Coupled inverse modelling of tight CO2 reservoirs using gravity and ground deformation data.

Injection of CO2 into tight reservoirs produces both gravity change and ground deformation, which provide great opportunities for more accurate coupled inverse modelling. In this study, we incorporate signals generated from several synthetic models to estimate the CO2 distribution in the reservoir. A relationship is found that connects density variations to volumetric changes associated with injected CO2, taking advantage of a common set of model parameters for both gravitational and geo-mechanical inverse modelling. This is achieved by assuming that the injected CO2 increases pressure in the reservoir, which in turn generates extra porosity that is then filled in by the CO2 mass. Tikhonov regularization, supported by the Generalized Cross Validation (GCV) technique for finding the optimized model, is used to solve the ill-posed inverse problems. The results indicate that the uncertainty and ambiguity in gravimetric modelling due to high levels of noise is mitigated by implementing highly accurate ground deformation measurements, which normally have a higher signal to noise ratio. [ABSTRACT FROM AUTHOR]