Feasibilty Radial Drilling Revised

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OIL AND NATURAL GAS CORPORATION LIMITEDINSTITUTE OF DRILLING TECHNOLOGY

KAULAGARH ROAD, DEHRADUNFAX – 0135 – 758926.

File No. IDT.DRDTG / OVL / 2012-13 / 1 Dated 13.06.2013

From: - ED,HOI-IDT

To: - GM(D)-Head Drilling, ONGC Videsh ltd

Subject: Feasibility of carrying out Radial drilling at imperial energy

This is in reference to the letter dated 22.05.13 from GM(D), OVLregarding carrying out of 'Radial Drilling' at Imperial Energy Projects in

Russia to enhance production, on trial basis. It has been desired to havethe opinion of IDT on trying out this technology in the above mentionedfields.Regarding the use of this technology, a presentation was made by Indianrepresentative of M/s Radial Drilling Services on 27.05.2013 at IDT. Aftergoing through the presentation and examining the data available on the netregarding claims made by various vendors of this technology like Buckman

jet drilling, Jet drilling WS, eSteams, Jereh ESC, ZRL, it is opined that Jetdrilling/radial drilling is being effectively used to capture the benefits of

horizontal drilling in smaller-scale reservoirs. It has been proven toenhance production rates, reduce decline rates, reduce near wellboredamage and recover more resources from mature wells, Also thistechnology can be used for deep acidization, Directional water injection to

reduce injecting pressure and enhance impact, CO2 injection in placeof SAGD in thick oil reservoir etc.. It involves drilling 1’’ to 2’’ lateral hole extending upto 300ft in length.However some company like JET drill refutes such claim and give realisticaverage length of lateral as 60 to 160ft only.The number of such radialholes is normally 3-4 from a particular depth after cutting holes in the

casing using the same set of equipments.

The stability and straightness depend on formation characteristic likehomogeneity and in situ stresses level. Currently no technology iscommercially available to map or track the progress and placement of theRadials being drilled. A lateral can turn left -right or up -down after drilling a



loose/soft lump of formation.Also when a natural fracture is encountered ,further drilling is not possible. Other constraint or limitations are:

Existing Perforations:No comments from any vendor as to what effectthey will have on success of casing milling

Casing size. Currently available radial drilling equipment can operate inproduction casing sizes of 5½ in. OD or greater. The equipment can also operate in 4½-in. or greater in-gaugeopen hole.

Casing grade. The tungsten carbide bits used to mill casing exits are limited tocasing grades of N-80Sand abrasion cutting limit not known

(Russian grade D) or less.

Casing wall thickness. The maximum casing wall thickness that theavailable casin cutters can mill is

Casing cementation. In order to successfully initiate a casing exit, radialdrilling equipment requires a good cement bond between the casing and theformation. A poor casing bond generally results in difficulty or failure in jetting

operations. The competence of the cement bond is generally assessed by cement bond logging.

Wellbore inclination. Since the radial drilling system discussed here reliesupon gravity to seat the radial drilling assembly in the deflector shoe, the well inclination should not exceed60° from vertical.

Wellbore depth. Currently available systems are designed to operate at amaximum depth of 3,000 m-3500m..

Porosity Min 3-4%

Wellbore rathole. A rathole of at least 10 m (33 ft) is required to allow theetted debris to settle beneath

the deflector shoe.

Bottomhole conditions. Operating temperatures at reservoir depthshouldn’t exceed 120°C (250°F).Bottomhole pressure should not exceed6,500 psi.



As such, the limitations associated with radial drilling technology are mainlyno control over direction, managing production in case of undesirablezone entry, no possibility of intervention etc.

Oprerational sequences can be generally summarized as

WORK OVER RIG RJD UNIT & Accessories1 Kill Well2 Remove X-Mas & Install BOP

3 POOH Prd String, Packer4 Clean hole, Scraper and bit trip5 RIH Deflector tool on tubing

6

3

t o

5

d a y s

RIH gyro tool on wire line,engage with DeflectorUBHO

7 Ascertain Direction, rotate tubingto orient D-tool in desireddirection

8 POOH Gyro ???9 RIH casing cutter, Cut hole in

csg, pull cutter inside D/tool androtate to next hole direction?? Oragain gyro run required

10 POOH cutter . RIH jetting toolJet dn laterals.POOH. CT, andtubibg with D/tool. R/DN CT unitetc.

11 RIH tubing w/completion assemblyRemove BOP, install X-mas,SetPacker etc

12 Swabbing the well required to fullyactivate flow through radials

13 WELL CONTROL: TUBING –

CASING ANNULUS- RIGRESPOSIBILTY-contingency planif Lubricator on CT fails

Ct –TUBING , Responsibility

RJD



It is beyond the purview of IDT to comment on enhancement of productionthrough such radially drilled laterals as it invoolves complex reservoirmechanics and production technology alternatives and overall economics.However, most of the vendors have claimed substantial gain in productionthrough implementation of this technology in mature fields. As perliterature survey, it appears that this technology is best suited for matureand depleted fields and most effective when vertical permeability is much

higher than horizontal one.

It is understood that Radial drilling is going to be implemented in India in 4wells of Gujarat of M/s SELAN in August/September 2013 and is expectedto be completed in appox 1 month time. Therefore it is suggested thatresults of same can be compared with G & G data of imperial wells ofbefore taking a decision regarding implementation of radial Drilling inRussia.







Applications of Radial Drilling

Technology Radtech

• Reverse declining production rates.

• Improve and extend drainage area in

productive formations. • Reach beyond the damaged area of the Well

Bore.

• Improve the drainage.

• Produce heterogenous formations. • Improve water injection.

• Improve vertical cleaning.

• Reduce water coning.



Regards,

( K Krishna Pratap)) ED-HOI-IDT

Well Selection Criteria

Required technical information for a proper well selection:

– Electric logs CBL – VDL – CCL – GR

– Rock mechanics

– DST and RFT results if available

– Well spacing

– Depth of interest ( producing formation) –Thickness of the producing formation

– Mechanical integrity of casing

– W/O and O/G contacts

– Historical production data of oil, gas and water – Previous optimization data (if any) – Porosity and permeability data of the producing formation

– Hole deviation/inclination

– Type and weight of drilling fluid used

– BHT/BHP

Documents

Feasibilty Radial Drilling Revised