Pore Pressure Prediction and Distribution in Arthit Field, North Malay Basin, Gulf of Thailand

Abstract

One of the major challenges in drilling wells for the exploration and development of hydrocarbon reservoirs is to understand the variability and distribution of fluid pressure in the subsurface. In Arthit field, North Malay Basin, Gulf of Thailand, 18 exploration wells and 2D seismic which cover the overpressure zones were used to investigate pore pressure prediction methods and the distribution of overpressure in Block 15A and 16A. Sonic and density logs were used to estimate shale porosity as a tool to evaluate and observe abnormal pressure or overpressured intervals. The resistivity and sonic logs were able to recognize with good response these overpressured intervals by plotting of both logs with true vertical depth. The Eaton method was used to calculate pore pressure using sonic and resistivity logs. These results were compared with directly measured formation pressure (SRFT). The estimated pore pressure from sonic log data is better than computed from resistivity log.  The overpressure distributions mainly increase from north-west to south-east in the 2C unit and north to south with minor north-west to south-east direction in the deeper 2B and 2A units in Arthit field.