Methane sorption capacities and geochemical characterization of Paleozoic shale Formations from Western Peninsula Malaysia: Implication of shale gas potential

Abstract

Thick sequences of overmatured Paleozoic black shales Formation were deposited in the Western Peninsula (WP) Malaysia, which can be considered as the potential shale gas reservoir. Therefore, to study the shale gas potential of the Paleozoic (Silurian-Permian) shale Formations, 146 samples from seven Formations were collected from WP Malaysia. A combination of methane sorption capacities, geochemical and trace element studies have been performed on the shale samples. The results indicate that the high pressure (up to 15 MPa) methane sorption capacity of the Silurian-Devonian, Devonian, Carboniferous, and Permian shales are between 0.079 and 0.154, 0.056 and 0.113, 0.052 and 0.094 and 0.085 and 0.169 mmol/g rock, respectively, at 30°C. Methane sorption capacities of the WP Malaysia shale were found to be greatly similar to sorption values of hot shales from Posidonia (Germany), Barnett (USA) and Longmaxi (China) shales. The measured total organic carbon (TOC) generally exceeded 2 wt% (average of 4 wt%), except for Carboniferous shales (>1 wt%). The biomarker analysis and Tmax values revealed that the kerogen has evolved into the metagenesis stage. The organic matter is likely comprises hydrogen-rich kerogen deposited under marine conditions in dysoxic to anoxic environment. After a comprehensive analysis, the Silurian-Devonian, Devonian and Permian shales in Western Peninsula Malaysia can be classified as potential gas shales based on their high TOC contents, presence of type III kerogen, high thermal maturity and significant methane sorption capacities.