Distribution patterns of waterflooded oil and gas distribution in carbonate reservoirs based on a triple porosity model.

This article focuses on developing a triple porosity numerical model for weakly volatile fracture-pore type carbonate reservoirs by dividing the reservoir into fractures, large pores, and small pores based on pore size distribution. The model integrates permeability, capillary pressure, and relative permeability calculations for each medium to simulate three-phase flow and fluid migration under various development strategies, including depletion and water injection. Results indicate that during depletion, oil primarily drains from large pores while residual oil remains trapped in small pores, and that earlier water injection improves pressure maintenance and oil recovery. Additionally, different water injection methods—steady, periodic, and asynchronous injection–production—were compared, showing that asynchronous injection–production better maintains reservoir pressure, reduces gas breakthrough, enhances capillary absorption, and improves oil recovery, especially in reservoirs with well-developed small pores. These findings provide theoretical support for optimizing development and enhanced recovery strategies in heterogeneous carbonate reservoirs.