Publications

A common fallacy in evaluating shale gas potential in a basin is treating similar to those produced in the United States. In fact, each basin has unique characteristics that influence shale facies type and depositional. The Lower Baong shale is responsible for source rock in the sandstone reservoirs in the oil and gas fields in the North Sumatra Basin. This study reviews data and interpretation from the laboratory, drilling, wireline well logs, and seismic studies through the integrated study of geochemistry, geomechanics and geological synthesis of the Lower Baong Formation. An understanding of shale geochemistry, mineralogy, and geomechanics is important to understand how the potential of the shale reservoir to produce reserves when stimulation is carried out. Geochemical laboratory analysis is used to determine the richness, maturity, and kerogen type. This information is limited to a certain depth point, so it is necessary to conduct calibrations to estimate the shale productive reservoir interval on a wireline log scale. Limited core data and rock mechanics laboratory analysis represented by mineralogy can also calibrate with brittleness index. Thus, the geochemical and geomechanical log model tied to the seismic data is a useful tool for formation evaluation and for broadening the understanding of the distribution of the shale reservoir facies. Understanding shale facies is needed to design a fracturing horizontal hole in more detail. This study also classifies the shale based on organic richness, maturity, type, shale strength, shale brittleness, and clay content. Shale facies in the Lower Baong shale can be divided into three facies of the sweet spot area. Siliceous calcareous mudstone has a high potential for shale gas with 2–3.5% of TOC, II–III type of kerogen type, maturity depth from 2300 m, 350–425 m of sweet spot thickness, 10000–18000 psia of UCS, 3000–4000 psia of the Young’s modulus, 0.18–0.22 of the Poisson’s ratio, and is associated with foreland basin fill deep. Silty-shaly calcareous mudstone has the medium potential for shale gas, which is associated with the foreland basin fill slope. Silty-shaly dolomitic mudstone is associated with foreland basin fill edge that has a high potential for shale. The integrated approach for geochemistry and geomechanics is expected to reduce the risk of shale gas exploration.