Karakteristik Geokimia Organik Minyak Bontang Return Condensate (BRC), Blok Mahakam, Cekungan Kutai, Kalimantan Timur

Amalia, Fina (2026) Karakteristik Geokimia Organik Minyak Bontang Return Condensate (BRC), Blok Mahakam, Cekungan Kutai, Kalimantan Timur. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Telah dilakukan analisis biomarka kondensat BRC blok Mahakam, Cekungan Kutai, Kalimantan Timur untuk menentukan asal usul bahan organik, tingkat kematangan termal, dan lingkungan pengendapan menggunakan metode fraksinasi dan kromatografi gas-spektrometri massa (KG-SM). Biomarka fraksi alifatik teridentifikasi sebagai n-alkana, isoalkana, isoprenoid, sesquiterpenoid, dan sikloheksana. Fraksi aromatik teridentifikasi senyawa derivat naftalena, fenantrena, bifenil, fluorena, dibenzofurana, dibenzotiofena, dan kadalena. Bahan organik sampel kondensat telah mengalami biodegradasi ringan pada skala PM2, yang ditandai oleh kelimpahan isoprenoid pristana sebesar 12,648%. Ion fragmen diagnostik khas pada sampel biodegradasi, yaitu m/z 93 dan 95, memperlihatkan dominasi biodegradasi pada fraksi aromatik dengan kontribusi kecil dari fraksi alifatik. Keberadaan n-alkana menunjukkan deret homolog unimodal (n-C13 – n-C31) dengan dominasi n-alkana rantai pendek sebagai indikator bahan organik alga. Dominasi sumber bahan organik alga ditunjukkan oleh parameter LHCPI, TAR, LMW/HMW, Paq, dan dominasi n-C16 yang merupakan prekusor alga merah serta terdapat input minor dari tanaman terestrial yang dikonfirmasi melalui nilai CPI 1,12. Tingkat kematangan dikonfirmasi oleh parameter MPI, plot CPI dan OEP, plot MPDF, nilai %Rc sebesar 0,94, serta distribusi isomer poliaromatik yang mengindikasikan kematangan yang mendekati puncak jendela minyak. Kelimpahan 9-MP dan 2-MP yang tinggi menunjukkan material organik didominasi campuran kerogen tipe II/III sebagai oil-gas prone. Rasio n-C17/n-C31, n-C29/n-C17, n-C31/n-C19, menginformasikan lingkungan pengendapan geografis akuatik serta distribusi senyawa fluorena, DBF dan DBT mengindikasikan kondensat terendapkan dalam lingkungan transisi lakustrin-fluvio deltaik. Rasio Pr/Ph 8,32 sebagai indikator lingkungan oksidatif pada sampel menunjukkan keterbalikan dengan kelimpahan 8(H)-drimana serta plot DMR dan TMR sebagai indikator pengendapan reduktif. Kondisi redoks heterogen tersebut yang menguatkan adanya keadaan transisi dalam lingkungan pengendapan danau kondensat BRC.
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Biomarker analysis of BRC condensate from the Mahakam Block, Kutai Basin, East Kalimantan, was conducted to determine the source of organic matter, thermal maturity, and depositional environment using fractionation and gas chromatography-mass spectrometry (GC-MS). Biomarkers in the aliphatic fraction were identified as n-alkanes, isoalkanes, isoprenoids, bicyclic sesquiterpenes, and cyclohexanes. The aromatic fraction contained naphthalene, phenanthrene, biphenyl, fluorene, dibenzofuran, dibenzothiophene, and cadalene derivatives. The organic matter in the condensate sample had undergone mild biodegradation at the PM2 scale, as indicated by a pristane isoprenoid abundance of 12.648%. The diagnostic fragment ions characteristic of biodegraded samples, m/z 93 and 95, showed that biodegradation predominated in the aromatic fraction, with a minor contribution from the aliphatic fraction. The occurrence of n-alkanes displayed a unimodal homologous series (n-C13-n-C31), dominated by short chain n-alkanes, indicating algal organic matter. The predominance of algal organic matter was supported by the LHCPI, TAR, LMW/HMW, and Paq parameters, as well as the dominance of n-C16, a precursor associated with red algae; a minor input from terestrial plants was confirmed by a CPI value of 1.12. Maturity was confirmed by MPI parameters, plot CPI and OEP, the MPDF index, an %Rc value of 0.94, and the distribution of polyaromatic isomers, all of which indicate maturity approaching the peak oil window. The high abundance of 9-MP and 2-MP indicates that the organic material was dominated by a mixture of Type II/III kerogen with oil- and gas-prone potential. The ratios of n-C17/n-C31, n-C29/n-C17, n-C31/n-C19, inform the aquatic geographic depositional environment and the distribution of fluorene compounds, DBF and DBT indicate the condensate was deposited in a lacustrine-fluviodeltaic transitional environment. The Pr/Ph ratio of 8.32 as an indicator of the oxidative environment in the sample shows an inverse relationship with the summary of 8β(H)-drimana and the DMR and TMR plots as indicators of reductive deposition. These heterogeneous redox conditions strengthen the existence of a transitional state in the lacustrine environment of the BRC oil.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Alifatik, Aromatik, Biodegradasi, Biomarka, Kondensat BRC
Subjects:	Q Science > QD Chemistry Q Science > QD Chemistry > QD251.2 Chemistry, Organic. Biochemistry
Divisions:	Faculty of Science and Data Analytics (SCIENTICS) > Chemistry > 47201-(S1) Undergraduate Thesis
Depositing User:	Fina Amalia
Date Deposited:	03 Aug 2026 06:54
Last Modified:	03 Aug 2026 06:54
URI:	http://repository.its.ac.id/id/eprint/142042

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