Abstract
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.
Highlights
Hydraulic fracturing technology can achieve the extraction of hydrocarbon from unconventional reservoirs at a low cost and improve the well performance significantly, which has been attracting considerable attention in recent years [1,2,3,4,5,6,7]
We investigate the influences of fracture permeability, fracture half-length, and matrix permeability on rate transient behaviour
The main conclusions of this work are as follows: (i) Comparable reservoir simulator results reveal that our proposed model can be used to model gas and water flowback behaviour and early-time production performance of the three-dimensional fracture with satisfying precision and high computation efficiency (ii) The fracture permeability, fracture half-length, and matrix permeability can significantly influence the rate transient behaviour
Summary
Hydraulic fracturing technology can achieve the extraction of hydrocarbon from unconventional reservoirs at a low cost and improve the well performance significantly, which has been attracting considerable attention in recent years [1,2,3,4,5,6,7]. The two-phase (gas + water) flow in the hydraulic fracture is quite common during the flowback and early-time production periods [9,10,11,12]. A common challenge for tight sandstone gas reservoir evaluation is the characterizations of the threedimensional fracture. The productivity prediction of tight gas wells is greatly affected by the characteristics of the gas-water two-phase flow and fracture seepage parameters. Much research has been dedicated to theoretical models of fractured tight gas wells [13,14,15,16], but most are only applicable to single-phase flow problems. The threedimensional fracture characteristics is seldom considered in these models
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