Pressure Transient Analysis of Fractured Caved Carbonate Condensate Gas Reservoirs with Laterally Beaded Large-Scale...

Fractured caved carbonate condensate gas reservoirs (FCCCGRs) in northwestern China represent an important target for natural gas development, yet their highly heterogeneous structures and multiphase flow behaviors pose significant challenges for pressure transient analysis (PTA). Although several analytical and numerical models have been proposed for fractured caved reservoirs, they often fail to adequately capture the combined effects of condensate gas two-phase flow, laterally beaded large-scale cave geometry, and the diagnostic pressure transient features associated with multicave connectivity. To address these limitations, this study develops a novel analytical well test model for FCCCGRs with laterally beaded large-scale caves. First, the model integrates multiphase flow behavior and linearizes the governing equations through pseudopressure and pseudotime transformations. The governing equations are formulated and solved in the Laplace domain, and the corresponding solution methodology under infinite, closed, and constant pressure boundary conditions is described in detail. Subsequently, pseudopressure and derivative type curves are generated to delineate distinct flow regimes and to investigate the impacts of key parameters such as cave storage constants, fracture conductivity, mobility ratio, storage ratio, and region length on flow behavior. A major contribution of the proposed model is that it links the number and arrangement of laterally beaded caves to identifiable diagnostic features on the pressure derivative curves. Specifically, each additional cave introduces an additional concave feature in the derivative curve, providing a practical basis for cave number identification in well test interpretation. Furthermore, sensitivity analyses demonstrate that cave storage constants primarily control the depth and width of concave responses, while fracture conductivity and region length govern the duration and magnitude of linear-flow regimes. Higher mobility ratios result in delayed appearance and increased derivative responses of the corresponding linear- or boundary-flow regimes. Higher storage ratios lead to earlier termination of the corresponding cave-response regimes. Finally, the proposed model is validated using field data from a representative FCCCGR in Xinjiang, showing excellent agreement between the simulated and observed pressure responses. The interpretation results quantify cave volumes, separation distances, dynamic reserves, and production capacity, demonstrating the model's practical applicability for reservoir characterization and development planning.