Pressure transient analysis of multiple vertical fractures in a composite reservoir model

Abstract

This work developed a composite reservoir model with the inner region containing multiple hydraulic fractures and the outer region showing conventional natural fractures. Using the model, transient pressure, flow regimes and parameter sensitivities of this composite system are investigated. A vertical fractured well in this reservoir may exhibit five flow regimes: fracture linear flow, transition flow, radial flow, inter-porosity flow and pseudo-steady flow. Two characteristic V-shaped segments are observed on pressure derivative curves, one corresponding to transition flow, which may be absent at a high fracture diffusivity ratio or a low fracture conductivity ratio, and the other corresponding to inter-porosity flow. In the pseudo-steady period, the pressure and pressure derivative curves for different fracture diffusivity ratio, fracture conductivity ratio and interporosity coefficient normalise while the curves for different storativity ratio parallel to each other. In addition, regressed solution of fracture linear flow and approximate solution of pseudo-steady flow are derived in detail. [Received: August 4, 2017; Accepted: December 9, 2017]