Drilling activity in the deepwater fold-thrust belt of Southeast Asia has expanded greatly and has quickly become recognized as one of the five proven deepwater oil regions in the world. Unfortunately, drilling hazards linked to pore pressure (PP)and wellbore stability problems are persistent, such that drilling costs as high as USD 100 million (as of 2014) are not uncommon. This study reviews the distinct geological nature of overpressure characteristics in the deepwater fold-thrust belt of Sundaland continental margin, SE Asia, and then subsequently presents a better PP prediction strategy that properly honors the regional characteristics.
Effective stress-based PP prediction is reviewed in depth to highlight its drawbacks. The drawbacks become especially prominent when the assumptions of the established method, particularly assumptions of the porosity-based normal compaction trend, are applied deliberately in the deepwater fold-thrust belt of Sundaland continental margin without sufficient adjustments.
It is successfully demonstrated that the absence of a normally compacted section of DTFB-SCM is linked to rapid sedimentation of low permeability sediments; tectonic shearing is the central cause of the common underestimation of the popular effective-stress based pore pressure prediction method; and the dominance of compressional geological structures explains the high likelihood of the centroid effect. Best practices are proposed as guidance for PP practitioners to steer away from blindly following industrial assumptions and carefully apply a more geologically sound PP prediction approach.
Deepwater exploration and production in SE Asia has grown rapidly and has become a major component of the petroleum industry's upstream budgets (Algar, 2012; Weimer and Pettingill, 2007). Furthermore, northwest and east Borneo is regarded as one of five proven deepwater oil regions in the world as a result of major discoveries that have taken place in the past 15 years (Weimer and Pettingill, 2007). However, many problems encountered while drilling into prospects have discouraged further development of deepwater plays despite the positive future outlook (Kirchner, 2005; Kaeng et al., 2014). In northwest Borneo in particular, operators have encountered many subsurface hazards related to PP and wellbore stability that have often led to the failure of some wells to reach geological targets and have increased drilling costs to as high as USD 100 million (as of 2014).
