A Hybrid Model for Simulating Fracturing Fluid Flowback in Tight Sandstone Gas Wells considering a Three-Dimensional Discrete Fracture

Abstract

Two-phase (gas+water) flow is quite common in tight sandstone gas reservoirs during flowback and early-time production periods. However, many analytical models are restricted to single-phase flow problems and three-dimensional fracture characteristics are seldom considered. Numerical simulations are good choices for this problem, but it is time consuming in gridding and simulating. This paper presents a comprehensive hybrid model to characterize two-phase flow behaviour and predict the production performance of a fractured tight gas well with a three-dimensional discrete fracture. In this approach, the hydraulic fracture is discretized into several panels and the transient flow equation is solved by the finite difference method numerically. A three-dimensional volumetric source function and superposition principle are deployed to capture the flow behaviour in the reservoir analytically. The transient responses are obtained by coupling the flow in the reservoir and three-dimensional discrete fracture dynamically. The accuracy and practicability of the proposed model are validated by the numerical simulation result. The results indicate that the proposed model is highly efficient and precise in simulating the gas/water two-phase flow and evaluating the early-time production performance of fractured tight sandstone gas wells considering a three-dimensional discrete fracture. The results also show that the gas production rate will be overestimated without considering the two-phase flow in the hydraulic fracture. In addition, the influences of fracture permeability, fracture half-length, and matrix permeability on production performance are significant. The gas production rate will be higher with larger fracture permeability at the early production period, but the production curves will merge after fracturing fluid flows back. A larger fracture half-length and matrix permeability can enhance the gas production rate.

Dynamic Pressure Analysis of Shale Gas Wells Considering Three-Dimensional Distribution and Properties of the Hydraulic Fracture Network

“…where p is the formation pressure, MPa; p is the average formation pressure, MPa; m is the pseudo-pressure of the formation, MPa 2 /(mPa•s); µ g is the gas viscosity, mPa•s; Z is the deviation factor; t is the time, d; and t a is the pseudo-time, d. In this paper, the three-dimensional distribution of the hydraulic fracture is considered, and the flow inside the fracture is no longer limited to one-dimensional flow as assumed in the conventional model. The flow equation in a finite-conductivity fracture is as follows [28]:…”

“…According to Equation (55), the pressure response of all fracture panels can be obtained and written in the following matrix forms: With the superposition principle, for the system in Figure 3, the pressure drop at the point (x D , y D , z D ) caused by all fracture panels can be calculated, and the equation is given by the following [28]:…”

Correlation between Natural Seepage and Ionic Diffusion in Shales

“…Process in which the two-phase flow characteristics of 3D discrete fractures cannot be calculated accurately. 17 Elputranto (2020) used the latest geomechanical nonisothermal multicomponent two-phase flow equations to simulate formation injuries during fracturing and solved the multiphysics/chemistry problem of formation injuries in the vicinity of the fracture-matrix interface. 18 However, most of the existing results are single-factor analyses, focusing on the combined flow of multiple seepage mechanisms of shale gas in the reservoir matrix and lacking the relational description of the self-absorption process and ion diffusion.…”

“…Wang (2021) integrated the finite difference method and the principle of three-dimensional volumetric source function and superposition to solve the problem of three-dimensional discrete fracturing during the fracturing process. Process in which the two-phase flow characteristics of 3D discrete fractures cannot be calculated accurately . Elputranto (2020) used the latest geomechanical nonisothermal multicomponent two-phase flow equations to simulate formation injuries during fracturing and solved the multiphysics/chemistry problem of formation injuries in the vicinity of the fracture-matrix interface …”