Overpressure Prediction Challenges in Deepwater Sundaland

Abstract

Overpressure presents major challenges in deepwater drilling in Southeast Asia. It effects primary well-design factors, such as the number of casing strings, mudweight used during drilling, and cementing programs, which are critical in minimizing subsurface hazard and non-productive time (NPT) as a result of kick, loss of circulation, and wellbore stability. Southeast Asia's sundaland geological region is the home of overpressurized sedimentary basins, mainly owing to the relatively young and active tectonics, rapid sedimentation, and the relatively ‘warm’ (i.e. high heat flow) conditions in the basins. The study confirmes that Sundaland continental margin deepwater environments have distinctive overpressure characteristics from those of shelfal and onshore environments, which could be related to compaction history, depositional facies, and structural styles of the region. They present some unique challenges in pore pressure prediction and well design. This environments, characterized by thick water columns, fine-grained sediment domination, and low-permeability systems, cause the overpressure to be shallow and continuous, running relatively parallel with effective stress. The presence of deepwater thrust-fold belts in major basins, as caused by gravity-driven and basement-driven shortening, also contributes to the region's charactirstic. These compressional forces impact the compaction characteristic further and introduce common geopressure centroid phenomena, which in some cases have caused some serious drilling problems and failure to reach drilling targets.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015