Well Test Analysis for Oil-Water Two-Phase Flow in Volume-Fractured Horizontal Wells

Abstract

Volumetric fracturing is crucial for developing low-permeability, tight reservoirs and unconventional formations, as its complex fracture networks greatly enhance reservoir flow capacity. However, oil-water two-phase flow in volumetrically fractured horizontal wells exhibits complex behaviors that traditional single-phase flow models fail to capture, reducing the accuracy of well test interpretations. To overcome this limitation, this study develops physical and mathematical models for oil-water two-phase flow by integrating two-phase flow theory with the fracture network characteristics of volumetrically fractured horizontal wells. Bottomhole pressure and pressure derivatives are obtained using Laplace transforms and the Stehfest numerical inversion method. Model validation against Eclipse numerical simulations and field well test data demonstrates high accuracy and reliability. Moreover, analysis of the well test curve identifies four characteristic flow regimes-fracture linear flow, fracture pseudo-radial flow, formation linear flow, and formation pseudo-radial flow-offering theoretical insights and technical support for understanding reservoir dynamics and optimizing development strategies.