro with time)in non ‘North Seeking’ gyro tools:

Gyro Single ShotThe landing slug will be checked to confirm seating on each run.Time elapsed between two drift checks will not exceed 15min.GSS will not be run below 400m.

Gyro Multi Shot Surface Reading GyroThe landing slug will be checked to confirm seating on each run.Time elapsed between two drift checks must not exceed 15min.Drift rate will not exceed 10ο/hr.Repeat surveys at the same point and orientation must agree within 0.5ο for inclination and5.0ο for azimuth.It will be necessary in some situations, when using a bent sub BHA, to make a series ofsurveys with various orientations at one depth to establish an accurate measurement. Thisis called a ‘cluster shot’ or a ‘rotational shot’. A cluster shot will be required while surveyingwith SRG to establish an accurate measurement if using a bent sub assembly.

North Seeking GyroINRUN/OUTRUN inclination must agree to within 0.25ο.INRUN/OUTRUN azimuth must agree to within 1.0ο for an inclination greater than 10ο andwithin 5ο for an inclination lower than 10ο.The tie-in point will be the last surveys station from the INRUN.




4.6.3. Schlumberger ‘Guidance Continuous ToolThe maximum running speed is 1,800m/hr. (inclination<10ο) increasing to 4,500m/hr. indeviated hole above 20ο inclination.Drift checks will be required at each end of the survey and will not exceed 0.2ο/hr.INRUN/OUTRUN inclination will agree within 0.25ο.INRUN/OUTRUN azimuth will agree within 1ο for inclinations over 10ο.The tie-in point will be the best fit of the last 4-5 surveys from the INRUN.

4.6.4. Ferranti Inertial Survey ToolRecommended running speed will be 75m/minIf the running speed falls below 25m/min the run will be aborted.The tool will be run with alternate 1min. fixed and 1min. transit intervals.INRUN/OUTRUN results must agree within 1metre per thousand metre of measured holedepth.Successive FINDS surveys on the same well must agree within 2metres per thousand metreof measured hole depth.The tie-in point will be the third last station from bottom from the INRUN.

4.6.5. In-House Quality ControlThe quality assurance procedures of the surveying company (including MWD) should berequested at the beginning of a contract. These would include the bench mark checks thattake place prior to the tool being shipped, the rig site checks before during and after thesurvey run and the subsequent follow up checks when the tool is returned to the servicecompanies base.These should be evaluated and if any points of concern are raised, a plan should be agreedbetween Eni-Agip Division and Affiliates and the service company for the alteration ofprocedures to avoid any further QC concerns.Details of any rig site checks should be passed on to the Drilling Supervisor by the SDE.As a method of assurance the service company should include a check list of checkscarried outwith the presentation of the survey results to the SDE.




4.7. SURVEY PROGRAMME FOR VERTICAL HOLEStable 4.f outlines the standard minimum survey programme for vertical exploration wells.TOTCO will be acceptable only on surface holes if inclination is less then 1.5ο.MSS is the standard. MWD will be run as the survey tool of choice, if economically andtechnically justified.If MWD is used at the recommended frequency and the wellpath is clear of other wells,cased hole surveys may be omitted (if it is not dictated by local condition, legislation or thirdparties).Survey tool requirement will be dictated by collision risks assessment.Survey frequencies are a minimum guideline. Survey intervals will be reduced as necessaryto meet the anti-collision policy as described in Section 5 or if drilling conditions dictate.

4.8. SURVEY PROGRAMME FOR DEVIATED HOLEStable 4.aG outlines the standard minimum survey programme for directional wells.TOTCO will be unacceptable at any stage of the well. All surveys require an azimuth and aninclination measurement.MWD is the standard. MSS will be run as the survey tool of choice, if economically andtechnically justified.If MWD is used at the recommended frequency and the wellpath is clear of other wells,cased hole surveys may be omitted (if it is not dictated by local condition, legislation or thirdparties).In cased holes GMS is the standard. The FINDS tool is the most accurate survey toolavailable. Platform planning is greatly improved by its use. If anti-collision is a criticalconcern the NSG/GCT or the FINDS will be used.Survey tool requirement will be dictated by collision risks assessmentSurvey frequencies are a minimum guideline. Survey intervals will be reduced as necessaryto meet anti-collision policy as described in Section 5 or if drilling conditions dictate.Survey frequencies of vertical phases of individual deviated wells will be reduced at thesame value utilised for vertical wells.




Platform/Cluster/Template Individual WellsDuring Drilling After Casing Set During Drilling After Casing Set

Type ofinstrument

Frequencyof use

Type ofinstrument

Frequencyof use

Type ofinstrument

Frequencyof

instrument

Type ofinstrument

Frequencyof use

30” CPTocto

(template) BottomGMS/SRGRefer tonotes

30mMSS

Toctco at shoe

20” - 133/8”Surface CSG

MWDMSS

30m60m

GMS/SRGNSG/GCTRefer tonotes

30m MWDMSS/ Toctco

150m (andeach trip)

133/8 CSG(Intermediate)

MWDMSS 30m


30m MWDMSS

150m (andeach trip)

95/8 CSG MWDMSS 30m


30m MWDMSS

150m (andeach trip)

7” CSG MWDMSS 30m


30m MWDMSS

150m (andeach trip)

5” Lin MWDMSS as required


30m MWDMSS

150m (andeach trip)

1. May be omitted if it is not dictated by local conditions, legislation or third party contractors procedures and the well is clear of other wells and if goodsurveys (MWD) have been taken in open hole.

