Source rock characterization and its influence on pore volumes in Lower Gondwana shale samples of Damodar Valley, India

Abstract

This study aims to investigate the hydrocarbon potential and storage capacity of five shale samples collected from Barren Measure Formation of Damodar Valley in India. Characterization of source rocks was performed using rock eval pyrolysis and, pore volumes were measured using the MICP and low pressure CO2 adsorption methods. Results of pyrolysis show excellent TOC content ranging between 4.24% and 9.78%. Variation in Tmax values from 437 to 447 °C indicates that the thermal maturity is within the oil window range. Values of HI (110–211 mg HC/gm TOC) and OI (3–36 mg HC/gm TOC) indicate a mixture of Type II and Type III kerogen which, can be a good source rock for oil and gas. Pore spaces present within the rock act as storage for the generated hydrocarbons. Pore volume and pore-size are the major influential factors for the storage and production capacities of hydrocarbon reservoirs. Results of MICP experiments show high porosity values (≥13%) for all the samples. Macro and mesopore volumes calculated using the MICP method are varying within the range between 0.074 and 0.17 cc/mg. Low-pressure adsorption using CO2 gas was adopted to estimate the micropore volume of the samples. The volumes of micropores are varying between 2.3 cc/gm and 4.1 cc/gm. Pore volumes measured using both techniques were arithmetically summed up to calculate the total pore volume of the samples. Source rock characters shows a change in trend below 475 m. High pore volumes indicate a good storage capacity for the studied samples. Having the potential to be a good source rock for hydrocarbon and also containing higher pore volume to store hydrocarbon, Barren Measure shale can be considered as a good source as well potential hydrocarbon reservoir rocks among Indian shale formations.