Abstract: Abnormal Pressure Study in the Malay and Penyu Basins: A Regional Understanding

Mohd Shariff Kader, Warren Leslie

A majority of wells drilled in the Malay and Penyu basins were terminated due to abnormal pressure. Blowouts and the subsequent loss of technical data have always been a concern during drilling operations.

This study employs data from 94 exploratory wells spread throughout the Malay and Penyu basins. The postdrill abnormal pressure predictive method used is pressure vs. depth plots of data obtained from Repeat Formation Tester (RFT) readings. The study results indicate that abnormal pressure occurs in a progressively older stratigraphic unit toward the basin margins. The margins of the Malay and the entire Penyu basins tend to be normally pressured. The onset of abnormal pressure appears to be abrupt in the northern portion and more gradual in the southern part of

the Malay Basin. Abnormal pressure in the Malay Basin is found to be neither depth dependent nor age related.

Many factors can cause the abnormal formation pressures. In some areas, a combination of factors prevails. Rapid deposition of the middle to late Miocene siliciclastic sediments appears to be a dominant cause particularly in the center of the Malay Basin. A low sand:shale ratio coupled with a high geothermal gradient is also found to be a local cause near the axis of the basin. This phenomenon is crucial to the understanding of the hydrocarbon migration and will enable the planning of safe and efficient drilling campaigns.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994