2. MSS or HDT allowed below top of lowest pay zone (in open hole).3. FINDS to replace gyro if available.4. In hot wells there may not be enough room for the gyroheat shield. In such cases run a magnetic multi-shot prior to running the casing.5. When conductors have been driven, all conductors should be cleaned out and gyro surveyed prior to drilling the first well.6. NSG/GCT can replace GMS if high horizontal accuracy is required for anti-collision purpose.

Table 4.F - Frequency and Types of Surveys for Vertical Wells




Platform/Cluster/Template Individual WellsDuring Drilling After Casing Set During Drilling After Casing Set

Type ofinstrument

Frequencyof use

Type ofinstrument

Frequencyof use

Type ofinstrument

Frequencyof

instrument

Type ofinstrument

Frequencyof use

30” CPTocto

(template) BottomGMS/SRGRefer tonotes

30mMSS

Toctco at shoe1

GMS/SRG 30m

20” - 133/8”Surface CSG

MWDMSS

30m60m


30m MWDMSS/ Toctco

30m7

60m71

GMS/SRG 30m

133/8 CSG(Intermediate)

MWDMSS 30m


30m MWDMSS

30m7

60m71.5

GMS/SRG 30m

95/8 CSG MWDMSS 30m


30m MWDMSS

30m7

60m71.5

GMS/SRG 30m

7” CSG MWDMSS 30m


30m MWDMSS

30m7

60m71.5

GMS/SRG 30m

5” Lin MSS/MWDHDT/MMS3 as required


30m MWDMSS

30m7

60m7

1. May be omitted if it is not dictated by local conditions, legislation or third party contractors procedures and the well is clear of other wells and if goodsurveys (MWD) have been taken in open hole.

2. Can use MWD/ST/MSS/MMS when there are problems getting gyro down or when inclination is more than 70O

3. MSS or HDT allowed below top of lowest pay zone (in open hole).4. FINDS to replace gyro if available.5. In hot wells there may not be enough room for the gyroheat shield. In such cases run a magnetic multi-shot prior to running the casing.6. NSG/GCT can replace GMS if high horizontal accuracy is required for anti-collision purpose.7. For vertical phases the survey frequency shall be considered as per vertical wells (150m and each trip).

Table 4.G - Frequency and Types of Surveys for Deviated Wells




5. ANTI-COLLISION PROCEDURE5.1. OBJECTIVES

All development wells will be surveyed from the wellhead to, at least, the lowesthydrocarbon bearing zone using the minimum guidelines specified in this section.Anti-collision procedures will be implemented, in all cases where is a potential collision riskaccording to the policies outlined in this manual.The prime reasons for specifying an anti-collision procedure are to:

• Ensure a consistent method is used to evaluate and reduce collision risksbetween wells.

• Establish a common procedure for developing multi-well sites which takes intoaccount actual well trajectory and trajectories of already existing wells.

• Establish a common procedure that discriminates between interference fromcompleted/producing wells and plugged/abandoned/uncompleted wells.

5.2. DEFINITIONS5.2.1. Ellipsoid of Uncertainty

The Anti-Collision Model currently used by Eni-Agip Division and Affiliates is based on anEllipsoid of Uncertainty concept which describes the location of the well bore at any depth interms of a probability volume determined from the errors in the equipment used to surveythe well.In general, the most conservative probability volume at any depth is in the shape of asphere, therefore the uncertainty on the location of the wellbore at any depth can bedescribed by the ‘Radius of Uncertainty’ concept. (Refer to Section 5.2.2 below)

5.2.2. Radius of Uncertainty (ROU)The ROU is the radius of a sphere, at a specific vertical depth, which has the probability ofcontaining the well path. It is a cumulative calculation based on the product of theHorizontal Uncertainty Factor of the survey instrument used to that point and the surveyeddepth to that point .In field site calculations, the ROU will be increased by an amount depending on the ‘DoglegPotential’ (Refer to Section 5.2.3 below) along a projection from the last survey point to alower depth of interest (e.g. TD of the section or the expected closest approach to anotherwell).

5.2.3. Dogleg Potential (DLP) and Dogleg Severity (DLS)Every BHA run in a hole has a maximum expected dogleg capability, whether steerable ornot. In the case of rotary assemblies the DLS will be based on historic performance of theassembly on the current well. In the case of steerable assemblies it will be based on theDirectional Contractor recommendation.




