D Y N A M I C L O A D I N G

THE AUTHOR WILL examine theimposed longitudinal dynamic loads ondeepwater landing strings due todrilling vessel response to ocean heave.By considering the drilling vessel andthe landing string as a combined vibra-tion system, the author will also provideproof that determining the natural fre-quency of the landing string alone is jus-tified for a wide range of expected waveperiods. Additionally, sensitivities tomud, friction and structural dampingeffects are considered. The analysisdetermines the added axial forceapplied to the landing string as a func-tion of vessel heave period for givenlanding/casing string geometric andmechanical constraints.

In a reasonable range of expected waveperiods (2-8 seconds), the results con-firm at least two resonant frequenciesfor free-end boundary conditions andnominally at least one resonant frequen-cy for fixed-end boundary conditions.Depending on the effects of damping,imposed loads on the landing string areshown to be as much as 5-10 times high-er than the calculated static stretch loadbased on Hooke’s Law at peak heaveamplitude. The importance of such anevaluation is discussed in light of thefact that landing long, heavy, large diam-eter casing strings from dynamicallypositioned drillships in deep water hasbecome quite common.

Evaluation of Heave Induced Dynam-ic Loading on Deepwater LandingStrings (IADC/SPE 87152) D Everage,S E Ellis, N Zheng, T H Hill Associ-ates Inc.

W E L L B O R E E N L A R G E M E N T

The success of deepwater explorationand development operations is greatlydependent on utilizing larger OD casingto reach the ever-increasing depths oftoday’s prospects. An operator utilizednew hole enlargement technology tosimultaneously drill and enlarge a well-bore to facilitate the installation of amultiple string casing program in thedeepwater Gulf of Mexico.

The authors will present a case studydetailing how proper planning and theutilization of new hole enlargement

technology matched with a rotary steer-able system culminated in the success-ful execution of this critical well con-struction operation. As part of the plan-ning process, hydraulics analyses andBHA stabilization optimizations usingspecial computer software will be dis-cussed. Also to be presented is theapplication of a new design concentricreamer in a deepwater tight clearancecasing program that enlarged more than18,000 ft of four different sized wellbore.

Wellbore Enlargement for a Deepwa-ter Casing Program: Case Study andDevelopments (IADC/SPE 87153) D FCourville, R D Childers, Smith Inter-national Inc.

W E L L D E S I G N

A major exploratory campaign is beingcarried out off the southeast cost ofBrazil. More than 150 wells will bedrilled during the next two years inwater depths from 3,280 to 9,200 ft.

These deepwater exploratory wellswere designed taking into account safe-ty, well data reliability and well cost.Various innovations were implementedincluding a new casing design thatreduced the number of casing sectionsfrom five to three, a new improved deep-water wellhead system and an opti-mized drilling fluid system.

The innovative approach adopted todrill the wells significantly reduced thetotal drilling time, which was important

due to the shortage of deepwaterdrilling vessels in the current market. Afield case reporting a well construction,including design and complete opera-tions from spud to TD will be presented.

Innovative Design for DeepwaterExploratory Wells (IADC/SPE 87154) JC Cunha, Y Irokawa, Petrobras.

T E S T I N G B O P S

Pressure testing BOPs with syntheticbased mud (SBM) requires additionaltesting time as a result of PVT influ-ences associated with SBM. They areespecially pronounced in deepwater andhigh pressure test environments.

The project was motivated by an effortto minimize the waiting time at the rigduring a BOP test. The primary objec-tive was to demonstrate that the pres-sure decline signature of the fluid isquantified by the fluid PVT behavior,mechanical influences and thermody-namic behavior during pressurizationand subsequent cool down. The secondkey objective was to demonstrate thatthe pressure decline resulting from aleak is detectable.

The authors will present salient aspectsof the data acquisition, the data inter-pretation, and the modeling techniques.

Advanced Analysis Identifies GreaterEfficiency for Testing BOPs in Deep-water (IADC/SPE 87155) C Franklin, ML Payne, BP; U B Sathuvalli, BladeEnergy Partners; R Vargo, Hallibur-ton Energy Services.

B O P C O N T R O L

Industry standards (API and MSS)require ram BOPs to close within 30 sec-onds and annular BOPs within 45 sec-onds. Subsea BOP response times asso-ciated with all-hydraulic piloted controlsystems are controlled by a number offactors, but the hydraulic pulse time topressure up and bleed off the 3/16-in. IDpilot lines to shift the subsea control podpilot valves is very hose-length depend-ent. Thus, the pulse time to shift the podpilot valves is fairly constant regardlessof the water depth, given that the umbil-ical length remains constant.

A newly patented electro-hydraulic (EH)control system has been developed that

46 D R I L L I N G C O N T R A C T O R January/February 2004

Deepwater solutions to be presented at conference

Hydraulic Subsea Connections

Electrical Subsea Connections

Pressure Compensated Electrical Chamber

Solenoid Assembly

A newly patented electro-hydraulic (EH) controlsystem has been developed that can be retro-fitted to existing installed all-hydraulic subseacontrol systems, utilizing the existing driller’sand toolpusher’s panels, pump/accumulatorunit, UPS, most of the rig’s wiring and both sub-sea pods. IADC/SPE 87156

can be retrofitted to existing installedall-hydraulic subsea control systems,utilizing the existing driller’s and tool-pusher’s panels, pump/accumulatorunit, UPS, most of the rig’s wiring andboth subsea pods. The EH concept cen-ters around running electrical lines tocritical solenoid functions (rams, annu-lars and connector releases) andhydraulic lines to all other non-criticalfunctions. A module consisting primari-ly of solenoids and hydraulic/electricalconnectors is packaged to fit on top ofthe existing all-hydraulic control pod.The overall “kit” has been designed tobe placed aboard the rig and BOP stackduring a long rig moves thus not requir-ing any shipyard time.

