A study of Reservoir Connectivity in the Platong Field, Pattani Basin, Gulf of Thailand

Abstract

The study area covers two development platforms, PLWD and PLWI in the Platong Field, Pattani Basin, Gulf of Thailand where the complex fluvial sand systems make it difficult to predict sand  connectivity and pressure transmission. Several wells drilled from the PLWI platform encountered high pressure sands around 1830-1890 m. TVDSS and the cause of this high pressure was  interpreted to be due to the effect from the water injection program in the PLWD platform area to the north. This study analyses and creates possible models to explain this pressure communication and the connectivity of the reservoir sands by the integration of well log analysis, seismic interpretation and formation pressure data. Two key sand systems were identified in the interval of interest; the injection sand system and the high pressure sand system. The injection sand is thick and a well defined channel system whereas the high pressure sands are more discontinuous. Many faults cut across these sand along a north-south trend making pressure transmission improbable along these stratigraphic pathways. On the other hand, pressure transmission within fault blocks is also unlikely due to the discontinuous nature of the narrow fluvial channel systems. The most likely explanation of the pressure transmission is a mix between short stratigraphic pathways within fault blocks and significant fault leakage, particularly across the smaller displacement faults. Observations from this study can be applied for future well planning in order to prevent water injection wells creating high pressure drilling hazards.