A Semi-Analytical Rate-Transient Analysis Model for Fractured Horizontal Well in Tight Reservoirs Under Multiphase Flow Conditions

Abstract

Rate-transient analysis (RTA) has been widely applied to extract reservoir/fracture properties using analytical and semi-analytical methods with simplifying assumptions. However, current RTA models may lead to misdiagnosis of flow regimes and incorrect estimates of reservoir/fracture information when complex fracture networks, multiphase flow, and pressure-dependent properties occur in tight reservoirs simultaneously. A semi-analytical model is developed to account for multiphase flow, complex fracture networks, and pressure-dependent properties. The technique uses the black oil formulation and butterfly model to determine three nonlinear partial differential equations (PDEs) that describe the flow of oil, gas, and water in the reservoir with a complex fracture network. A modified Boltzmann variable considering the heterogeneity of the complex fracture network is proposed to convert the fluid flow PDEs to a set of ordinary differential equations (ODEs) that can be solved through the Runge–Kutta method. A new rate-transient analysis workflow is also developed to improve flow regime identification (ID) and the accuracy of tight oil reservoirs with complex fracture networks. It is applied to a synthetic case with an equivalently modeled complex fracture network and multiphase flow. The estimated fracture properties are in excellent agreement with model inputs.