TECTONIC INVERSION IN SYN-RIFT SEDIMENTS AND ITS IMPLICATION ON HYDROCARBON TRAPPING IN NORTH SUMATRA BASIN, ANDAMAN SEA REGION

• Main Author: Banukarso, Mulyono
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/73134
• Institution: Institut Teknologi Bandung

Andaman Sea is part of the deep-water area of the North Sumatra basin, with water depths ranging from 500 meters to 1500 meters. Deepwater exploration activities with the target reservoir syn-rift sediments on the structure of the inversion still received little attention because of previous exploration drilling focused on the target reservoir is shallow marine post-rift sediments on the limestone Peutu Formation and sandstone Baong Formation. Research on syn-rift sediments and structure inversion obtained by conducting seismic interpretation of the data from 2D marine multi-client seismic surveys with a long streamer through the Andaman Sea and surrounding areas. Several deep-water drilling exploratory wells are used as data for analysis of petroleum systems and types of hydrocarbons in the syn-rift sequence. Based on seismic data and analyzed petroleum system is generated the trapping mechanism of hydrocarbon in syn-rift sediments as resulted of tectonic inversion. Based on mapping the isopach on syn-rift sequence and seismic horizon flattening on top syn-rift can be interpreted that there are two patterns of syn-rift that developed in this area. The first is North-South trending rift developed in the South and North study area, while the second is Southwest-Northeast trending rift developing in the Central area. From observation we can conclude that the formation of rift systems in this area is controlled by major faults trending North-South trending. The faults is assumed to move horizontally to the right to form such a pattern that controls transtention rift basin. The northern part of the basin shows tectonic inversion of very large geometric pattern shown by the high relief of Harpoon-shaped structure, while the southern part shows a small inversion tectonics is indicated by the low-relief structure. Moreover, structural mapping of Top Syn-rift revealed that structural pattern of the inversion structure trending Northeast-Southwest dipping toward Sourheast. Hydrocarbons on the inversion structure can be found in the rift depocenter, as the result of Mergui-1 well which discovered gas in the Andaman Sea region of Thailand. Hydrocarbons can also be found on the rift shoulder near the bounding fault, such as drilling results JAU-1 and ITU-1 which discovered gas reservoirs in sandstone Parapat Formation. Meanwhile, wells BLD-1 did not find hydrocarbons in drilling target syn-rift sediment in area flexural margin. Based on these facts, inversion faults may be responsible for the flow of hydrocarbon migration from source rocks to sandstone Parapat Formation.