Publications

The Brown Shale of the Pematang Group is well known as a source rock for the Central Sumatra Basin (CSB) petroleum system. At present, more than 30,000 MMBOE have been discovered in CSB from 199 fields, with cumulative production of about 11,000 MMBOE. The “Metas Field” is located in CSB where Metas-1 was drilled in 1984, and Metas-2 in 1994. Both wells were unsuccessful in locating conventional oil and gas reservoirs, and were plugged and abandoned. Nevertheless, hydrocarbons are known to occurr within the area, and it was considered likely that the Pematang Group has potential as a significant shale hydrocarbon resource play. The aim of this study is to evaluate the hydrocarbon shale potential of the Metas Field. Methods used in this study apply integrated geology, geophysics, petrophysics and geochemical data. Shale samples in Metas-2 consist mainly of quartz with abundant amounts of detrital clay matrix and clay laminae. Porosity and permeability is low (1.7% and 1.93 mD) with brittleness index (BI) of 0.31 (less ductile). Geochemical results for shales of the Pematang Group show maturity levels within the oil window. They are capable of generating shale oil from the early mature phase (6,400 ft depth) and beyond. At Metas-2, Zone C of the Pematang Group Brown Shale at depth interval 8,450 ft to 8,660 ft, has shale hydrocarbon potential, indicated by TOC values of 0.5-1.2 wt %, shale thickness of over 50 ft, BI above 0.48 and rock strength below 10,000 psi. A distribution map of rock strength (RS) and total organic carbon (TOC) shows that Zone C is well developed to the southwest of Metas-1 and Metas-2, in the southern area near the Merah-1, Nasi-1 and Salak-1 wells. The sweet spot area has volumetric resource potential of 76 MMBO per section, with one section equal to 640 acres. Our integrated analysis shows that the Metas Field has resource potential as an “unconventional” shale oil reservoir in CSB. Further analysis of Mirah-1, Nasi-1 and Salak-1 wells will be beneficial to support the results of the study.