Abnormal reverse faulting above a depleting reservoir

Subsurface deformation is observed during pumping of some hydrocarbon field s, Deformation features include subsidence centered on the field and subsid ence-related centripetal horizontal displacements and faulting. Focal mecha nisms yield reverse movements on steeply dipping faults. In our sand-silico ne analogue model, the reservoir is represented by a latex balloon or by un dercompacted ground sand. Deflation of the reservoir results in formation o f steeply dipping reverse faults bounding a downward-opened cone. The cone moves downward to follow the reservoir contraction. Faults along the cone a re straight beneath a thick reservoir cover and tend to curve upwards with decreasing cover. Our results, similar to natural structures observed aroun d magma chambers, allow us to reinterpret Paul Segall's numerical model of poroelastic stresses caused by changes in the distribution of pore fluids a nd draw a new pattern of active faults.