5.2.4. Horizontal Uncertainty Factor (UF)The UF is a coefficient, given in meters per thousand meters surveyed, that reflects theincrease in radius of uncertainty of the well path against depth and depends only on thetype of survey instrument and on the hole inclination. A current list of UF is given in table4.a

5.2.5. Current Well (CW)The well being planned or drilled. (See figure 5.a)

5.2.6. Target Well (TW)Any well being considered for anti-collision purposes or proximity calculations. (See figure5.a)

5.2.7. Separation Distance (SD)The SD is the distance, in the plane of the expected closest approach, between ROU of theCW and the TW at a given vertical depth. (See figure 5.a)

5.2.8. Centre to Centre Distance (CCD)The CCD is the distance, in the plane of the expected closest approach, between thecentres of CW and TW paths at a given vertical depth. (See figure 5.a)

5.2.9. Separation Ratio (SR)The SR is the ratio of CCD to the sum of the ROU's. (See figure 5.a)




Figure 5.A - Relationship of Well Bore Uncertainties

CW = Current Well TW = Target Well

SD = Separation Distance

ROU = RADIUS of UNCERTAINITY

CCD = Centre to Centre Distance

SEPARATION RATIO ( SR ) = CCDCW ROU + TW ROU

SEPARATION DISTANCE (SD ) = CCD - ( CW ROU + TW ROU )

SEPARATION RATIO ( SR ) > 1 = NO INTERFERENCE BETWEEN ROU's

SEPARATION RATIO ( SR ) < 1 = INTERFERENCE BETWEEN ROU's




Definitions for figure 5.b:Curve A: Threshold of separation

Is the curve where, at any depth, the condition SR = 1At any depth defines the distance of potential collision.

Curve B: Threshold of alertIs the curve where, at any depth, the condition SR = coefficient BUsually coefficient. B = 1.5

Curve C: Threshold of dangerIs the curve where, at any depth, condition SR = coefficient CUsually coefficient. C = 2

Zone X: Field of dangerThe field between Curve C and Curve B

Zone Y: Field of alertThe field between Curve B and Curve A

Zone Z: Field of Potential CollisionThe field delimited by Curve A

The values of coefficients B and C could be reduced on the basis of a probabilistic analysisof the occurrence of potential well collision situations. The Uncertainty Area Ratio (UAR)concept could be used to evaluate the probability of the occurrence of potential wellcollision situations. The UAR is the ratio of the sum of the two Uncertainty Area to the sumof the two hole sizes.

( ) ( )[ ]( ) ( )[ ]22

22

TWODCWODTWROUCWROU2UAR

+

+=

where:CWOD = the outside diameter of the current wellTWOD = the outside diameter of the target well

In the following table is reported an example of reduction of the coefficients to determinatethe threshold of alert and the threshold of danger (previously indicated as ‘Coefficient B ‘and ‘Coefficient C’) on the basis of UAR value :

UAR Coefficient B Coefficient C< 20,000 1.50 2.0 40,000 1.45 1.9 60,000 1.40 1.8 80,000 1.35 1.7

100,000 1.30 1.6 120,000 1.25 1.5>120,000 1.25 1.5

Table 5.A - Example of Reduction of Coefficients




Figure 5.B - Well Proximity Evaluation




5.3. ANTI-COLLISION REQUIREMENTS5.3.1. Software Capabilities

The software package previously described in Section 3.4.1 will be required to calculate andfully evaluate well survey data.

5.3.2. Projection Technique (with Rotary Assemblies)Evaluating the collision risk of the CW invariably involves a forward projection to account forexpected drilling assembly behaviour below the last survey point.The projection will be made on CW accounting for the expected closest approach to theTWs. The trend observed in the final surveys of a rotary assembly will be used to establishthe expected trajectories.

5.3.3. Projection Technique (with Steerable Assemblies)Evaluating the collision risk of the CW invariably involves a forward projection to account forexpected drilling assembly behaviour below the last survey point.The projection will be made on CW accounting for the expected closest approach of theTWs. With steerable assemblies, it will be possible to assume a trend based on a maximumDogleg Potential of the assembly in a desired direction.

5.3.4. Worst Case Projection TechniqueIn the worst case condition (e.g. when the projected dogleg is unknown or cannot beextrapolated for certain) an additional uncertainty factor due to the maximum DoglegPotential of the assembly, will be added to the applicable ROU.For projection purposes, maximum Dogleg Potential (inso/30m) will be translated as followsinto an addition to the ROU of the Current Well for each 30m drilled [ = sine (DLP) x 50]:

Maximum Dogleg Potential Additional ROU/30m1°/30m 0.27m2°/30m 0.55m3°/30m 0.79m4°/30m 1.07m5°/30m 1.34m

Table 5.B - Maximum Dogleg Potential versus Addition to ROUThe intervals where the separation is planned to be less than the threshold of danger(zone X) or the threshold of alert (zone Y), will be reported (specifying Vertical depths andMeasured depths) in the Well Programme and in the Directional Well Plan before directionaldrilling operations commence.It is recommended that a graphical representation, like the one shown in figure 5.c, is to beattached for each identified zone.




