Estimating Formation Pore Pressure in Tectonic Compression Zones

摘要

Accurate knowledge of formation pore pressure is a key requirement for safe and cost-effective drilling in overpressured formations. Tectonic compression is an important type of overpressure mechanism, in addition to undercompaction and fluid expansion. However, there is not a valid approach for overpressure estimation in tectonic compression zones. Actually, two lateral stresses are too large to be ignored in tectonic environments. As a consequence, the conventional overpressure estimation methods are not accurate enough for tectonic compression mechanism. This article presents a new approach called the root mean square (RMS) principal stress method that modifies the estimation of pore pressure for tectonic compression zones. The RMS method better considers the characteristics of a 3D stress state. It has been tested in the Kuqa thrust belt of Tarim oilfield where significant tectonic compression commonly exists. Pore pressure estimation of this region shows that the RMS method provides more precise pore pressure estimates than conventional methods.