Reliance inIndia—The Powerof Innovation

In October 2002, Reliance Industries, India’s largest

private-sector company, and its partner, Canadian

independent Niko Resources, announced a world-

class, giant, deepwater gas discovery 20 km offshore

in the Krishna Godavari basin on block KG-DWN-98/3.

This discovery is the biggest gas find for India in three

decades, and was the world’s largest gas discovery in

2002. In this article, Kamlesh Raj Saxena examines the

significance of this major gas find and the technology

that made it possible.

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Exploration—choosing the best technology In 2001, Reliance began its firstcampaign as operator in the hostiledeepwater environment off the eastcoast of India. Faced with a complexprocess in which information wouldhave to be shared between largenumbers of people, Reliancedeveloped an operational commandcenter where key decisions aboutfield development could be madequickly and efficiently (Figure 4).

The company faced the challenge of acquiring log data in a field whereno wells had been drilled before. Themain objectives were safe drilling andaccurate formation evaluation. Toachieve this, Reliance had to selectthe most appropriate logging tools.Without previous wells to refer to, it was impossible to predict how themud system, the sands, and the claywould behave, and what sort ofreservoir the company would bedealing with. There was a possibilitythat the hole would not be sufficientlystable for logging, and also uncertaintyabout the combination of tools thatwould be required for advancedformation evaluation. Reliance decidedto deploy logging while drilling (LWD)and Schlumberger wireline services in order to achieve its formation-evaluation objectives.

Reliance’s first exploratory well was drilled in a deepwater block; alleight wells drilled in this block haveproved successful. This 100 % successrate has been achieved through acombination of careful planning, acommitment to superior technology,and the presence of technicalinnovators on the Reliance staff.

State-of-the-art technologies fromSchlumberger Wireline, and Drillingand Measurements have helpedReliance to increase drillingefficiency, obtain a comprehensivesuite of well data, and improveunderstanding of the wells and thereservoir. Following the success ofReliance’s exploration operations,some of these tools and techniquesare now being applied by severalother Indian exploration companies.

Figure 5: LWD helps engineers to locate key target layers at the earliest opportunity and deliverssignificant rig-time savings.

Figure 4: Reliance has developed a real-time command center to control field operations.

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Over the last decade, the Indian oil industry has applied the latest

technology to development andproduction in the country’s key fields.This shift toward high technology has been accelerated in recent years by India’s leading exploration andproduction (E&P) companies. RelianceIndustries Ltd, the largest private-sectorcompany in India, started its own oil andgas exploration operations in 2001 andhas rapidly become a major participantin the E&P arena (Figure 1).

Gas for growthIn October 2002, Reliance’s Oil andGas Division announced the keydiscovery of a supergiant gas field in the D6 block off the east coast of India. The discovery of a massive,deepwater natural gas field a shortdistance from the eastern coast ofIndia is of great significance, as Indiais currently striving to boost oil andgas production to meet the risingenergy demands of its fast-growingeconomy. This field is the first majorhydrocarbon accumulation to be foundby an Indian private-sector company.

The discovery is located 20 kmoffshore in the Krishna Godavari basinon block KG-DWN-98/3 (Figure 2). Itis the biggest gas find in India in threedecades, and was the world’s largestgas discovery of 2002. The gas-bearing structure lies in an averagewater depth of 900 m and is 1,850 to2,200 m subsea. Results from 3Dseismic surveying and a recent four-well drilling program indicated ananomaly of about 177 km2 and ahydrocarbon column 342-m thick,which confirmed that this is one ofthe largest gas discoveries ever madeoffshore India.

The discovery well was drilled to atotal depth of 2,900 m in May 2002, and95⁄8-in casing was set to approximately2,200 m. A second well was spudded inJune by the Transocean Discoverer

534 drillship in 1340 m of water.Reliance estimates the gas in place to be 408 × 109m3/d. However,integrated 3D seismic and wellinterpretations indicate that thereserves could be higher. Reliancehopes for daily production of up to40.8 × 106m3/d.

