1. Source Rock Analysis of Cambay Shale, North Cambay Basin, Gujarat, India Vaishali Sharma , Anirbid Sircar School of Petroleum Technology, Pandit Deendayal Petroleum University, Gandhinagar, Gujarat, India
International Shale Gas and Oil Workshop, 2016, New Delhi, India
Abstract
Results
Shale gas exploration and exploitation in India is in nascent stage, basic shale gas specific data requires to be generated. The prognosticated resource potential of Indian Shale gas basins is around 2000 TCF. The petroliferous Cambay basin in western India with interbedded carbonaceous in its thick tertiary sequence forms a potential shale gas prospect. Fine grained, clastic and organic rich Cambay, Tarapur and other Tertiary shales have sources of oil and gas for the basin. The quantity, quality and type of organic matter play an important role in the generation of gas. In this study, around 10 sedimentary rock samples from the North Cambay Basin, Sanchor-Patan Tectonic Block were analyzed by Rock –Eval Pyrolysis - 6 to predict the generation and accumulation of gas in this basin. This technique was adopted to obtain the independent parameters on organic matter composition, its thermal maturity, and kerogen typing. Also, a mathematical expression of Hydrogen Index (HI) vs. Rock Eval maximum temperature (Tmax) pathline for a particular kerogen is generated to understand i) the characterization of the kerogen with respect to its original generation potential and ii) migration channels. The geochemical study suggests that the sections are not mature at this moment but on complete thermal maturity may act as a good source rock. The present study is suitable for the assessment of hydrocarbon potential of source rock and rapid geochemical characterization of sedimentary organic matter. r
Fig. 4 HI vs Tmax
Fig 3 S1 vs Tmax
Objective
The overall objective of the study is to –
1. Obtain the organic matter composition, kerogen typing and thermal maturity of the shale samples collected from the North Cambay Basin.
2. Generate the gas-source genetic relationship by rapid geochemical characterization of sedimentary samples.
3. Predict the relative proportion of hydrocarbon (oil/gas) generated and expelled from the source rock.
4. Identify the migration channels/ pathways.
Fig.5 Stratigraphic Log
Methodology
HI = S2/TOC * 100
OI = S3/TOC * 100
Fig. 6 HI vs OI
Fig. 7 HCG/HCE vs Depth
PI = S1/(S1+S2)
PC = (S1+ S2 )/ 10
Conclusions
Idealized geochemical log based on Rock-Eval pyrolysis, TOC, HI and OI, HCG and HCE of samples from the well showing evidence of:-
Oxidized organic matter, which might represent a well additive;
Thermally immature source rock containing Types III Kerogen (Gas Prone);
A non-source interval;
Migration history of hydrocarbon after expulsion;
The source and the reservoir coexists with each other in a cannibalistic manner.
TR = 1 – (HI/HIO)
HCE = HCG – S1 *1.3
HCG = S2 / (1-TR)
Study Area: North Cambay Basin
References
Arfaoui Adel, Montacer Mabrouk, Kamoun Fekri, Rigane Adel (2007). Comparative study between Rock Eval Pyrolysis and biomarkers parameters: A case study of Ypresian source rocks in central – northern Tunisia. Marine and Petroleum Geology, 24,
Banerjee, A., Jha, M., Mittal A.K., Thomas N.J. and Misra K.N. (2000). The effective source rocks in the north Cambay Basin, India. Marine and Petroleum Geology, 17,
Bhandari, L.L., and Chowdhary, L.R. (1975). Stratigraphic analysis of Kadi and Kalol Formations, Cambay Basin, India. AAPG Bulletin
Chandra, P.K., and Chowdhary, L.R. (1969). Stratigraphy of the Cambay Basin. Bulletin Oil and Natural Gas Commission (ONGC), Dehradun, India, 6,
Dayal A.M., Mani Devleena, Mishra Snigdharani, Patil D.J. (2013). Shale gas prospects of Cambay Basin, Western India. Geohorizons, 26.
Mathur, L.P., Rao K.L.N., and Chaube, A.N. (1968). Tectonic framework of Cambay Basin, India. Bulletin: Oil and Natural gas Commission (ONGC), Dehradun, India, 5,
Tissot, B.P. and Welte, D.H. (1984).Petroleum Formation and Occurrence. Springer, 699.
Fig .2 Samples from North Cambay Basin, Patan (Nanachiloda)
Fig 1 Location Map of Study Area : North Cambay Basin
Acknowledgement
Studies
Cambay Basin
G&G Studies
Shale
Cambay Shale
Tectonic Block
Sanchor-Patan Block
Field
Nanachiloda, Patan
Geochemical Analysis
TOC
1.1 % %.
Kerogen Type
Type III
Tmax
429 to 440 ˚C
S1 (mg HC / g rock sample )
0.08 to 0.29
S2 (mg HC / g rock sample )
0.05 to 0.66
HCG and HCE
0.074 to0.12 and
0.623 to -0.09
The authors are grateful to School of Petroleum Technology, PDPU for granting the permission to present this paper at International Shale Gas and Oil Workshop, New Delhi, The authors are also thankful to Mr. Jai Mehndiatta (B.Tech –Petroleum Engineering, V Semester Student) and colleagues for their help and support rendered during this work.
Benefit to Industry/Academia
Expertise to qualify and quantify S1, S2, S3, S4, TOC, HI, OI etc. for shales in Cambay Basin
The industry will benefit from the characterization of shale (source analysis) in a systematic manner, probably first time from petroleum institute.
Accumulation and expulsion of hydrocarbon within shales is demonstrated in this poster with its efficacy. The same may be of immense benefit to the academician, industry persons and researchers if sample analysis can be done for upper and lower cambay shale for five major tectonic blocks with in Cambay graben.
This is the first step to be understood before conducting hydraulic fracturing and the approach will help the industry at large for preparing a data repository on shale gas/oil.
Table 1 Rock Eval Pyrolysis Results (Geochemical Analysis)