Analysis of deformation measurements for reservoir management

Abstract

If reservoir deformation measurements can be analyzed to give consistent and coherent information on the volume changes and shear distortions taking place in the reservoir, data may be used for reservoir management and optimization of production and injection operations. Deformations may be measured at surface or at depth using a variety of technologies with different costs, ease of data collection, precision, areal coverage, and so on. The two most common techniques are the precision laser level survey, and the installation of geophysical tilt meters. Design of a suitable monitoring network for specific cases requires forward modeling using solutions that vary from spatial numerical integration of simple Green's functions to a full nonhomogeneous three-dimensional finite element model. Rigorous deformation analysis falls into two categories: direct inversion and optimization of a forward model through error minimization. Three approaches are discussed: a direct inversion based on a nucleus-of-strain formulation, a multiparameter optimization of a single source function for hydraulic fracture analysis, and a displacement discontinuity forward optimization technique using a limited population of elements. Interpretation cannot be done in isolation: other data sources, including the project history, must be integrated to maximize the utility of the deformation analyses. As a final step, the data are used to help refine mathematical stress-flow reservoir models, which in turn become better predictors of deformation as well as oil production.