The original wellhead co-ordinates and elevations, especially for older wells, should bechecked for potential errors. There may be a more recent survey of the wellhead locationthan is quoted on the original survey data. The difference, if any, between the two must beassessed and the necessary recalculation of the data performed.Magnetic based surveying instruments will not be used as the prime source of CW locationcalculation within 8m of any TW (centre to centre distance). A gyro based surveying tool willbe used as the primary survey instrument until magnetically calculated azimuths agree withthe gyro tool .

Figure 5.C - Uncertainty Area Ratio

0 20 40 60 80 100 120

AGO 29 - AGO 17 AGO 17 - AGO 29

VERT

ICAL

DEP

TH (m

)

1000

2000

3000

40000

0




5.4. CONSIDERATIONS IN PLANNING A NEW MULTI-WELL SITEThe allocation of ‘wells to slot’ from a multi-well site will be planned in order to limit potentialwell collision situations. Points to be considered are:

• Well to slot allocation should avoid crossing of well trajectories wheneverpossible.

• The slot allocations will account for final target displacement and direction.Higher displacement wells will be drilled from the outer slots whenever possible.

• The kick-off points of wells will be spaced vertically depending on final targetdisplacement. Larger displacement wells will be kicked off at shallower depthswhenever possible.

• If crossing of trajectories is unavoidable, the tangent section on both wellsshould be achieved while drilling whenever possible.

• The drilling order of wells will be such that the eventual shut-in time requirementof adjacent wells is kept to a minimum.

• Spacing of wells for the surface vertical phases will not be subjected to SR < 1limit, in case drilling is planned/performed from a multiwell site where all thesurface phases have to be drilled subsequently at once time.

• Anti-collision procedures will apply, for the surface vertical phase, in case drillingis planned/performed from a multiwell site where production from adjacent wellsis on going or during any production while drilling activity.




5.5. ANTI-COLLISION RESPONSIBILITIES5.5.1. Planning Wells (with interference between existing producing/completed wells and

new wells)a) The D&CM will have overall responsibility for the maintenance of safe

operations while drilling in proximity to other wells.b) Directional Well Plans in which trajectories fall into zone X is only allowed when

the target well (TW) has been properly plugged.c) The SDE will define any CWs falling within zone X, during the well planning

stage and will prepare necessary recommendation according to the followingguideline:• The TW directional data must be of reliable source and quality.• Planning the CW, relevant anti-collision analysis have been performed.• Proximity calculation and projection are conducted regularly at the wellsite

while drilling the CW in order to confirm the CW position within zone X.• While drilling within zone X to assure adequate quality and frequency of

the surveys, MWD will be used.d) The SDE will prepare a contingency plan for plugging the appropriate TWs.e) The contingency plan will specify procedures, timing and responsibilities of other

Eni-Agip Division and Affiliates departments in suspending the appropriate TWsand will be included in the well programme for the CW. (Refer to Section 5.7)

f) Planning directional wells in which trajectories fall into the zone Y are notallowed as a part of normal procedure.

g) Dispensations will require approval by the D&CM and must be clearly stated anddocumented. (Refer to Section 1.3).

h) If the separation is projected to fall within the zone X during drilling operations,when this has not been planned, drilling will be alerted and the SDE will preparea recommendation for plugging the necessary TW(s) as stated in Section 5.76.Approval will be required from the D&CM to proceed drilling.

i) When the separation is projected to fall within zone X, the Drilling Supervisor(rigsite) will be responsible to ensure appropriate action is taken to shut-in theTWs, before drilling operations proceed. (Refer to Section 5.76)

j) The Eni-Agip Division or Affiliates SDE will confirm anti-collision calculationsmade at the rig-site on a survey by survey basis when the separation is inferiorto the threshold of danger (i.e. be within zone X).

k) If the separation is projected to fall within zone Y during drilling operations,drilling operations will be stopped (Refer to Section 5.8). Documented approvalwill be required from the D&CM for corrective procedures before drilling isallowed to proceed. (Refer to Sections 1.3 and 5.8)

l) The DSR (rig-site) will be responsible for suspending drilling operationsimmediately when the separation is projected to fall within zone Y (or isprojected to fall within zone Z if it was allowed within zone Y).

m) The DS will responsible for implementing the appropriate corrective actions asapproved by the D&CM before drilling operations proceed. (Refer to Section 5.8)

n) Planning and drilling with separation falling in the zone Z is unacceptable underany circumstance.




5.5.2. Planning Wells (with interference between existing, non completed/P&A wells andnew wells)

a) The D&CM will have overall responsibility for the maintenance of safeoperations while drilling in proximity to other wells.

b) Planning new wells within zone Y is allowed when the target well (TW) is aplugged and abandoned, suspended or an uncompleted well.

c) Planning and drilling with separation falling in the zone Z is unacceptable underany circumstance.

d) During the well planning stage, the SDE will define any CWs falling within thezone Y and will prepare necessary recommendation according to the followingguideline:• The TW directional data must be of reliable source and quality.• Planning the CW, relevant anti-collision analysis have been performed.• Proximity calculation and projection are conducted regularly at the wellsite

while drilling the CW in order to confirm the CW position within the zone Y.• While drilling within zone Y to assure adequate quality and frequency of

the surveys, MWD will be used.e) If the separation is projected to fall within zone Y during drilling operations,

where this has not been planned, drilling will be alerted and the SDE willprepare recommendations for drilling procedures as stated before.

