U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011–3131

November 2011

World Petroleum Resources Project

Assessment of Potential Shale Gas Resources of the Bombay, 

Cauvery, and Krishna–Godavari Geologic Provinces, India, 2011

Figure 1. Locations of the Bombay, Cauvery, and Krishna–Godavari 

Provinces in India (red) and the areas of the shale gas assessment units 

(AUs) (green) that were assessed in this study. Maps of AUs were based 

on data from Directorate General of Hydrocarbons (written commun., 

2009). Dashed boundaries indicate lines of control and area of Indian claim.

Introduction

The U.S. Geological Survey (USGS), in cooperation with the 

U.S. Department of State, is assessing the potential for unconventional oil 

and gas resources (shale gas, shale oil, tight gas, coalbed gas) in priority 

geologic provinces worldwide. This report summarizes the geologic model 

and assessment of potential shale gas resources of the Bombay, Cauvery, 

and Krishna–Godavari Provinces, India. These geologic provinces 

(Cambay, Cauvery, and Krishna–Godavari) are located along the margins 

of the Indian subcontinent (fig. 1) and contain the basins that were assessed 

in this study. The basins are interpreted to have originated as rift/sag basins 

and they control the distribution of Mesozoic and Cenozoic source rocks 

as well as the shale gas resources in the respective geologic provinces.

Cambay Basin

The upper Paleocene to middle Eocene Cambay Shale is interpreted 

to be a major source rock in the Cambay Basin (Directorate General of 

Hydrocarbons, Cambay Basin, written commun., 2009). Cambay Shale 

was deposited in deltaic and nearshore marine environments in the 

northern and central parts of the basin, and in deeper marine environments 

in the southern part of the basin. Therefore, this source rock presumably contains greater amounts of type II kerogen southward in the basin. 

Thermal maturity increases from north to south across the basin. Although 

the Cambay Shale is in the oil-generation window in the north, it is in 

the gas-generation window in the south. At the base of the shale, vitrinite 

reflectance (Ro) values are greater than 1.1 percent. Total organic carbon 

contents (TOC) are greatest in the basin depocenters, with concentrations 

greater than 4 weight percent.

Cauvery Basin

Potential source rocks in the Cauvery Basin include shales of 

the Lower Cretaceous Andimadam Formation and the Lower to Upper 

Cretaceous Sattapadi Shale and its stratigraphic equivalents (Directorate 

General of Hydrocarbons, Cauvery Basin, written commun., 2009). The 

shales are interpreted to have been deposited in marine environments. The 

Sattapadi Shale contains 2 to 2.5 weight percent TOC and is thermally 

mature for hydrocarbon generation in deeper parts of the basin. Ro values 

vary from approximately 1.0 percent to as much as approximately 1.5 percent. Kerogen types are predominantly type III with minor amounts of 

type II.

Krishna–Godavari Basin

The Upper Jurassic to Cretaceous Raghavapuram Shale and its 

stratigraphic equivalents are inferred to be the main source rock for much 

of the Krishna–Godavari Basin (Directorate General of Hydrocarbons, 

Krishna–Godavari Basin, written commun., 2009). The Raghavapuram 

Shale was deposited in marginal marine to inner shelf environments, 

whereas the stratigraphically equivalent Chintalapalli Shale accumulated 

under bathyal conditions. The shale contains as much as 2.4 weight percent TOC, and its thermal maturity ranges from immature to mature with 

respect to gas generation. Type III kerogen is most common, but type II is 

present where the shale was deposited under deeper marine conditions.

Geologic Model for Assessment

The geologic model that forms the basis for the assessment of 

Bombay, Cauvery, and Krishna–Godavari Provinces is that the shales are 

self-sourced. Gas was generated in Mesozoic and Cenozoic organic-rich 

shales and filled matrix and organic matter porosity in the same shales. 

Evaluations for each of the shale gas systems and areas to be assessed 

used five criteria: (1) average TOC of 2 weight percent or greater; 

(2) presence of type I, II, or IIS kerogen; (3) thermal maturity equivalent 

to at least 1.1 percent Ro; (4) presence of thermogenic gas; and (5) net 

source rock thickness of 15 meters or more. All five of these criteria must 

be present at one place to continue with an assessment (Charpentier and 

Cook, 2011).

For each of the assessed provinces, the presence of organic-rich 

shales, the presence of type II in relation to type III kerogen, the potential for matrix storage of gas, and the thermal windows for oil in relation 

to gas generation are all subject to significant geologic uncertainty. 

Consequently, shale-gas accumulations in the United States were used 

as geologic and engineering analogs in the USGS assessment of these 

provinces (Charpentier and Cook, 2011). Analog data from U.S. accumulations included estimated ultimate recoveries from shale-gas wells, 

average drainage areas of wells (cell sizes), and ranges of success ratios. 

Key assessment input data are listed in table 1.

Printed on recycled paper

!

20°

15°

70°

Laos

75° 80° 85°

Mumbai Bombay

Province

Krishna–Godavari

Province

Cauvery

Province

INDIA

Cambay Shale

Gas South AU

Sattapadi–Andimadam

Shale Gas AU

Raghavapuram

Shale Gas AU

INDIA

0 100 200 KILOMETERS 

0 100 MILES

Using a performance-based geologic assessment methodology, 

the U.S. Geological Survey estimated a technically recoverable mean 

volume of 6.1 trillion cubic feet of potential shale gas in the Bombay, 

Cauvery, and Krishna–Godavari Provinces* of India.

