Production Forecast after Hydraulic Fracturing in Naturally Fractured Reservoirs: Coupling a Complex Fracturing Simulator and a Semi-Analytical Production Model

Abstract

Abstract The growing interest in exploiting shale resources is generating new technologies in fracture modeling and reservoir simulation. In the presence of pre-existing natural fractures, hydraulic fracture propagation and proppant distribution can be very complex. Developing the tools to understand fracture propagation and its link to production in shale reservoirs is one of the major technological challenges that the industry is facing today. These challenges are being addressed with new hydraulic fracture simulators and production models for complex hydraulic fracture networks in shale reservoirs. However, the coupling between these two technologies is not mature yet. This paper presents a simple automated workflow from simulating hydraulic fracture propagation in naturally fractured reservoirs to the subsequent production. This work documents the coupling of an existing complex fracturing simulator with a new production model. The complex fracture model considers interactions with natural fractures, stress shadow effects and proppant placement. The production model is based on a semi-analytical approach applied to the discrete hydraulic fracture network. The analytical solution used to simulate the flow from the matrix into the fracture network is simple and well known, but it relies on the assumption of constant pressure in the fracture which can only be obtained with infinite fracture conductivity. An original feature of this model is an algorithm to extend the validity of the analytical solution to all fracture conductivities, by calculating a local "time delay" based on mass balance. The validity of this approach is illustrated by a comparison with results from a standard reservoir simulator. The simple automated workflow that combines the two simulators gives the opportunity to investigate the relation between production and fracture treatment design in naturally fractured reservoirs. This paper illustrates the application of the workflow to realistic cases and the sensitivity of several design parameters that affect well performance.