f) The Eni-Agip Division or Affiliates SDE will confirm anti-collision calculationsmade at the rig-site on a survey by survey basis when the separation is inferiorto the threshold of alert (i.e. within zone Y).

g) If the separation is projected to fall within zone Z during drilling operations,drilling will be stopped. Documented approval is required from the D&CM forcorrective procedures before drilling is allowed to proceed. (Refer to Sections1.3 and 5.8)

h) The DSR (rig-site) will be responsible for suspending drilling operationsimmediately when the separation is projected to fall within zone Z.

i) The DS will responsible for implementing the appropriate corrective actions asapproved by the D&CM before drilling operations proceed. (Refer to Section 5.8)




5.6. PLUGGING OF COMPLETED TARGET WELLS (when separation is in zone x)The following procedure will apply at all times when the well programme calls for aseparation less than the threshold of danger (within zone X) or the separation is projectedto fall within zone X:

a) Any TW which separation is projected to be less than the threshold of danger(i.e. within zone X) above the sub-surface safety valve (SSSV) depth less 30m,must have the SSSV closed and the well de-pressurised.

b) Any TW which separation is projected to be less than the threshold of danger(i.e. within zone X) below the SSSV depth less 30m compared to the plannedCW, is to be plugged at least 150m below the lowest depth in zone X for theTW.

c) After Installation of the plug, all TW pressures will be bled down to zero, orcirculated to the appropriate kill weight fluid before drilling commences on theCW.

d) Target Wells will be only brought on line when the separation is greater than thethreshold of danger (i.e. outside zone X) and increasing steadily.

5.7. SUSPENSION OF CURRENT WELL (when separation is in zone y or in zone z)The following procedure will apply at all times when separation, while drilling, is projected tobe less than the threshold of alert (i.e. within zone Y) or less than the threshold of danger(within zone Z) depending if the CW is drilled in accordance with Sections 5.5.1 or 5.5.2(See figure 5.f)

a) When the separation to any TW is projected to be less than the applicablethreshold, the Drilling and Completion Supervisor will be advised and drilling ofthe CW will be stopped.

b) The SDE will formulate a plan of action after considering the following options:• Re-survey the CW and/or TW with a more accurate survey tool to reduce

its ROU and increase the projected separation to an acceptable level.• Make a trip to alter the well-path of the CW with an orientable (bent sub or

steerable system) BHA to increase the projection of separation ratio to anacceptable level.

• Plug the well and side-track at a depth where the well can be safely re-drilled.

c) Operations will only resume after the proposed corrective actions have beenapproved by the D&CM.

d) A well planned or drilled with separations less than the threshold of separation(i.e. within zone Z) is unacceptable under any circumstance.




5.8. WELL-SITE PROCEDURES1) Magnetic based surveying instruments will not be used as the prime source of CW

location calculation within 8m of any TW (centre to centre distance).2) When magnetic influence is suspected, gyro surveys will be run to check the magnetic

surveys until such time as the magnetic and gyro survey tool azimuths agree within 2ο

azimuth for at least two or more consecutive surveys.3) When proximity is critical with a steerable assembly, the MWD will be placed on top of

mud motor to ensure the survey is as close as possible to the bit.4) When there is any doubt about the accuracy of a magnetic based survey, it will be

double checked with a gyro based tool before drilling ahead.5) Proximity calculations will be done at regular intervals depending on the risk of

collision but, in any case, at least twice daily while drilling.6) Only the most experienced Directional Contractor personnel will be utilised when

proximity situations are expected to be of concern during drilling operations. If drillingconditions call for additional personnel to cover 24hrs basis service, actions will beimplemented accordingly agreed with the Contractor.

7) The following precautions will be observed when CWs are within zone X or zone Ydepending on the type of TW (in accordance with Sections 5.5 or 5.6).

8) Proximity calculations and projections are to be performed on each survey.9) Mud returns, will be monitored regularly for the presence of cement or gas.10) A ditch magnet will be installed on the flowline and monitored regularly for abnormal

presence of metal tailings.11) Wherever practicable, the annuli on TW's will be pressured up and monitored

regularly for sudden changes in pressure.12) The drilling operation will proceed at a controlled ROP to reduce the potential for

damage should a collision occur.13) The drilling operation will proceed with due caution and particular attention being paid

to sudden changes in ROP, drilling torque or other irregularities.14) The Contractor Directional Operator will be present on the drill floor at all times to

monitor drilling parameters.15) Unless required for directional control, the use of drilling motors will be avoided while

drilling in this situation. If motor use is unavoidable then a low torque motor will be thepreferred option.

16) Whenever possible use PDC bits instead of tricone bits.17) The DS will ensure that the most experienced personnel will be assigned for the tasks

outlined above (as recommended by the Contractor Directional Supervisor). The DSwill be notified immediately when any indications of collision are suspected orobserved.

