TERTIARY PE647-TROLEUM SYSTEM ELEMENTS OVERVIEW IN THE ONIN PENINSULA, PAPUA

摘要

Fieldwork has been conducted in the Onin Peninsula from Fak-fak to Kokas, Papua. Outcrop observation has been conducted along major road cuts. Collected samples were sent to the laboratory for biostratigraphy, petrography, and source rock analysis.The Oligo-Miocene limestone exposed in this area can be divided into two types: clastic limestone in the South and karst limestone in the North. The thickness of Oligocene shale exposed in the centre and northern part is greater than 5 meters.The outcrop located at the axis of the NW-SE Onin Peninsula anticline shows repetition of sedimentary rock outcrops running from South to North. These sections are cross cut by NW-SE and NE-SW trending faults and possibly shear fractures. Observations included NW-SE thrust faults in the grey limestone and a strike-slip system that cut the old NW-SE structure.Several shale intervals interbedded with limestone were sampled in the field and were sent to the lab for source rock quality analyses. TOC ranges from 0.33 to 1.03 %wt with Hydrogen Index (HI) ranging from 20 to 135 mgS2/g TOC. All samples are immature based on Tmax of 416 to 428 degC. Most of the shales are considered poor source rock. Only one sample showed moderate quality (TOC of 1.03% and HI of 135 mgS2/gTOC).Five outcrop samples have been taken and have been analyzed to study reservoir properties in the Onin Peninsula. Petrography analysis concluded that most of the samples are globigerinid limestones, deposited in low energy and open deep marine environments.Evaluation of the petroleum system indicates the Tertiary play in the area has poor to good source rock and poor reservoir quality. Better understanding of the regional Tertiary depositional environment may change this paradigm.