Geomechanical Approach for Pore Pressure Prediction at Well Scale

The Eaton-Terzaghi concept offers an appropriate framework for pore pressure prediction under the conditions of compaction disequilibrium as major source of overpressure and constant clay rich silico-clastic lithology, provided that the normal compaction trend (NCT) is well calibrated. To deal with cases that are outside of the domain of validity of Eaton’s approach, and also to make the definition of the NCT less user or calibration dependent, Total is developing and testing a new geomechanics based approach. The proposed method takes into account the heterogeneity of the lithology by considering the clay fraction and clay types. The porosity of the clay fraction is interpreted and is used for the calculation of pore pressure to avoid the impact of the other mineralogical components on the results. A Hydro-Thermo-Mechanical (HTM) coupled model in which the sediments behave as Elasto-Visco-Plastic material simulates the combined effects of temperature gradient, burial speed and complex loading/unloading scenario such as tectonic stresses, fluid expansion and hydrocarbon generation.