Integrating the Fully Coupled Geomechanical with Thermodynamics Modeling for Accurate Pore Pressure Prediction - A Case Study from China

Abstract

Abstract The accurate prediction of pore pressure relates directly to various important affects oil and gas field exploration and development including drilling engineering design and formulation of oil and gas reservoir development plans. The well logging information with unique advantages such as high vertical resolution and capability of continuous measurement has been widely used in formation pore pressure prediction. Currently, though the industry has developed many methods for formation pore pressure well logging prediction, they may not be all used to calculate formation pore pressure in actual production. And it may be difficult to guarantee the prediction accuracy with a single method. In order to accurately predict formation pore pressure, this paper systematically reviewed domestic and foreign literatures on formation pore pressure well logging prediction, explained the methods and principles of each prediction technique in detail, and summarized the applicability of each formation pore pressure prediction technique in detail. This paper concluded that both the effective stress method and the Bowers method could be used to accurately predict the formation pore pressure, and the empirical statistical model method also had high prediction accuracy, while the equivalent depth method and the Eaton method which are subject to the accuracy of the normal compaction trend equation had relatively poor prediction effect. It will be a trend in this field to construct the formation pore pressure nonlinear prediction model based on mechanical parameter tests in the study area with organically integrating geophysical well logging and pressure detection data. The study area is located southwestern China, the deep formations that more than 4000 meters are high temperature (150-180 deg C). Thermal-related secondary pore pressure generating mechanism may become active leading to higher overpressure and difficulties in prediction. For the case study, an empirical relationship of overpressure impact factors versus temperature of shale was proposed. An accurate pore pressure model generated using available well-scale geomechanical model and overpressure impact factors. With an integrating fully coupled PPP model as foundation, the integrated approach helps deep wells to reduce serious wellbore instability caused by abnormal formation pressure, wellbore collapse and other complex drilling problems.