18) A stock of at least 70 m3 of drilling mud should be available for emergency filling up.19) Well control drills will be intensified.




Figure 5.D- Anti-Collision Responsibilities (when there is Interference Between ExistingCompleted/Productive Wells and New Wells)




Figure 5.E - Anti-Collision Responsibilities (when there is Interference Between Existing NonCompleted/Plugged & Abandoned Wells and New Wells)




Figure 5.F - Anti-Collision during Well Suspension




5.9. EXAMPLE PROXIMITY CALCULATIONIn this example only two wells are considered (In multiple-well situations the procedure willbe identical).The target well (TW) is Agostino 17. The current well (CW) is Agostino 29.In the following table are the reported calculation inputs and outputs for a typical reportform. Figure 5.7 - Well Proximity Evaluation (AGOSTINO 29 - AGOSTINO 17) is thegraphical representation of the example.

Column Heading Description1 VD Vertical Depth of CW (m)2 MD Measured Depth of CW (m)3 Hole Diameter Hole diameter of CW (ins)4 Inclination Angle Inclination Angle of CW at that depth (deg.)5 Survey Type Tool MWD, etc.6 Horizontal Uncertainty Factor UF due to the survey tool and hole inclination for

the CW (m/1,000m)7 Radius of Uncertainty CWROU (m)= [Col 2 x Col 5]/1,0008 MD Measured Depth of TW (m)9 Hole Diameter Hole diameter of TW (ins)

10 Inclination Angle Inclination Angle of TW at that depth (deg.)11 Survey Type Tool MWD, etc.12 Horizontal Uncertainty Factor Horizontal Uncertainty Factor, due to the survey

tool and the hole inclination , for the TW(m/1,000m)

13 Radius of Uncertainty TWROU (m)= [Col 8 x Col 12]/1,00014 Curve A Threshold of separation (m)= [Col 7 + Col 13]15 Curve B Threshold of alert (m)= [Col 14 x Col 18]16 Curve C Threshold of danger (m) = [Col 14) x Col 19]17 Uncertainty Area Ratio UAR (See notes to )18 Coef. B Coef. of the threshold of alert (See notes to figure

5.a)19 Coef. C Coef. of the threshold of danger (See notes to

figure 5.a)20 Curve B using Coef. B21 Curve C using Coef. C22 Well Distance Separation (m) against depth

Note At 2800m TVD of the CW, the separation is 116 m, that is less than thethreshold of danger ,134.3m. At 2,900m TVD of CW the separation is106m, that is less than the threshold of alert, 107.6m.

Table 5.C - Proximity Calculation




Figure 5.7 - Well Proximity Evaluation (AGOSTINO 29 - AGOSTINO 17)




6. RECORD KEEPING6.1. OBJECTIVES

All well surveys will be filed in both printed and in electronic forms as specified in Section3.4.1. Electronic data must be produced on floppy disks (two copies) formatted according toEni-Agip Division and Affiliates specification. Write protected form are suggested.The reporting documentation for each well must include the standard feed back Eni-AgipDivision and Affiliates forms and the Final Report of the Directional Contractor.

6.2. DEFINITIONS6.2.1. Working Surveys

Working surveys are obtained during drilling operations from surveying tools utilised. Therewill also be intermediate surveys taken at casing point for the purpose of providing moreaccurate tie-in points for the following phase of drilling. A permanent record of all workingsurveys will be retained by both Directional Contractor and Eni-Agip Division and Affiliates.This is primarily for an accuracy check of survey instruments over the longer term.

6.2.2. Definitive SurveysIs the definitive or final survey will be obtained from the most accurate survey tool run in thehole section or from TD to mudline. Several surveys tied together (concatenated) may berequired to provide the definitive survey of the well (e.g. from surface to 133/8" casing shoe -Ferranti FINDS; 133/8" shoe till TD -NSG). The word ‘Definitive’ will not appear in any surveyreport other than the final concatenated definitive survey as defined by the SDE.

6.2.3. Final ReportIs the Directional Contractor generated report, relating to the directional and surveying ofthe well, supplied after the completion of the work. The contents are detailed in Section 6.5.

6.3. REPORTING RESPONSIBILITIESThe SDE will be responsible for the correct archival and retention of survey files and FinalReports.The D&CM and the Drilling Superintendent will be responsible for distribution and filling ofEni-Agip Division and Affiliates standard feed back forms according to the instructionsattached to each form.The Contractor Directional Supervisor will check and approve the Final Report, as detailedin Section 6.6, before releasing the final copies to Eni-Agip Division and Affiliates. (Refer toSections 6.5 and 2.2.5)




6.4. SURVEY REPORTING FORMATStandard Eni-Agip Division and Affiliates reporting forms will be used to report all directionaland surveying jobs; these are:

Survey Calculation’s Output.ARPO FB 2 Malfunctions And Failures Of Contractor's Equipment, Unsatisfactory

Services, New Equipment Test Report. (Refer to Section 7.2.1)ARPO FB 1 Contractor Evaluation Form (Refer to Section 7.2.2)Regarding QC data, the Surveying Contractor's own audited QC format is acceptable.The computed survey results format of survey data will be agreed previously between Eni-Agip Division or Affiliates SDE and the Directional Contractor. The following informationmust be included:

• Date.• Well/slot number.• Tool type with serial number and/or ID number.• Reference Datum (seabed/rig floor).• RKB height.• Tie in survey (on the first page of the listing only).• Magnetic Declination and North Reference.

