Efficient production estimation for a hydraulic fractured well considering fracture closure and proppant placement effects

It is important to accurately estimate performances of a hydraulic fractured well, because it will be utilized to evaluate various completion parameters and furthermore to establish a future development plan. Shale gas reservoirs with fracture networks have high initial production rates but show drastic production decline as reservoirs are depleted by production. One of the reasons behind this phenomenon is an increased effective stress during production resulting in fracture closures. Gas mainly flows through hydraulic and natural fracture networks, so the fracture closures cause permeability reduction in the flow areas. In typical hydraulic fracturing operations, proppants are injected with fracturing fluid and placed in the fracture networks. Proppants play a crucial role to keep an induced hydraulic fracture open and retain a well productivity. However, only small portion of the fracture networks are filled with proppants (propped fracture) and the rest exist without proppants (unpropped fracture). Therefore, fracture closures of these regions are quite different. In this article, we have investigated to identify the combined effect of fracture closure and proppant placement on production estimation of a shale gas well. A numerical model has been developed to mimic well performances in Horn River Basin, BC, Canada. We have used pressure-dependent correlations based on experiments to consider fracture permeability alteration with changing reservoir pressure. Proppant placements are described using a fracture propagation model and this enables to classify a whole reservoir into sub regions such as propped, unpropped fracture, and matrix. By comparing with different cases, this article shows that reasonable results on gas production estimation are accomplished when considering fracture closure and proppant placement effects together.