Cased-hole tests were conducted ontwo wells and resulted in equipment-constrained flow rates of 1.1 × 106 and0.8 × 106m3/d, but individual welldeliverability is expected to exceed28 × 106m3/d.

Between 1980 and 2001, India’senergy consumption rose by more than200 %. This rapid increase was duemainly to the country’s increasingpopulation and rapid urbanization. In2001, coal accounted for almost 51 % of India’s energy consumption, withmost of it being used in the powergeneration sector; petroleum made up34.4 %; while natural gas (6.5 %) andhydroelectricity (6.3 %) accounted formuch of the remainder (Figure 3).Natural gas, however, is growing inimportance, its share of consumptionhaving risen from a mere 1.4 % in 1980.In India, new energy sources are beingintroduced at the expense of coal, andthe Reliance gas discovery will have adirect influence on this process.

Figure 2: Reliance’s major gas discovery islocated in the Krishna basin.

Figure 1: Reliance Industries Ltd is the largest private-sector company in India.

Figure 3: In 2001, India’s energy consumptionwas dominated by coal. The development of thegiant gas fields is expected to shift the balance.Source: Energy Information Administration,United States Department of Energy.

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Analysis of thin-bed formationsOne of the biggest challenges indeveloping deepwater reservoirs isevaluation and reserves estimation inthin-bed pay zones. Resistivity resultsfrom the arcVISION tool (Figure 7)were combined with HRLA* High-Resolution Laterolog Array resistivitydata to provide estimates of resistivityanisotropy and net pay.

LWD logs from the first wellindicated the presence of thin beds andmassive sands. Using the informationacquired during LWD, the wirelinelogging runs were optimized to save rig time, as well as to obtain maximuminformation and data. However, as thevertical resolution of the LWD logs wasinadequate for thin-bed evaluation, itwas decided to acquire HRLA–AIT*Array Induction Imager Tool resistivitylogs in combination with PlatformExpress* integrated wireline logs (in high-resolution mode). Thisenabled the geology and geophysicsteam to perform advanced thin-bedformation evaluation by determiningthe vertical and horizontal resistivities,and the resistivity anisotropy caused by the intersected, thinly laminatedformations.

The results had a dramatic impacton the gas reserves estimate, as theyindicated a 700 % cumulative increasein gas (Figure 8). Moreover, thecombination of HRLA and AIT loggingin the first run provided confidence in

Figure 7: Thin-bed pay zones present a seriouschallenge in many deepwater developments.Resistivity measurements help engineers toestimate net pay and choose appropriate drillingstrategies.

Fast, efficient drilling LWD logs help reservoir engineers tolocate key target layers during drillingand select the correct combination ofwireline evaluation tools for detailedwell analysis (Figure 5). By reducingtotal logging time, LWD operations alsoprovide significant rig-time savings. Inextreme conditions, for example,where a well cannot be logged withwireline tools or if the hole is lost, LWDlogs may prove invaluable (Figure 6).

Offshore India, Reliance has useddrilling performance measurementsfrom measurement-while-drilling(MWD) tools to enhance drillingperformance and safety. These drillingmeasurements have helped thedrilling engineers to take correctiveaction while drilling. The use of a real-time caliper has revealed hole shapeand condition, and thus made it easierfor the company to evaluateformations and make appropriatecompletion decisions.

During the process of formationevaluation, the quadrant densitycurves (upper, bottom, left, and right)were obtained using an arcVISION*Array Resistivity Compensated tool.These curves, and other wirelineinformation, helped to improve logevaluation for Reliance in bad holeconditions. In good hole sections, allfour curves matched the wirelinedensity curve, but in bad hole sectionsthe bottom density (ROBB) was thehighest reading.

Deepwater reservoirsAround the world, most of the oil and gas exploration is taking place infrontier deepwater areas. As drillingreaches new depths and wells arerequired to deliver consistently highrates of production, the challenges foroperators are becoming increasinglycomplex. Operators need to findservice partners that providetechnological innovation with globalmanagement expertise: thiscombination of skills helps to bringfields on-stream faster and ensurehigh levels of recovery.

Reliance has used a range of LWDand MWD services in India; full suitesof LWD triple-combo logs in verticalwells for enhanced formationevaluation; density images and LWD

caliper data for formation evaluation;high temperature (>150 degC)LWD/MWD measurements in realtime: and APWD* Annular PressureWhile Drilling measurements in deepand shallow waters to increase drillingefficiency. Reliance was the first oilcompany in the region to apply theSADN* Stabilized Azimuthal DensityNeutron tool in a 12-in vertical hole.

Drilling-fluid planning, holecleaning, and drilling mechanics wereoptimized using real-time leakofftesting; real-time-equivalent staticdensity data; and real-time collar

rotation-speed, shock, and slipmeasurements respectively.

Reliance also utilized real-time logtransmission of LWD data from thewellsite to headquarters using aVSAT–InterACT* real-time monitoringand data delivery system. This systemenabled the company to utilize expertanalysis away from the wellsite andrespond rapidly to deal with potentialproblems or to change well plans tomeet changing conditions, thus savingtime and money.

Figure 6: In situations where wells might be lost or impossible to log with wireline tools, LWD toolsprovide invaluable data.

Figure 8: Careful analysis of resistivityanisotropy boosted estimated gas reservesby an astounding 700 %.

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Figure 11: The slowness-time-coherence method enables analysts to determine compressional, shear, and Stoneley slowness values. The results yieldvital information for formation evaluation and other seismic applications.

the mud system.High-resolution borehole image

logs acquired by the FMI* FullboreFormation MicroImager and theOBMI* Oil-Base MicroImager incombination with the DSI* DipoleShear Sonic Imager indicated thepresence and the size of the thin beds(Figure 9). The image log helped toprovide a realistic estimate of net pay.The sand count method was also usedto estimate the net-to-gross ratio inturbidite sequences.

For the first time in India,Schlumberger has performed sandinganalysis using the DSI cross-dipolemode and calculated the criticaldrawdown pressure at which sandwould be produced. This sandingprediction was found to agree withthe test results to within 34 kPa. Inunconsolidated sands, Reliance usedStoneley wave characteristics forcontinuous evaluation of mobility,with the results being calibrated toMDT* Modular Formation DynamicsTester mobility data.

Nuclear magnetic resonance (NMR)measurements were used to their fullpotential to give high-resolutionquantitative permeability and porositymeasurements. In another Indian first,the CMR-Plus* CMR high-speed loggingtool was used, in enhanced precisionmode (EPM), for thin-bed evaluation to

estimate high-resolution permeabilityand capillary pressure curves, whichwere then used as inputs in reservoirsimulation (Figure 10). The success of this method depends on goodcalibration with core samples.

Integration of DSI, vertical seismicprofile (VSP), and surface seismic data was used to assess the wellborestability, the pore pressure, and thefracture gradient prediction ahead ofthe bit. The geomechanical propertiespredicted for the next drilling sectionwere a very close match to the actualdrilling results.

The MDT tool has proved extremelyvaluable for Reliance. The companyused the tool with a dual packer torecord pressure test data in 95⁄8-incasing in a gas reservoir to obtainrepresentative formation pressures at separate depths during the fieldexploration program. This is the firsttime that this technique has beenapplied in India. The LFA* Live Fluid Analyzer for MDT tool was run in combination to acquire arepresentative water sample, and thepumpout module was used to induce a sufficient drawdown in the formationto obtain a quantitative estimation ofpermeability and skin factor.

Three-component processing ofzero-offset VSP data

Figure 9: The OBMI tool helped to identify thin beds in the reservoir sequence.

