A suite of oil seep samples collected from the Lariang and Karama Basins, West Sulawesi, Indonesia, have been analyzed using GC and GCMS techniques. Their biomarker compositions have been used to reveal the likely source rock that produces oil. These oil seep samples contain a range in both the concentration of hydrocarbons present and certain level of biodegradation experienced. All sterane m/z 217 data display a familiar pattern of steranes with carbon numbers from 27 to 29 together with pregnane and homo-pregnanes, including rearranged steranes. Triterpane (m/z 191) data show a moderate content of tricyclic terpanes (Tri/C 30 H), medium to high ratio of norhopane/hopane (C 29 /C 30), and medium to high abundant land plan marker such as resin bicadinanes(Bic/C 30 H) and oleananes (Ol/ C 30 H). The presence of high abundant oleananes in these samples has been interpreted as the evidence for a marine influence during early diagenesis that may occur by marine or via re-deposition of peat organics in marine sediments. Hence, these results state that the organic matter facies for their source rock oil seep samples from the West Sulawesi region are detected as mixed between allochthonous macerals from typical terrestrial higher plants transported into the basin from distal swamps and soils and some marine organic matter.

The eastern part of the Makassar Strait has not achieved significant success in the petroleum exploration stage. In general, exploration wells in this area have not found hydrocarbons to date. Most of the problems experienced by these wells are geochemical-related, including the absence of a source rock where the hydrocarbon is formed, immature source rock, and low volume of hydrocarbon. Therefore, this study aims to find potential Eocene source rock in West Sulawesi. It commenced by determining the paleofacies followed by the geochemical analysis of well cutting and surface samples. The geochemical analyses conducted are total organic carbon (TOC), rock eval pyrolysis (REP), kerogen type, vitrinite reflectance (VR), and gas chromatography/mass spectrometry (GC/MS). The samples that have a potential as an Eocene source rock were coal, as well as carbonaceous and marine shale. Based on the plotting of relative abundance for sterane (C 27 -C 29 ), the coal and carbonaceous shale had the input from terrestrial organic material with a contribution from marine, while marine shale had the input from marine organic material and contribution from terrestrial. Furthermore, coal and carbonaceous shale had a relatively high proportion of C 29 sterane compared to C 27 and C 28 , while marine shale had a relatively high proportion of C 27 compared to C 28 and C 29 . The higher plants also contributed to the organic matter in carbonaceous shale and coal samples, as indicated by the abundance of oleanane/C 30 hopane and the other significant content of resin biomarker. In accordance with the objectives of the study, it was found that during the Eocene, the type of source rock in the eastern side of the province varied, starting with coal and carbonaceous shale in the upper intertidal-fluviodeltaic environment, and marine shale sediments from the source facies of marine algal.

<div><table cellspacing="0" cellpadding="0" align="left"><tbody><tr><td align="left" valign="top"><p>Sumur eksplorasi LYS dan KYS merupakan dua sumur pertama yang dibor di Blok Bdg, daratan Sulawesi Barat oleh kontraktor Wilayah Kerja Eksplorasi. Beberapa analisis dan evaluasi geokimia dilakukan pada sampel sumur LYS dan KYS, yaitu analisis karbon organik total (TOC), <em>rock eval pyrolysis</em> (REP), reflektansi vitrinit (VR), jenis kerogen, kromatografi gas (GC), dan kromatografi gas/spektrometri massa (GC/MS). Untuk mengilustrasikan perbedaan dalam sejarah pembenaman dan kematangan thermal antara sumur LYS dan KYS, pemodelan sejarah pembenaman dan kematangan thermal telah dilakukan pada kedua sumur ini. Sumur LYS-1 merupakan sumur darat dangkal yang hanya melakukan penetrasi hingga Miosen Awal, yang secara thermal belum matang, sedangkan sumur KYS menembus hingga Eosen. Sedimen berumur Eosen diasumsikan matang lebih awal (sekitar 10Ma), karena adanya sedimen berumur Oligosen dan Miosen yang lebih tebal. Berdasarkan nilai TOC, VR, Tmax, profil kematangan, dan pemodelan sejarah pembenaman dan thermal dari sampel sumur LYS dan KYS, diasumsikan bahwa sampel sumur KYS lebih matang dibandingkan sampel sumur LYS.</p></td></tr></tbody></table></div>