A novel semi-analytical model for pressure transient analysis of fault-controlled fractured-caved gas reservoirs and field applications

Fractured-caved gas reservoirs are widely distributed and hold substantial reserves in northwestern China, showing considerable development potential. However, their strong heterogeneity and significant variations present challenges. Conventional multi-media well test interpretation models are not well-suited to fractured-caved gas reservoirs, while more suitable numerical models often require lengthy modeling times and extensive computations. To address these limitations, this paper introduces an efficient semi-analytical well test interpretation model adaptable to various fracture–cave combinations. This model integrates methods such as fluid flow and storage flow theory, the point source solution method, and multi-parameter optimization. Results demonstrate that for different wellbore–fracture–cave configurations, the point source solution method requires only the construction of a coupled solution matrix for each unit to obtain the pressure and flow rate distributions, significantly reducing the workload associated with model setup and solution. Additionally, applying the semi-analytical models to typical wells in the Shunbei field yielded strong fitting accuracy and effectively inverted key parameters related to the wellbore, fracture regions, and caves. The models developed in this paper provide valuable guidance for the efficient development of fractured-caved reservoirs.