On the role of reservoir geometry in waterdrive hydrodynamics

The interaction of producing reservoirs with the connected waterdrive plays an important role both in planning the field production life and predicting the environmental consequences (e.g. anthropogenic land subsidence) of hydrocarbon extraction. Currently, the behavior of the system reservoir+waterdrive can be simulated with the aid of advanced numerical models, but one of the most difficult tasks is the calibration of the poorly known aquifer hydrogeological properties. In the present paper, the waterdrive hydrodynamics is simulated by a finite element flow model with the parameters calibrated so as to satisfy the material balance equation. Two field cases in the Northern Adriatic basin, Italy, are discussed, pointing out the role of reservoir geometry for a reliable simulation of the waterdrive dynamics. It is shown that quantities which are often neglected, such as the amount of water withdrawn along with the gas and the pore volume reduction experienced by the field, may be of paramount importance for the waterdrive calibration depending on the actual reservoir geometry. The results suggest that an in-depth knowledge of the reservoir geological configuration is required to accurately simulate the waterdrive hydrodynamics, and hence predict the expected amount of gas/oil withdrawn and the related anthropogenic land subsidence.