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.

A novel colloidal dispersion gel (CDG) was synthesized by cross-linking polysaccharide-based hyperbranched polymer (SMHBP) with aluminum citrate. Four factors affecting gelation properties were investigated including SMHBP concentration, the weight ratio of polymer to cross-linker, NaCl concentration, and additive concentration. Environmental scanning electron microscope (ESEM) was used to observe the morphologies of the CDG to understand the cross-linked mechanism. The CDG is cross-linked by both intramolecular and intermolecular, and the formation of the CDG is dominated by the intramolecular cross-linking reaction. Core displacement experiments demonstrated that the novel CDG obtained excellent profile modification performances at a high temperature and high salinity.