Shale gas characterization based on geochemical and geomechanical to determine hydrocarbon potential at Tamiang Deep, North Sumatra Basin

Shale gas remains one of the trending topics in the petroleum industry. Indonesia has a great potential shale gas resource, and both government and oil companies have promoted the development of shale gas. Geochemical and geomechanical parameters are important aspects for exploring new shale gas play, and it provides significant information to optimize production plan and stimulation design. However, there is limited research on correlations inter petrophysical parameters for shale gas reservoirs. The study area is located on the southeast border of the North Sumatra Basin. Lower Baong Formation shales are believed to be favorable shale gas targets with a dominant shale lithology. The Baong Formation occurs at depths from 1.465 m to 3.224 m in the study area with the thick mudstone, dominated by gray, brown to black calcareous shale rich in foraminifera, indicating a marine environment. The Baong Formation age varies from the Lower Miocene to Middle Miocene can split into three vertical units: Upper Baong, Middle Baong, and the dominantly shale Lower Baong. This research is aimed to characterize and identify shale hydrocarbon by examining the Total Organic Carbon (TOC), Brittleness Index (BI), Hydrogen Index (HI) and maturity parameters. Various methods were used to analyze these parameters, including geochemistry, mineralogy, petrophysics, cross plotting, and seismic interpretation. Our analysis on rock evaluation and petrographic data shows that TOC varies between 0,1% to 3,7%, vitrinite reflectance of 0.4 - 0.7%, HI varies from 31 - 171, and maximum temperature (Tmax) from 444 - 465°C. TOC resulted in a poor to good category. A cross plot of the HI and Tmax in the van Krevelen diagram revealed the dominant kerogen types as II and III. The kerogen is considered as early mature to mature. The brittleness index of the shale formation of the research area is categorized in less brittle to brittle. The prospective areas for the development of shale hydrocarbon are the sequences of MFS-2, MFS-3, SB-2 and SB-3 with the potential of shale oil.