Geochemical Correlation of Gas and Condensate from The Lower Seurula Reservoir with Potential Source Rocks in The North Sumatra Basin

Wiendra Akhmad Faridsyah; Very Susanto

doi:10.29017/scog.v49i3.2179

Authors

Wiendra Akhmad Faridsyah Institut Teknologi Bandung and PT Pema Global Energi
Very Susanto Institut Teknologi Bandung

DOI:

https://doi.org/10.29017/scog.v49i3.2179

Keywords:

gas condensate, geochemical correlation, Lower Seurula Formation, Arun Field, North Sumatra Basin

Abstract

Recent exploration activities in Block “B” of the North Sumatra Basin, including the acquisition and processing of 610 km² 3D seismic data followed by a two-well exploratory drilling campaign, led to gas and condensate discoveries within the Late Miocene sandstone reservoirs of the Lower Seurula Formation. The campaign targeted two structures: Arun Overburden (AOB), located above the Arun Structure, and Rayeu. Previous studies have focused primarily on the giant Arun and SLS Fields due to their substantial hydrocarbon reserves. Consequently, direct evidence for the source rock charging reservoirs younger than the Early Miocene Peutu Formation carbonates was lacking. Gas and condensate samples from the newly discovered Rayeu CA and AOB-1 wells, along with samples from the Arun and SLS fields, were acquired and subsequently analyzed in the laboratory. Characterization and correlation of both source rock and hydrocarbon samples are the most appropriate methodologies for evaluating their genetic relationship. Although condensates from Arun and AOB-1 exhibit retrograde phase behavior, reliable geochemical interpretations and correlations were obtained. The results indicate that gas and condensate from both Peutu carbonate and Lower Seurula sandstone were generated from a highly mature source rock dominated by algal organic matter, with only a minor contribution from higher plants. These findings suggest that multiple reservoir objectives in “B” Block, particularly in the Lhok Sukon Deep sub-basin, most consistently correlated with a mature Bampo-type marine shale source facies.

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