Joint inversion of production data and subsidence measurements

In order to get the maximum yield of a hydrocarbon reservoir, it is necessary to get the best insight in the properties of the reservoir. This insight is corroborated by measurements obtained during the lifetime of the reservoir, the main measurements being the pressures and flow rates of the producing wells. At the same time, surface subsidence is a commonly occurring phenomenon associated with the production of hydrocarbons. We have integrated the use of subsidence measurements with the use of pressure and rate measurements in an EnKF assimilation procedure to improve the knowledge of the permeability field in an oil or gas reservoir. We have applied this procedure to a virtual reservoir, using a synthetic reservoir model that had been developed in other EnKF studies. With the same geologic input as for the synthetic "truth", en ensemble of 100 realizations of the permeability field was created. The "truth" reservoir was used to create both pressure and rate and subsidence measurements. The measurements were perturbed to create a representative set, and this set was used as data input in the EnKF method to assimilate the properties of the members of the ensemble. We observed that the assimilated ensemble gave better predictions when the subsidence data were incorporated as additional measurements, especially in later stages of the production when the subsidence levels became larger. Furthermore, the procedure promotes better insight in the compaction process of reservoirs. This can help to predict subsidence at vulnerable areas such as the Netherlands.