DETERMINATION OF SHALE GAS POTENTIAL OF NORTH SUMATRA BASIN: AN INTEGRATION OF GEOLOGY, GEOCHEMISTRY, PETROPHYSICS AND GEOPHYSICS ANALYSIS

Abstract

A detailed combined geological and geophysical study in North Sumatra basin has shown that
prospective formations for shale play containing gas sweet spots are found to be in shales from Bampo,
Belumai, and Baong Formations. Bampo Formation exhibits low shale gas potential with very low to
medium in organic material contents, maturity index of immature to mature, and moderate brittleness. Rocks
within the formation tend to be reactive to highly reactive to water, with a moderate degree of swelling
capacity. Porosity varies within 5.8 - 7.4 % with permeability ranging from 0.37 to 3.2 mD. Sweet spots in
the formation found around Basilam-1 and Securai-1wells occupy about 21% of the formation. On the other
hand, Belumai Formation shows moderate to good shale gas potential, with low to high organic material
contents, immature to mature levels of maturity, and moderately brittle to brittle. Sweet spot areas in the
formation found around the two wells are about 29% of the formation. For Baong Formation, analysis
reveals moderate to good shale gas potential, with low to medium contents of organic material, immature
to mature in maturity index, moderately brittle to brittle in brittleness, and tendency of being reactive
to highly reactive to water but with low degree of swelling capacity. Sweet spots in the formation found
around the two wells occupies are roughly 11% of the total formation volume in the area. Basin modeling
leading to gas resources estimation for Baong, Belumai and Bampo Formations has led to estimated
volumes of 6,379 TCF, 16,994 TCF, and 25,024 TCF, respectively, with a total amount of 48,397 TCF.
The resources figures are speculative in nature and do not incorporate any certainty and efficiency factors.