Modeling Propped and Unpropped Fracture Conductivity in Fracture and Reservoir Models: Powder River Basin Turner Study

Abstract

Abstract Well spacing in unconventional fields is a challenging task because the hydraulic fracture geometry is not fully known and there is uncertainty about reservoir properties. Integrating geomechanics medeling with reservoir simulation is a cost-effective and efficient approach for generating realistic fracture geometry, estimating fracture conductivity, and understanding fluid flow behavior. This paper presents a case study of integrated geomechanical and reservoir flow simulation validated with fracture and reservoir diagnostics for the purpose of determining ideal well spacing. In a Rocky Mountain Powder River Basin field, a standalone horizontal well in the Turner reservoir was produced for almost a year before drilling adjacent infill producers. FMI logs recorded in the infill wells indicated hundreds of hydraulic fractures growing from the parent well. Based on the distances and the hydraulic fracture density from the image logs, a 3D fracture model was calibrated for the parent well. The fracture geometry and simulated proppant concentration were then exported to a reservoir simulator, where production was history matched. This simulation was constrained by measured far-field pressure data from the DFIT in each wellbore. A rigorous fracture conductivity calculation workflow was developed and applied before reservoir simulation. The conductivity workflow uses simulated proppant concentration from the fracture model and conductivity measurements of propped and unpropped fractures to define a conductivity distribution for reservoir simulation. Additionally, a proppant creep function was developed to characterize proppant-pack conductivity degradation over time. By applying the fracture conductivity calculation workflow and the measured far-field pressure constraints, the production history was matched for the full parent wellbore. The simulation results show that the parent well's drainage are covers some of the infill well's targeted reservoir. Subsequent hydraulic fracture simulations of multiple infill wells then demonstrated the effect of parent well depletion and rock stresses on the hydraulic fracture geometry of the infill wells. Our case study illustrates: (a) how modeled hydraulic fracture geometry can be calibrated using image logs recorded in the laterals of infill wells, (b) how a new proppant conductivity algorithm can be used to assign propped and unpropped fracture conductivity based on physics-based models of proppant concentration, (c) how reservoir simulation can be constrained with a calibrated fracture model and far-field pressure measurements, and (d) how a new proppant creep function can be used to describe proppant-pack conductivity degradation over time.