Additional Data as determined by the SDE or the surveying company which is pertinent tothe survey will be included. This section will also include the following data, if applicable:

• Comparison data when tandem survey tools have been used.• Foresight reference used for gyro alignment with indication of points used.• IN and OUT run data.• Rotational survey data (check-shots at the same depth).• BHA description (NMDC length and Stabiliser positioning).




6.5. DIRECTIONAL CONTRACTOR’S FINAL REPORTThe Final Report draft will be reviewed and approved by the SDE before the final copy ishanded over. The Final Report provided by the Directional Contractor will be of the standardformat as described below:

6.5.1. Title PageThe title page will include:

• Platform/Rig name.• Well Name.• RKB - Seabed Interval.• Wellhead - UTM, Local and Geographic Co-ordinates with system references.• Target - UTM, Local and Geographic Co-ordinates with system references.• Target TVD.• Target Tolerance.• Target Azimuth.• Magnetic Declination.• Start Date/Finish Date.• Casing/Hole Sizes and Depths.

6.6. SUMMARY OF OPERATION/SURVEY PROGRAMMEA general overview of the directional drilling and surveying activities will be made for eachphase of the well.

6.6.1. BHA Performance ReportThe BHA performance report will contain, the data necessary to analyse and improvedrilling performance on subsequent wells.The format will be agreed by SDE and Directional Contractor Representative.The Directional Contractor Engineer at the rigsite will be required to complete the requesteddata on the report.

6.6.2. Definitive Survey ListingThe Definitive Survey Listing should include:

• Survey tool type and depth used.• Uncertainty in the bottom hole location.• Reference co-ordinates of platform centre .• Reference co-ordinates of well drilled.• North Reference.




6.6.3. Summary PlotThe Summary Plot of the well may be A3 or A4 in size and should include:The well plan and the drilled well path(s) for the vertical and horizontal sections.The target(s) and casing points.Critical directional drilling sections,(e.g. formation deepening influencing the BHAperformance)

6.6.4. Directional Drilling AnalysisA thorough directional drilling analysis shall be made by the directional drillers on-site withthe following topics to be considered:

• Highlights.• Failure Report and Analysis.• Recommendations for drilling future wells.




7. DIRECTIONAL DRILLING/SURVEYING SERVICES PROCUREMENT7.1. PROCURING SERVICES & MATERIALS PROCEDURES

The procurement of services, equipment and materials for drilling operations must follow theprinciples and procedures set out by the relevant local regulation requirements and complywith the Eni-Agip Division And Affiliates policy ‘Operating Procedure for purchasing ofservices and materials’ issued by VAP.With regard to Directional Drilling and Surveying in general the following aspects can beoutlined.Once the target location and size has been accepted, the SDE (or the TEAP representativeassigned to the project) should estimate the surveying accuracy requirements or constraints(e.g. the position and uncertainty in location of adjacent wells, and the difficulties expectedin the drilling of the proposed well). (Refer to Sections 3.1 and Errore. L'origineriferimento non è stata trovata. )The SDE (or the TEAP representative assigned to the project) will prepare a PreliminaryWell Programme that will contain the following topics as a minimum:

• Pore pressure gradient, fracture gradient and overburden gradient evaluation.• Preliminary casing programme.• Preliminary directional profile.• Preliminary time analysis by phase.

The DS (or the Head Office representative nominated by ARPO, assigned to the project),on the basis of the Preliminary Well Programme, will prepare for the Directional Drilling andSurveying service, a list of relevant equipment and personnel, with due consideration givento logistic aspects and local market constraints. The D&CM (or the Project Manager, or the concerned ARPO Department, depending ontype of procurement and geographic unit autonomy) will compile for the Directional Drillingand Surveying service, the requisition to be sent to the concerned Contracts andPurchasing Department. He will have responsibility for enforcing Technical Specificationissued by ARPO/STAP in the tender request. A technical judgement for the bids presented must be formulated from the D&CM (or theconcerned ARPO Department). It will consist of the following steps:

• Primarily the D&CM (or the concerned ARPO Department) will evaluate each bidsubmitted to ensure that the service offered in the tender is that which isrequired.

• If the bid is congruent with the service tendered a Technical Evaluation must beprepared for the Department that issued the Technical Specification.

• The D&CM (or the concerned ARPO Department) will formulate the TechnicalJudgement of the bids considering the appropriate Technical Evaluations andenclosing some final recommendations based on a global evaluation ofoperations in this context.




