1. Gas Reservoir Characteristics of Shale Beds in India
By,
V. A. Mendhe, Subhashree Mishra, Alka D. Kamble and
Abhay M. Varade
CENTRAL INSTITUTE OF MINING AND FUEL RESEARCH
(COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH)
BARWA ROAD, DHANBAD - 826015
28-30 November 2013, Manipur University, Imphal
2. Why Shale Gas?
CBM Recovery
The demand of gas is significantly rising in India.
India Natural gas demand is currently about >180 MMSCMD, while
the domestic supply is only 80 MMSCMD.
Methane Gas derived from shale is a clean energy resource.
Shale gas is contained within the shales predominantly in adsorbed
form, in the macro, meso & micro-pores and micro-fractures.
The gas is usually thermogenic but it also may be biogenic.
Shale gas boom in recent years has been due to modern
technology in hydraulic fracturing to create extensive artificial
fractures around well bores.
Development in Horizontal drilling within the shale, to create
maximum borehole surface area in contact with the shale.
3. Sedimentary
Basin of India
Source: DGH
Sedimentary area of 3.14
million Sq. Km.
26 sedimentary basins
1.35 million Sq Km. area is
in deep water
1.79 million Sq Km. area is
in onland and shallow
offshore.
At present 1.06 million Sq
Km. area is held under
Petroleum Exploration
6. Shale Gas Potentiality Study in India
Determined in-situ gas content by Direct method including
desorbed gas, lost gas and residual gas.
Constructed adsorption isotherm and degree of gas saturation
of shale
TOC and Pyrolysis of shale samples
Surface area, pore size and pore volume
9. In-Situ Gas Content by Direct Method
Lost Gas (Q1)
Desorbed Gas (Q2)
Residual Gas (Q3)
Desorbed Measurements
Lost gas calculation
y = 191.73x - 923.67
R2
= 0.983
-5000
-4000
-3000
-2000
-1000
0
1000
2000
3000
4000
5000
0.00 5.00 10.00 15.00 20.00
Square root of Time (min)
Cumm.
desorbed
gas
(cc)
12. TOC and Pyrolysis of shale samples
• Shale contains sufficient amount of organic matter.
• TOC is essentially the total amount of organic matter
(kerogen) in a given sample of rock and TOC initiates
the evaluation of shale play.
• Shale should be subjected to the geologic processes
needed to convert organic material to oil and/or gas.
• Rock-Eval Pyrolysis evaluates the type and the
maturity of the organic matter as well as
determining its petroleum potential.
• Vitrinite reflectance (VRo) is used for determining the
thermal maturity of the shale.
13. OI vs. HI of Shale Samples
0
150
300
450
600
750
0 50 100 150 200
HI
(mg
HC/g
TOC)
OI (mg CO2/g TOC)
Type I
(Oil Prone)
Type II
(Oil Prone)
Type III
(Gas Prone)
Type IV Dry Gas
14. 0
100
200
300
400
500
600
700
800
900
1000
0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
HI
(mg
HC/g
TOC)
VRo (%)
Type I (Oil Prone Lacustrine)
Type II (Oil Prone Marine)
Type III (Gas Prone)
Type IV
Oil Window
Wet Gas Window
Dry Gas Window
VRo Vs. HI of Shale Samples
15. 0
100
200
300
400
500
600
700
800
900
1000
360 390 420 450 480 510
HI
(mg
HC/g
TOC)
Tmax °C
Type IV
Type III
(Gas Prone)
Type II
(Oil Prone Marine)
Type I
(Oil Prone Lacustrine)
Ro % = 0.55
Oil Window
Condensate-Wet Gas Window
Ro % = 1.40 Dry Gas Window 0
200
400
600
800
1000
380 400 420 440 460 480 500
HI
(mg
HC/g
TOC)
Tmax °C
I
II
Immature Mature Post mature
0.5% Ro
1.35% Ro
Tmax vs. HI of Shale samples
18. Surface area Method used Result obtained
NK-S2 NK-S3
Single point surface area at P/Po 18.6201m2/g 6.2184m2/g
BET surface area 19.2146m2/g 6.3885m2/g
Micropore area T-plot micropore area 2.1267m2/g -
External surface area T-plot external surface area 17.0879m2/g 6.4602m2/g
Surface area of pores BJH adsorption 14.874m2/g 5.866m2/g
BJH desorption 16.5340m2/g 9.1857m2/g
Pore Volume Single point: Total pore volume (P/Po= 0.99) 0.028492 cm3/g 0.016255 cm3/g
Micropore Volume T-plot micropore volume 0.000798 cm3/g -
Cumulative Volume of Pores BJH adsorption 0.026232 cm3/g 0.015809 cm3/g
BJH desorption 0.026088 cm3/g 0.016518 cm3/g
Pore Size BET method 61.206 Å 101.77 Å
Adsorption average pore width
BJH adsorption 70.547 Å 107.811 Å
BJH desorption 60.115 Å 71.929 Å
DFT pore size Volume in pores < 14.83 Å 14.83 Å
Total volume in pores <= 1,172.33 Å <= 1,475.96 Å
Area in pores > 1,172.33 Å > 1,175.96 Å
Total area in pores >= 14.83 Å >= 14.83 Å
Surface area, Pore size and Pore volume
24. Summary and Conclusions
In-situ gas content of shale core samples is observed to be low.
Large cumulative thickness of shale beds encourage the shale gas
potential even the low gas content of shale beds.
Investigated shale samples have indicated low moisture and sufficient TOC
content.
Investigated shale beds having Type III kerogen and prone for gas generation.
Adsorption isotherm results are compared with the estimated in-situ gas
content of the shale samples revealed that under to moderately saturation of
shale horizons.
Studied shale contains mostly mesopores.
Need of more detailed investigation on Indian shale deposits considering
viz. shale occurrence, thickness, depositional facies, shale mineralogy, type of
clays, TOC content, inorganic content, grain size, porosity and permeability for
better understanding of the shale as gas reservoir.
Enough Shale Reservoir exist in the country.