A poroelastic reservoir model for predicting subsidence and mapping subsurface pressure fronts

A forward model was constructed to numerically predict surface subsidence a nd reservoir compaction following the approach of Segall [Pure Appl. Phys. 139 (1992) 536]. A nucleus of poroelastic strain is numerically integrated over a rectangular prism assuming constant pressure change. This fundamenta l geometry allows a reservoir to be divided into many small cubic blocks in a manner similar to reservoir simulation. The subsidence and compaction ef fects of the pressure chan-e throughout the reservoir are calculated by the superposition of results from each individual block. Using forward modelin g, pressure boundary conditions can be acquired from pressure test data or reservoir simulation predictions. An inversion model also was developed tha t can track pressure fronts in a subsurface reservoir using surface displac ements. The capability of the inversion model was demonstrated using synthe tic examples of one-well and four-well cases with different layouts of surf ace observation locations. The impact of noise on the inversion result is a lso included. (C) 2001 Elsevier Science B.V. All rights reserved.