A zero-offset VSP (ZVSP) survey was

Figure 10 The enhanced precision mode of theCMR-Plus high-speed logging tool gives excellentrepeatability and provides excellent thin-bedevaluation results.

acquired in a deviated well using theCSI* Combinable Seismic Imager tool.Visual inspection of the X and Ycomponents clearly showed goodmode conversion, so a decision wastaken to carry out three-componentprocessing of the ZVSP data utilizingthe DSI data. The objectives were toestimate shear slowness from theZVSP and compare this value with theshear slowness obtained from the DSItool data; validate the shallow zoneshear where DSI shear was notpresent; predict shear below totaldepth; and generate a P-S corridorstack and a synthetic seismogram.

The rig source VSP survey wasacquired at 7.5-m sampling intervalsusing a four-level VSI* Versatile SeismicImager tool. The 7.5-m sampling,coupled with the VSI tool, deliveredexcellent VSP data for all threecomponents (Figures 11 and 12). Themaximum frequency that could berecovered from the data was 120 Hz at reservoir level (2000 m).

Extreme conditions, extremetechnologyIn the harsh, high-pressure, high-temperature deepwater conditions offIndia’s east coast, drilling and logging

Figure 12: The VSI sensor package provides acoustic isolation and noise suppression, thusdelivering excellent VSP data for all three components.

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Figure 13: The OBMI tool provided formationevaluation in high-pressure, high-temperaturewells with oil-base mud and helped Relianceto identify thin beds (top) and fracturedbasement (bottom).

operations severely test oilfield toolsand technology. Reliance’s explorationplans required the deployment ofXtreme* high-pressure, high-temperature logging tools forformulation evaluation. In Xtremetools, various technologies areintegrated in one wireline string forlogging under extreme conditions.Rugged, reliable sensors deliver high-quality, accurate formation evaluationdata and precise assessments of netpay. The Xtreme platform’s fivedepths of investigation and threevertical-resolution measurementsoffer the same high-quality results asthose recorded with the conventionalAIT family. The logging operation wasa complete success and markedanother oilfield first in India.

When Reliance switched to an oil-base mud system to achieve betterdrilling results at depth, it becameessential to evaluate the complexformation using high-resolution logs,so Reliance used the OBMI tool. TheOBMI tool was run successfully over1,970 m, the longest interval everlogged by this tool, at temperaturesapproaching its operational limits.These logs were used to identify thin beds and fractured basement, see Figure 13.

Wireline servicesIn terms of wireline services in India,Reliance was the first company to usea Platform Express–AIT–HRLA toolcombination for thin-bed formationevaluation and reserves estimation

in deepwater reservoirs, and to applythe Sharplite–ELANPlus* advancedmultimineral method for thin-bedpetrophysical evaluation of sharpenedlogs with FMI vertical resolution. Thecompany has also introduced theAPS* Accelerator Porosity Sonde toolto improve neutron measurement inshaly/silty deepwater reservoirs(Figure 14).

Having established that thereservoir sequence was dominated bythin pay sands, Reliance performed adetailed evaluation of the beds usingthe CMR-Plus tool in EPM mode toprovide enhanced data precision.EPM data acquisition improves thesignal-to-noise ratio for short T2components and, therefore, theprecision of the total- and bound-fluidporosity values. A typical EPMsequence consists of a long wait-timesequence followed by several repeatsof a short wait-time sequence.

The futureThe Reliance gas discovery has far-reaching implications for India’shydrocarbon gas reserves andrequirements. A commitment totechnology and bold decision makinghave helped to elevate Reliance to amajor player in the Indian E&P sector.The use of advanced wireline andLWD technologies has contributed toReliance’s exploration success.Reliance is currently planning itsdevelopment campaign for the D6block and will build on past successesand move forward with the mostappropriate technology for thechallenges ahead.

Figure 14: The APS tool improves neutron measurements in deepwater reservoir sequencescomposed of interbedded shales and siltstones.