THE SYNRIFT FACIES DISTRIBUTION MODELING OF PRE-NGIMBANG AND NGIMBANG FORMATIONS AND ITS IMPLICATION TO THE HYDROCARBON EXPLORATION IN LAUT BALI TIMUR AREA EAST JAVA-LOMBOK BASIN

• Main Author: KUSNANDAR, YUYUS
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/17705
• Institution: Institut Teknologi Bandung

East Java-Lombok basin is one of the promising exploration targets for synrift plays. However, although all the required ingredients for hydrocarbon accumulation found in the area, in fact the exploration success ratio is relatively low. The previous studies suggested that in general the dry holes in East Java-Lombok Basin were mostly caused by the migration problems due to the absence or lack of communication between reservoirs and source rock in the area. The synrift sandstone deposit of Ngimbang and Pre-Ngimbang Formations is considered to be the main migration carrier bed and in some cases it is also act as the active reservoir (L46-1 well & Pagerungan field). While the synrift lacustrine shale act as the hydrocarbon main source rock and some act as the seal. So it is very important to understand the synrift facies distribution in this area, in order to reduce the migration uncertainty, predicting the reservoir geometry and other general implication to the hydrocarbon exploration in this area.<p>This research is designed to generate the facies distribution model of synrift deposit by using the 3D geo-cellular modeling technique which integrated the existing well and seismic data with a fine conceptual geological model from the present day analogues. The research is divided in to five main steps; the rift basin identification and reconstruction, the synrift depositional units division, the lithology recognition from the well vs. seismic attributes, the facies distribution modeling and finally analyses of the modeling results.<p>The study results show that the rift basin structural geometry in the study area is arranged by a series of northward dipping half-grabens with similar polarity in a relatively WNW-ESE general trend, with the average size is about 20 km in length and 10 km in wide. The rift basin evolution in study area can be divided into three main phases: rift initiation, rift climax and immediate post-rift. The modeling results show that each phase of rift evolution has a different facies distribution; the "rift Initiation" was dominated by fluvial conglomeratic-coarse sandstone and sandstone facies. The rift climax is dominated by the lacustrine shale, fine sand and sandy-shale facies. While the immediate post-rift unit is dominated by the fluvio-deltaic conglomeratic-coarse sandstone and sandstone facies. Each facies has an important role to the petroleum system aspects and implication to the hydrocarbon exploration in this area.