CHARACTERISATION OF OILS AND SOURCE ROCKS IN JABUNG AREA, JAMBI SUB-BASIN

• Main Author: Parulian Marpaung, Lambok
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69612
• Institution: Institut Teknologi Bandung

Jabung area and whole Jambi Sub-Basin, Sumatra, has been a prolific target of exploration since 1990. A number of oil and gas fields has been discovered and produced. However, the petroleum system of the region has not been fully understood since there has no detail geochemical study been conducted. This thesis attempts to understand one of the geochemical aspects of Jabung area, namely characterisation of oils and source rocks. The evaluation of this study of the area is based on 21 oil samples from various reservoirs and 14 rock samples. Characteristic of oils and source rocks were determined by kerogen types, Rock-Eval analyses, bulk oil properties, gas chromatography, biomarker and carbon isotopes of the oil and source rock samples. Oil to oil and oil to source correlations were applied to interpret the most likely source/s of the existing oils. Maturation modeling of the expected source/s was conducted to establish the history of oil generation and migration. Oils of Jabung area were commonly derived from terrestrial source rock, having suboxic-oxic environment (fluvio-deltaic). Oils of this area could be divided into two families: DI and DII. DI (Jabung Tengah) family is more terrestrial, more oxic, less oleanane content, and higher hopane/sterane ratio compared with the DII (Jabung Timur) family. Oils belong to the DII family have been estimated that their source rock is relatively younger than that of the DI family. Source rocks of Talang Akar Formation were generally constructed by type II and III kerogens with type III being more predominant. Shales of Gumai Formation were marine deposited, being rich of marine algae. Based on biomarker analyses, source rock of Talang Akar has been mature. Correlation and source geochemistry evaluation conclude that the shales and coals of Talang Akar are the main source rocks of oils in the Jabung area. The oil generation was in Early Miocene in Betara deep and oils were generated in Mid-Miocene in Geragai, Tungkal and Kabul deep. Generally, oils migrated toward young structures that were formed during Plio-Pleistocene.