Characteristic of Pore Pressure at the Sub Surface Sedimentary Rock in Deep Water Part of Kutai Basin, East Kalimantan, Indonesia

The Kutai Basin is the biggest Tertiary basin in Eastern part of Indonesia, contains a significant amount of hydrocarbon accumulation, proven by the discovery of giant oil and gas fields. Currently, the majority of hydrocarbon exploration activities in Kutai basin is still concentrated on onshore, shelf, and Mahakam delta. Drilling activities at deep water part of Kutai basin is still slow due to high cost and limited of geological data information regarding to the petroleum system and geopressure of this part of the basin. In hydrocarbon exploration, information about geopressure within a basin is very important. For a geologist, information about subsurface geopressure is useful to look at the maturity and the migration of hydrocarbon in a basin. For a petroleum engineer, the subsurface geopressure information is useful to manage the production rate of hidrocarbon from the well. For a drilling engineer, this information is useful to design the type and density of drilling mud weigh and also casing pipe that will be used to prevent a blowout. In this research, the geopressure study at the deep water part of Kutai basin, particularly along Makassar Strait as of recent condition has been done. The objective of the research is to study the characteristics, vertical distribution, and the cause of overpressure within the area by using integration of geological and geophysical data. . The research shows that in this area exists four main geopressure zones vertically. According to its depth, they are normal hydrostatic pressure occuring at a normal compaction where sedimentary rock layer lies, continue by abnormal pressure due to disequilibrium compaction, clay mineral diagenesis, and at the deeper section was expected by hydrocarbon generation.