Complex-Structured Reservoir Modeling On Dynamically Adaptive PEBI-Grids

Abstract

Summary The paper considers generation and application of dynamically adaptive unstructured PEBI-grids for adequate multiphase flow modeling of complex-structured reservoirs exploited by horizontal and deviated wells, including wells with single or multistage hydraulic fractures. We developed methods for constructing PEBI-grids which are more detailed near the reservoir structural features (wells, natural faults, hydraulic fractures and reservoir boundaries) and sparse away from them. These grids make it possible to increase the accuracy of flow treatment in the vicinity of operational objects, without significant slowing down of the entire calculation. A number of algorithms for constructing the PEBI-grid are developed to account for non-vertical geological faults with a complex structure (normal fault, reverse fault), the real geometry of hydraulic fracturing and hydraulically connected natural fractures obtained from a geomechanical simulator. On grids under consideration, three-phase flow problem, accounting for gravitational, viscous and capillary forces and phase transition of hydrocarbon components is solved numerically. Within the framework of the paper, the approach of the direct calculation of the inflow to and the flow inside hydraulic fractures is developed and implemented. Two-point flux approximation and mimetic finite difference are used for solving three-phase flow problem. We developed the algorithm of local grid rearrangement due to newly opened wells and hydraulic fractures growth (including waterflood-induced fracturing) that reduces simulation time. Results of calculations showing the speed, accuracy and physical adequacy of the proposed approach to the reservoir modeling of complex-structured reservoirs are presented.