Geophysical Pressure Prediction in The Presence of Multiple Pressure Mechanisms with Applications to Deep Wells
Alan R. Huffman
Fusion Petroleum Technologies Inc.
Pre-drill pressure prediction using geophysical data and methods has historically been done using very simple models and has been restricted by overly simplistic estimates of the Earth’s velocity field. The advent of the effective stress concept and the pressure prediction methods that developed from that concept led to a much-needed inclusion of fundamental physics into the art of pressure prediction. Geopressure prediction techniques have started incorporating more sophisticated velocity methods such as AVO-based phase mismatch algorithms, tomography and pre-stack inversion. These technologies allow the geophysicist to obtain higher resolution estimates of the velocity field in the subsurface that can significantly improve the results of pressure prediction. These technologies permit more robust analysis of P-wave velocities in the presence of contamination from hydrocarbon effects and non-clastic rocks that have been a problem in the past. In recent years, methods have been developed to enable robust pressure prediction in the presence of multiple pressure mechanisms including undercompaction, unloading processes (secondary pressure mechanisms) and at great depth, the onset of secondary chemical compaction. These models utilize geological and geophysical information to constrain the calibration models and the depths at which they must be applied to develop a multi-layer pressure calibration model that will accurately predict pressures for prospect-level analysis and pre-drill prediction. These models are then integrated with the velocity field and the geological and geophysical information to predict pore pressures and fracture pressures at greater depths than have been previously feasible. This methodology has been tested in multiple basins and has been proven to be effective in helping drilling engineers improve well performance through more effective mud and casing program designs that significantly reduces well costs and rig time. The methodology also provides a greatly improved feedback loop for basin modeling as it can predict reasonably accurately the current pressure regimes in the subsurface under a wide range of physical conditions that can be used as an end-constraint on basin models.
AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands