ANALISIS CADANGAN HIDROKARBON BERDASARKAN DATA SEISMIK 2D PADA RESERVOIR "F" MARKER DAN "G" MARKER LAPANGAN "NAKULA" FORMASI PUCANGAN CEKUNGAN JAWA TIMUR

Abstract

A "Nakula" Field is the exploration area of hydrocarbons are located in the Brantas Block of East Java basin. Exploration target in this area are on F and G marker of Pucangan Formation with the contention that there is hydrocarbons contents in this area, especially oil. The 2D seismic interpretation and analysis of petroleum system in the research area is useful to know the types of hydrocarbons traps, litologi of reservoir, the structure direction, environmental deposition, and the area that contains hydrocarbons so that can be known the total oil reserves initially in place and the number of recoverable oil. Research method used is descriptively method with the searching F marker and G marker horizons using a interpretation software to the nine seismic sections which have tied to the wells data. While the analysis method that used was the calculation analysis of hydrocarbons reserves after plooting the OWC (Oil Water Contact) values on depth contours map of F marker and G marker. Petroleum System in the research areas, namely hydrocarbons with the source rock of shale Ngimbang Formation which had migrated toward carbonat reef of Porong and migrates back to the vulkaniclastic sandstone which is the reservoir of Zone F and Zone G. The material source of the reservoir come from sedimented magmatic resulted by volcanic erosion of Arjuno and Welirang Mountain in the southern part and then transported to the environmental transition, especially in the delta front section to the superficial sea in the inner neritic section. This is also strengthened with the foraminifera assemblages of Asterorotalia trispinosa, Asterorotalia gaimardii, Pseudorotalia schroeteriana, Pseudorotalia indopacifica, Nonion boueanum, Elphidium spp, Ammonia beccarii, and Quinqueloculina spp in the sedimentation taken in F and G marker. Hydrocarbons trapped in the antiklin structure snare which is a row of antiklinorium on Zone Kendeng with axis relatively on West-East direction and formed at Pliosen until Pleistosen periods. Resource reserves calculation was done using the volumetric method and resulted amount of Oil Initially in Place of F marker is 14.02 MMSTB and the amount of recoverable oil is 5.6 MMSTB. While in G marker has 11.93 MMSTB Oil Initially in Place and 4.77 MMSTB recoverable oil.