OMBDLIN BASIN: A PROSPECT FOR SHALE GAS IN INDONESIA

摘要

Shale gas refers to natural gas that is trapped within shale formations. Shales are fine-grained sedimentary rocks that can be rich sources of petroleum and natural gas. Shale-gas occurrence appears to be of dual predominantly biogenic origin, resulting from metabolic activity of methanogenic bacteria; and thermogenic, the result of thermal maturation of kerogen. However, combined biogenic-thermogenic gas accumulations can occur. Basically, for black shales to have produced gas they must fulfill threecriteria: thermal maturity (vitrinite reflectance), sufficient reservoir thickness, and total organic carbon content. This paper will explain about potential natural shale gas in Ombilin Basin. The basin is a Tertiary intermontane basin located within the Barisan Mountain Range of West Sumatera. Formation nomenclature in this basin are Sangkarewang Formation, Sawahlunto Formation, Sawahtambang Formation and Ombilin Formation. The Sangkarewang Formation is comprised of predominantly organically rich succession, deposited in a restricted to anoxic deep-water to marginally lacustrine environment. This shale exhibits the criteria required for potential natural gas recovery: adequate total organic carbon (TOC), thermal maturity, organic petrology, mineralogy, and geologic characterization.