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

Abstract

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 nonlinear 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.

Prediction of immiscible gas flooding performance: a modified capacitance–resistance model and sensitivity analysis

“…7). A comparison between the M-CRM and common CRM performance was previously published in a paper by (Yousefi et al 2019). They showed improvement of using the M-CRM in immiscible gas flooding over the common CRM.…”

“…Figure 7 displays the GOR of producers in the model. The new model can be applied in pre-breakthrough and post-breakthrough conditions with acceptable results (Yousefi et al 2019). In this study, the post-breakthrough condition is chosen for interwell connectivity determination and also to predict oil production rates.…”

“…The term g,inj g which was added to the new model was developed based on consideration of variations of gas properties with pressure. Thus, this term compensates for the errors which are caused by the common CRM and is applicable in all pressure ranges (Yousefi et al 2019). Figure 9 presents cross-plots of interwell parameters for the M-CRM and SS in the history section.…”