ABSTRACT

Interferometric Synthetic Aperture Radar (InSAR) measurements provide accurate, large-scale estimates of displacements within material overlying a producing reservoir. Such deformation proves useful in deducing spatial and temporal changes in reservoir fluid pressure. Starting from the pressure field we estimate the diffusive travel times, and then, as the solution of a linear inverse problem, the effective permeability of the reservoir. We incorporate inequality constraints into the inversion for volume change, under the assumption that the production only results in fluid volume decreases, and we find that the inequality constraints improve the resolution by roughly 30 to 40%. We apply the formulation to subsidence in the material overlying a thin gas production zone at the Krechba field in Algeria.

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