UNCONVENTIONAL HYDROCARBON POTENTIAL OF CAMBAY SHALE, JAMBUSAR-BROACH AREA, CAMBAY BASIN, INDIA: IMPLICATION ON SEQUENCE STRATIGRAPHY

Abstract

An evaluation of unconventional hydrocarbon potential (shale gas / oil) of the Cambay Shale Formation in Jambusar-Broach area of the Cambay Basin, India is the core theme of this thesis. Shale plays (Shale gas / oil) are important unconventional sources of energy and playing major role to fulfil increasing global energy demand as an alternative energy resources. The Cambay Basin consists of thick shale envisaged to be good shale play resources. So far, five wells for exploration shale play have been drilled in Broach depression, however, no significant discovery is made. Main reason for the failure is exploration of the Cambay Shale Formation is carried out based on isopach map and maturity models. However, there is a huge difference between established American and Canadian shale plays and Cambay shale viz. Cambay Shale and unlike the global shale plays which have been explored based on any one or two parameter, exploration of the Cambay Shale requires analysis of many parameters. This has given an impetus to look into the Cambay Shale Formation in detail to understand its unconventional hydrocarbon potential through an integrated approach. The approach includes; heterogeneity characterization of the Cambay Shale by identification & correlation of sequences and their inorganic and organofacies characterization. After integrating all these studies a 3D static geological model is generated. Then, 3D petroleum system modelling (PSM) coupled with play chance mapping (PCM) is carried out. Cambay shale is considered to be homogenous, however, this study suggests that the Cambay Shale is not homogeneous “shale”. Heterogeneity of the Cambay Shale Formation is characterized based on the analysis of core & cuttings samples, interpretation of electrolog data and its correlations across the wells at various measures. In total eleven 3rd order transgressive-regressive (T-R) sequences have been envisaged by the formation. Sedimentological analysis of core and cuttings samples suggests three types of facies. Coarsening upward HST is distinct in the top part while the fining upward TST is distinct in the bottom part of each TR sequence and separated by marine flooding events. HST part dominantly consists of quartz & carbonate mineral fractions in contrast to the TST part. Accordingly mineral fraction maps are generated for the sequences. This approach has provided broad dispersal of brittle and ductile areas within sequences.