7.2. CONTRACTOR EVALUATIONContractor evaluation is essential to:

• Ensure the improvement of services provided, hence Company standards.• Instigate in conjunction with the concerned departments, a Vendors Lists

revision.The D&CM is expected to be very diligent to ensuring the timely and correct filling in of thefollowing standard forms:

7.2.1. ARPO FB-1 Malfunction & Failure ReportMalfunctions and failures of Contractor's equipment, unsatisfactory services, newequipment test reports must be detailed in the form FB-1 (Refer to figure 7.a).The DS is responsible for the correct filling in of the document and for the first stage in itsdistribution. The D&CM will ensure dispatch as per the relevant flow diagram.The receipt of this document by the appropriate departments is essential to initiate technicalenquiries.

7.2.2. ARPO FB-2 Contractor Evaluation FormThe evaluation of contractor performance according to the contract commitments must bedetailed in the standard FB-2 form (Refer to figure 7.b)The Drilling Supervisor, the SDE and the Drilling Superintendent are responsible for filling inof the form.The D&CM is responsible for approving and dispatching the forms as per the relevant flowdiagram.STAP will have the responsibility for ensuring feed-back to QUAF on the Contract.




MALFUNCTION & FAILURE REPORT(FEED BACK REPORT 01)

Report Date: Well Name: Well Code:

General InformationContract No: Contract Type: Contractor:Service/Supply:

Drilling Completion

Workover Duration Dates of Failure: Distributed By:

RIG SITEDescription of Failure:

Drilling & Completions Company Man:Adopted or Suggested Solution(s):

Contractor Contingency Measures:

Contractor Representative:DISTRICT OR SUBSIDIARY NOTES:

Failure Classification Status Operations Manager:Technical NormalManagement/Organisation Extreme Time Lost:Safety/Quality Innovative

Adverse Estimated Cost of Failure:MILAN HEAD OFFICE NOTES:

Analysis Code:

Figure 7.A - Malfunction & Failure Report

District/Subsidiary




CONTRACTOR EVALUATION(FEED BACK REPORT 02)

Report Date: Well Name: Well Code:

General InformationContract No.: Contract Type: Contractor:Service/Supply: Distributed By:

R1 Technical RequirementsFB_01 REPORT REFERENCES

FB Report No.: Time Lost (Hr.Min): Economic Cost (£M):Category Evaluation Score (0-9)

Suitability of Equipment and MaterialsCompliance of Equipment and Materials to theContractAdequacy of PersonnelMeeting with Operational Programme RequirementsMeeting with Contract Operation TimingsEquipment Condition/Maintenance

R2 Management and Organisational RequirementsFB_01 REPORT REFERENCES


Availability of Equipment and MaterialsTechnical and Operational Support to OperationsCapability and Promptness to Operational Requests

R3 Safety and Quality Assurance RequirementsFB_01 REPORT REFERENCES


Meeting with the Contract Agreement DSSAvailability and Validity of Requested CertificatesMeeting with Contract Quality Assurance Terms

Event Support DocumentationType of

Document:Subject: Issued By: Date:

Notes:

Failure Status Operations Manager Drilling & Completions ManagerNormal Extreme Adverse Innovative

Figure 7.B - Contractor Evaluation

District/Subsidiary




Appendix A - ABBREVIATIONSBHA Bottom Hole AssemblyCCD Centre to Centre DistanceCW Current WellDLS Dog Leg SeverityD&CM Eni-Agip Division and Affiliates Local Drilling & Completion ManagerDOP Drop Off PointDOU Depth of UncertaintyDS Eni-Agip Division and Affiliates Local Drilling SuperintendentDSR Drilling and Completion Supervisor at rig siteDW Deviated WellEMS Electronic Magnetic MultishotEOC End Of CurvatureEU Ellipse of UncertaintyFINDS Ferranti Inertial Navigation SystemFR Foresight ReferenceGC Geodetic ConversionGCT Guidance Continuous ToolGMC Geomagnetic ConversionGMS Gyro MultishotGSS Gyro Single ShotHDT High Resolution DipmeterHS Horizontal Component of Drill String Magnetic FieldKOP Kick Off PointMD Measured DepthMI Magnetic InfluenceMMS Magnetic MultishotMSS Magnetic Single ShotMWD Measurement While DrillingNMDC Non Magnetic Drill CollarsNSG North Seeking GyroORP Origin Reference PointPWP Project Well PlotQC Quality ControlRef. ReferenceRKB Rotary Kelly BushingsROC Radius Of CurvatureROP Rate of PenetrationROU Radius of UncertaintySC Survey CalculationSD Separation DistanceSDE Eni-Agip Division and Affiliates Local Senior Drilling EngineerSR Separation Ratio.SRG Surface Reading GyroSSSV Sub Surface Safety ValveST Steering Tool




TD Total DepthTIP Tie In PointTVD True Vertical DepthTW Target WellUAR Uncertainty Area RatioUF Uncertainty FactorUTM Universal Transverse MercatorVW Vertical WellWP Well Planning




Appendix B - BIBLIOGRAPHYDocument: STAP NumberDrilling Procedures Manual STAP-P-1-M-6140Survey Company Quality Control Procedures

Documents

ENI - Directional Control & Surveying Procedures