Fast Response Retrofittable Ultra-Deepwater BOP Control System(IADC/SPE 87156) M A Childers, J Cur-tiss, Atwood Oceanics; M M Buckley,Cameron Drilling Systems.

R I S K A N A L Y S I S

Many of the latest generation of ultra-deepwater rigs included emergencyBOP control capabilities, sometimesreferred to as secondary interventionsystems. Such systems represent thelast line of defense in containing a well.Building on installations that have beenin service for many years, these capabil-ities range in functionality and purposefrom providing an alternate means tooperate BOP functions in the event oftotal loss of the primary control systemto assisting personnel during incidentsof imminent equipment failure or wellcontrol problems. They can be actuatedautomatically or manually. They can uti-lize components of the primary BOPcontrol system or be totally independ-ent. With as many permutations asthere were rigs built, an understandingof the capabilities and limitations thatexist on a particular rig is of criticalimportance in assessing the risks asso-ciated with a drilling program.

While there currently are no standardterms in use to describe the essentialattributes of systems, the author willrecommend definitions and terms for acommon understanding. The definedterminology will be used to compare andcontrast system parameters, identifyingvarious system strengths and weak-nesses for use in risk analyses.

Risk Analysis of Emergency BOP Con-

trol Systems to Ensure DesiredResults (IADC/SPE 87157) J P Sattler,WEST Engineering Services Inc.

T A U T - L E G M O O R I N G

As exploration moves into greater waterdepths, the use of traditional catenarymooring systems requiring long andheavy mooring lines becomes too costly.As a result the offshore industry hasadopted the taut leg mooring system asthe best alternative. The essence of thesystem is a smaller footprint, lightweight mooring lines and anchoringpoints that withstand both horizontaland vertical loads. This technology isbased on the use of synthetic mooringropes and drag embedded verticallyloaded anchors (VLA’s). The choice for ataut leg mooring system in deep water,including VLA’s and polyester rope,results in a more economic solution.

Since 1998 some 60 Stevmanta VLA’shave been installed in water depthsexceeding 1,000 m primarily for perma-nent moorings. The new VLA anchorsallow the use of drag embedment typeanchors for use with taut leg moorings.The anchors are very light, easy to han-dle, install and recover.

The author will discuss the latest on theuse of drag embedded VLA anchors, fortemporary mooring systems in deep toultra-deepwater locations. Discussionwill include the economics of dragembedded VLA’s versus suction piles;taut leg mooring system principles; his-tory of taut-leg mooring; installation andretrieval of VLAs; safety factors;improvements to accommodate rigmoorings; and a case study.

Taut Leg Moorings Using Polyesterand VL Anchors (IADC/SPE 87158 –Alternate) T Adnevall, Moorwest Inc.

D R I F T O F F A N A L Y S I S

In support of the Gnarlyknots-1 welldrilled by the Glomar Jack Ryan dynam-ically positioned drillship in 4,308 ft ofwater in early 2003, drift-off riser analy-sis was carried out to establish watchcircles for the emergency disconnectsequence (EDS).

Drift-off analysis of the vessel and risersystem is a key element to the success-ful management of the riser on a dynam-ically positioned drillship, as it dealswith protecting the equipment in case of

the potential loss of vessel power.

At this well site, high sea states com-bined with wind and current conditionsdictate that drilling should be carriedout in accordance with well-specificoperating criteria. During the planningphase, extensive discussion was heldbetween the operator and the drillingcontractor to establish well-specificoperating criteria. Riser analysis of thedrift-off scenarios was used to establishthese criteria in an effort to avoid poten-tially exceeding allowable limits in theriser and conductor pipe. As the drillingprogressed, the well-specific operatingcriteria were applied to actual metoceanconditions being encountered. Theauthors will describe the drift-off analy-sis carried out for this well and how itwas applied to facilitate the drillingoperations.

Drift-Off Analysis to SupportEDS/Riser Management in DeepWater in the Great Australian Bight(IADC/SPE 87160 – Alternate) J NBrekke, D Moorthy, M A Wishahy,GlobalSantaFe; E O’Sullivan, MCSInternational.

C E M E N T I N G

As an alternative to standard energizedfluids, special cementing systems basedon packing volume fraction and ratios ofsized particles have been used with suc-cess in water depths exceeding 6,000 ftin the Gulf of Mexico. The author willprovide case histories and discuss theuse of these systems for a wide range ofdeepwater situations. The systems arespecially designed to provide optimizedgel and compressive-strength develop-ment in low temperature environmentswhile allowing the thickening time to betailored to any wellbore geometry.

Slurry volumes from 1,500 to 2,500 bblhave been pumped without incident.Their intrinsically low permeability andporosity at both the slurry and setcement stages provide resistance toexternal attacks and influx of water orgas. In addition, these systems are test-ed and pumped using standard equip-ment. Extra personnel are not required.

Cementing Deepwater, Low Tempera-ture Gulf of Mexico Formations Proneto Shallow Flows (IADC/SPE 87161 –Alternate) P Rubinstein, R F Keese,Schlumberger; J O’Leary, BP. �

January/February 2004 D R I L L I N G C O N T R A C T O R 47