Evaluation of production losses from unconventional shale reservoirs

The Promising production trends and predictions, as well as improvements in hydraulic fracturing and horizontal drilling technologies, have made unconventional reservoirs economically feasible. Although these reservoirs have high initial production rates, it is observed that their production performance declines fast. Therefore, it is necessary to identify the reasons behind the production performance reduction. With continuing production, pore pressure decreases and consequently the effective stress applying on fractures increases. This phenomenon causes the fracture closure. In this paper, both individual and combined effects of natural fracture and hydraulic fracture closures on well performance are investigated. We use available experimental data to represent hydraulic and natural fracture conductivity alterations with changing stress conditions. Simulation results show that the individual effects of hydraulic and natural fracture closure on production performance is in the range of 6%-13% and 7%-23%, respectively. Additionally, the combined effect of natural and hydraulic fracture closure is in the range of 10%-25%. It is observed that the coupled effect of natural and hydraulic fracture conductivity losses is less than the summation of the individual effects. Sensitivity analysis is also performed for certain reservoir parameters. This work can provide a better understanding of the main reasons of production losses from unconventional reservoir simulations. (C) 2015 Elsevier B.V. All rights reserved.