*

The term “provinces” refers to geologically defined units assessed by USGS 

for the purposes of this report and carries no political or diplomatic connotation.
Assessment input data Cambay Shale Gas South AU Sattapadi-Andimadam Shale Gas AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 110,000 230,000 350,000 230,000 200,000 300,000 650,000 383,333

Average drainage area of wells (acres) 120 150 180 150 120 150 180 150

Average EUR (BCF, gas) 0.2 0.6 2.5 0.7 0.2 0.4 2.5 0.54

Success ratios (percent) 75 90 95 87 75 90 95 87

Assessment input data Raghavapuram Shale Gas AU

Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 345,000 700,000 2,000,000 1,015,000

Average drainage area of wells (acres) 120 150 180 150

Average EUR (BCF, gas) 0.2 0.6 2.5 0.7

Success ratios (percent) 75 90 95 87

Table 1. Key assessment input data for shale gas assessment units in the Bombay, Cauvery, and Krishna–Godavari Provinces. EUR (estimated 

ultimate recovery per well), cell size, and success ratios are from U.S. shale gas and shale oil analogs. MMB, million barrels; BCF, billion cubic feet; 

AU, assessment unit. Minimum, mode, and maximum values represent the uncertainty around the mean values, and do not reflect the total variation 

in these parameters. Areas of AUs were calculated from maps produced by Directorate General of Hydrocarbons (written commun., 2009).

Geologic provinces, 

total petroleum systems (TPS) ,

and assessment units (AU)

AU

probability

Field

type

Total undiscovered resources

Oil (MMB) Gas (BCF) NGL (MMB)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Bombay Province, Mesozoic-Cenozoic Composite TPS

Cambay Shale Gas South AU 1.0 Gas 383 787 1,966 924 12 27 69 31

Cauvery Province, Mesozoic-Cenozoic Composite TPS

Sattapadi-Andimadam Shale Gas AU 1.0 Gas 444 887 2,660 1,123 14 31 95 39

Krishna–Godavari Province, Mesozoic-Cenozoic Composite TPS

Raghavapuram Shale Gas AU 1.0 Gas 1,406 3,387 9,133 4,080 28 73 207 90

Total continuous resources 6,127 160

Table 2. Assessment results for potential shale gas resources in the Bombay, Cauvery, and Krishna–Godavari Provinces (technically 

recoverable, continuous resources).

[MMB, million barrels; BCF, billion cubic feet. Results shown are fully risked estimates. For gas fields, all liquids are included under the natural gas liquids (NGL) 

category. F95 denotes a 95-percent chance of at least the amount tabulated. F50 denotes a 50-percent chance, and F5 denotes a 5-percent chance. Other fractiles are 

defined similarly. Fractiles are additive under the assumption of perfect positive correlation. TPS, total petroleum system; AU, assessment unit. Gray shading indicates 

not applicable]

Resource Summary

The results of the USGS assessment of potential shale gas resources 

in the Bombay, Cauvery, and Krishna–Godavari Provinces of India are 

listed in table 2. In summary, the estimated mean volumes of technically 

recoverable petroleum resources are as follows: (1) for the Cambay Shale 

Gas South Assessment Unit (AU) of the Bombay Province—924 billion 

cubic feet of gas (BCFG; range, 383 to 1,966 BCFG) and 31 million 

barrels of natural gas liquids (MMBNGL; range, 12 to 69 MMBNGL); 

(2) for the Sattapadi-Andimadam Shale Gas AU in the Cauvery 

Province—1,123 BCFG (range, 444 to 2,660 BCFG) and 39 MMBNGL 

(range, 14 to 95 MMBNGL); and (3) for the Raghavapuram Shale Gas 

AU of the Krishna–Godavari Province—4,080 BCFG (range, 1,406 to 

9,133 BCFG) and 90 MMBNGL (range, 28 to 207 MMBNGL). The 

ranges of resource estimates for shale gas reflect the considerable geologic uncertainty in these assessment units.

Acknowledgments

We thank Chandra Bhan Singh of the Indian Ministry of Petroleum 

and Natural Gas; S.K. Srivastava, Director General of the Directorate 

General of Hydrocarbons, as well as the staff of the Directorate General 

of Hydrocarbons, including Atanu Banerjee, Malcolm Lall, S. Rath, 

Amitava Roy, S.C. Sarma, B.J. Hazarika, and Sanjay Chawla; and members of Oil and Natural Gas Company Oil India, Ltd., and Gas India, Ltd., 

for sharing data and for educating us on the petroleum geology of the 

basins of India prior to the USGS assessment.

Reference Cited

Charpentier, R.R., and Cook, T.A., 2011, USGS methodology 

for assessing continuous petroleum resources: U.S. Geological 

Survey Open–File Report 2011–1167, 73 p.

Indian Basins Assessment Team

Timothy R. Klett, Christopher J. Schenk, Craig J. 

Wandrey, Michael Brownfield, Ronald R. Charpentier, 

Troy Cook, Donald L. Gautier, and Richard M. Pollastro.

For Further Information

Supporting geologic studies of total petroleum systems 

and assessment units, and reports on the methodology used 

in the assessment of the Bombay, Cauvery, and Krishna–

Godavari Provinces, and assessment results are available at 

the USGS Energy website: http://energy.usgs.gov/OilGas/

AssessmentsData/WorldPetroleumAssessment.aspx.