The Stratigraphic Trap in the Benchamas Field Pattani Basin, Gulf of Thailand

Abstract

This research focuses on the possible key elements which define purely stratigraphic trap plays in unfaulted areas in the Pattani Basin, based on data from the Benchamas field. The analysis integrates the well logs, 3D seismic, mud log and production data to develop a model for the stratigraphic trap. Five wireline logs in unfaulted zones and nearby wells were used to define the lateral extent of the key reservoirs in the area and used to construct the initial model for possible trapping styles. Threedimensional seismic data analysis corroborated the actual trapping styles which defined the postanalysis model. Detailed interpretation determined both structural and stratigraphic traps exist in the study areas. The thin sands, which pinch-out on the structural high, tend to be  the stratigraphic traps with hydrocarbons filled full-to-base whereas the thick sands are more likely to be structural traps with hydrocarbons on water. The integration of amplitude maps and seismic character can image the channel sand distributions where the pinch-out sands are likely to be located on the channel margins, whereas the thick sands are found in the middle of the channel systems. Sequence 3 has a potential for stratigraphic trap from thin sands interbedded with thick shales. Production data reveals the reservoirs performance and shows that the pinch-out sands can be rewarding as seen by 195,000 bbl of cumulative oil  production in the BEWG-17 well. Several constructed models were defined which add value to the understanding of the stratigraphic trap mechanisms in the basin and can help to choose future well locations in the Gulf of Thailand.