Project Oriented Dissertation

On

FACIES CHARACTERIZATION OF CLASTIC RESERVOIR OF LOWER GORU AND PARIWAR

FORMATIONS, JAISALMER BASIN ,RAJASTHAN, INDIA

At

KDMIPE,ONGC,DEHRADUN

Presented by:-SAMIUR RAHMAN KHANRoll No.-10479SCoo3

Introduction Cores obtained while drilling (using a core-barrel), by virtue of

their size and continuous nature, permit a thorough geological analysis over a chosen interval.

The area under study lies in northwest part of Jaisalmer Basin, Rajasthan

This project work pertains to the study of only Mesozoic section(Lower Cretaceous) in the subsurface as a number of hydrocarbon occurrences have been reported in the area especially in Pariwar and Goru formations.

ObjectiveThis study is applied to understand detailed information about the sedimentary rock type, mineralogy, texture, sedimentary structures and the variation of rock property of Lower Cretaceous Clastic section of Jaisalmer Basin ,Rajasthan.The data generated thus was taken to interpret the subsurface lithological variations, depositional environment and reservoir characteristics

Geological setting Rajasthan basin is a peripheral fore-land basin & it is a Category- I basin.

Rajasthan basin possesses three important basins viz.,

Jaisalmer, Bikaner-Nagaur and Barmer, stretching over

an area of about 1,20,000 sq. km. These basins are bound in the east and south-east by the Aravalli ranges and in the north-east by Delhi-Sargodha ridge. Towards the north and north-west it merges in to the Indus shelf. The western and south-western limits are marked by the Jacobabad High and Badin platform in Pakistan.

Jaisalmer basin is the westernmost is separated from the Bikaner- Nagaur basin by the Pokaran-Nachana high to the northwest and from the Barmer basin by the Barmer-Devikot- Nachana high in the south.

A pronounced NW-SE-trending regional

step-faulted Jaisalmer-Mari high zone,

marked by the Kanoi and Ramgarh faults

that traverse the centre of the basin and

divides it into the Shahgarh sub-basin, the

Miajalar sub-basin and the

Kishangarh sub-basin

Tectonics Zones Map of Western Rajasthan Basin (Source-www.dghindia.com)

Methodology adopted

1-Megascopic study2-Petrography or Thin section study 3-X-ray diffraction 4-Scanning Electron Microscopy

DETAILS OF CONVENTIONAL CORES

Details of sample for various studies Details of thin section DETAILS OF SAMPLE FOR X-RAY DIFFRACTION

DETAILS OF SAMPLE FOR SEM ANALYSIS

MEGASCOPIC STUDY OF CONVENTIONAL CORE-1(cc-1)Lower Goru Member Megascopically ,the core comprises dark grey ,hard and compact,

fine to medium grained, sub angular to sub-rounded , micaceous and calcareous sandstone , brachiopoda shell along with glauconite and dark color minerals .At some places it is showing flaser bedding.

showing reaction with HCL10%

Flaser bedding

Petrography of conventional core-1 Petrographically the sandstone consists of Quartz (60-75%),Glauconite

(10-20%) ,mica (up to 5%),opaque minerals like pyrite(less than 5%),feldspar (upto3%),ferruginous clayey matrix (up to 10%),and ferron calcite cement (up to5%).

Petrographically these sandstones are lithic arenites

X-Ray Diffraction analysis of conventional core-1 X-Ray Diffraction analysis of clay fraction of the core(Depth-1418.45m, 1426.40m) indicate the presence of kaolinite 78.25% , 79.42% and illite 21.75% -,20.58%.

SEM analysis of conventional core-1

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MEGASCOPIC STUDY OF CONVENTIONAL CORE-2(lower Goru Member)

Megascopically the core comprises dirty white to grey ,hard and compact ,very fine grained/ siltstone, sub-angular to sub rounded, calcareous sandstone with lot of dark minerals and micaceous with black to dark grey fissile shale. Sandstone showing small scale cross-lamination.

Petrography of cc-2(Lower Goru Member) Petrogarphic study indicates sandstone are moderately sorted sub-

angular to sub-rounded quartz (50-70%), mica (5-10%),rock fragments sideritic clay clasts (upto5%),clayey matrix up to 10%,ferron calcite cements( 5-10%),with traces of feldspar ,glauconite and opaque minerals along with authigenic kaolinite.

Petrographically these sandstone are quartz wacke.

XRD ANALYSIS OF CC-2 (BULK SAMPLE ANALYSIS) Lowre Goru Member

Bulk sample analysis by X-Ray Diffraction of the core(Depth-1514.47m) indicates dominance of quartz 73.7%, kaolinite 14.2% , siderite 7.1% , illite 4.2% and minor calcite.

X-Ray Diffraction analysis (clay fraction)

X-Ray Diffraction analysis of clay fraction of the core(Depth-1514.47m,1513.42m, 1516.40m) indicate the presence of kaolinite 82.11% ,94.25%and69.74% and illite 17.89%,5.75% and 30.26%.

SEM analysis of conventional core-2 Scanning Electron Microscope study of sandstone samples with

moderate to good intergranular porosity .The intergranular porosity are occupied by authigenic kaolinite and patchy calcite cement and quartz overgrowth.

MEGASCOPIC STUDY OF CONVENTIONAL CORE-4( Pariwar formation)

Megascopically the core comprises dark grayish brown ,hard and compact , fine to medium grained, sub-angular to sub rounded, micaceous and sandstone with ferruginous cement. Effect of chemical weathering.

Core Log CC-1(lower Goru Member) CC-2(lower Goru Member) CC-3(lower Goru Member) CC-4(Pariwar Formation)

CONCLUSION Petrographically the sandstones of Lower Goru

membe are calcareous quartz arenites and quartz wacke.

The lower Goru Member of Goru formation has been deposited in an overall regressive phase with intermittent marine Incursions.

Presence of glauconitic sandstones and shales are indicative of shallow marine conditions.

Ferruginous sandstone, grey shales with brachiopod shell, and current bedding are suggestive of continental to parallic environment.

The Lower Goru Member could be either shallow water marine or extensive alluvial plain eustarine deposits where both wind and water had their role to play.

The Pariwar Formation mostly comprised moderately sorted sandstone having good reservoir characteristics

CONCLUSION(continued) Through Petrographic observations ,it is noted that

the porosity has been deteriorated due to occlusion of Ferron Calcite cement as well as siderite in the intergranular spaces of sandstone .This inturn reduces the permeability. In some instances Quartz overgrowth is also noted which has adverse effect on Petrophysical character of Reservoir.

X-Ray Diffraction analysis of matrix of the sandstone revealed the presence of Clay minerals like Kaolinite ,illite and smectite as detrital clay .

SEM studies has brought out intergranular porosity clearly seen on the images ,however at places due to presence of framboidal pyrite , Smectite and Illite along with altered mica and altered feldspar the reservoir quality of sandstone is deteriorated

Thank You