Advances in Hydromechanical Coupling for Complex Hydraulically Fractured Unconventional Reservoirs

摘要

Proper understanding of the in-situ stress conditions is essential to safe, efficient, and productive development of many unconventional resources, including shale gas and oil and coal seam gas, as well as tight sandstones and carbonates. Hydraulic fracture propagation geometry, and the geometry of both inflated and reactivated natural fractures, can be difficult to predict due to their complex interaction with the natural faults and fractures, the mechanical properties of surrounding formations, and the in-situ stress field. This paper presents a combined workflow consisting of the Discrete Fracture Network (DFN) algorithm and the Finite Element Method (FEM), which provides a three-dimensional basis for simulating the interaction between natural fracture geometry, rock mechanical properties, and the in-situ stress conditions. Furthermore, the developed framework also provides an improved basis for simulation of hydraulic fracture and reactivated natural fracture geometry, including both the interaction with the pre-existing geologic setting, and the interactions which occur between adjacent, simultaneous hydraulic fractures, or during refracturing operations. The developed workflow allows the basic natural fracture network to be geomechanically upscaled to allow prediction of the elastic rock mechanical properties as a function of both the elastic properties and the spatially varying fracture network. This work importantly demonstrates the coupled DFN-FEM simulation strategy as an efficient approach for providing detailed understanding of fracture reservoir development during stimulation.