On determination of interwell connectivity under immiscible gas injection process: Modified capacitance-resistance model

摘要

Interwell connectivity is an important parameter in reservoir management and optimization during water/gas injection. As an analytical approach, the capacitance-resistance model (CRM) is a rapid tool that only needs some common and available data for field performance prediction. The non-linear signal processing technique is used with the CRM to determine reservoir continuity between production and injection wells. Current CRMs are applicable in water flooding systems. In this study, a modified capacitance-resistance model (M-CRM) for interwell connectivity calculation in immiscible gas flooding projects is developed based on the mass balance equation. Slightly compressible flow is one of the main assumptions in CRM development while gas is compressible and the gas property variation with pressure should be scrutinized in the equations. Therefore, new equations need gas PVT properties to consider the effect of gas compressibility. Moreover, the productivity equation for oil and gas production should be revised. The constructed model that considers mass balance and the productivity equation is applied in two synthetic models and one real sector reservoir model. The genetic algorithm, as an optimization tool for solving the new model, is used and streamline simulation is selected as a validation tool for interwell connectivity parameter calculation. Based on the streamline results, it was observed that a M-CRM is able to predict the reservoir behaviour better than a common CRM for pre/post breakthrough conditions in gas injection scenarios. Also, an analysis is performed for different parameters that affect the new model in immiscible gas flooding. Results show that modification on the mass balance equation has a greater influence than the productivity equation.