Impact of gas production rate on water invasion dynamics in carbonate gas reservoirs with varying storage spaceson: A case study of the Sinian Dengying Formation in the Sichuan Basin

This study explores the relationship between gas recovery and water invasion dynamics in carbonate gas reservoirs with varying storage spaces to achieve their efficient exploitation. Using physical simulation experiments on vuggy, fractured, and fractured-vuggy carbonate rock samples taken from gas reservoirs in the Sinian Dengying Formation, Sichuan Basin, we comparatively analyze the water invasion dynamics of these reservoirs, and propose a novel equation for predicting water invasion dynamics: ω = AR^B. The results indicate that the proposed method is highly effective in predicting water invasion in rock samples with different 3D storage space structures, and applicable for both heterogeneous gas reservoirs with bottom water and carbonate gas reservoirs. Furthermore, it provides encouraging prediction results of apparent relative pressure and fitted water invasion volume for both vuggy cores with strong homogeneity and fracturedvuggy cores with extreme heterogeneity. Under identical experimental conditions, carbonate gas reservoirs with varying degrees of heterogeneity exhibit distinct variation in coefficient A (related to gas production rate) and constant B (associated with water invasion intensity) values. For the cores of carbonate gas reservoirs, the extent and connectivity of pores are positively correlated with the producing reserves through water drive. Higer reservoir heterogeneity is associated with a more significant reduction in formation energy and a steeper decline in actual apparent relative pressure during the late stage of reservoir exploitation. Notably, among the tested cores, water body energy produces the least impact on the experimental results of the vuggy cores compared to the fractured and fractured-vuggy cores.