Mechanism Of Water Injection In Fractured Vuggy Carbonate Reservior

Carbonate rocks are an important class of oil and gas reservoirs, there are a large number of fractures and vugs in these reservoirs which are called fractured-vuggy carbonates. There are three types of spaces in the reservoirs, and the spaces are connected by many ways. These reservoirs are strong non-homogeneous. The relationship between oil and water in the reservoir is complex and the flow mechanism is not clear. Most of these reservoirs are developed by natural energy at present. Now many of these oil fields get into production decline period, additional energy methods such as water injection are needed to prolong the oil stabilization period. Based on the research of characteristics of fractured-vuggy carbonate reservoirs, 5 types of fractured-vuggy models were developed, including models with different vug diameter, models with different vug porosity, models with different fracture porosity, models with different fracture angle, models with different fracture network. Water injection experiments were conducted on these models. After the experiment,the feature of recovery and water cut ,the feature of pressure difference ,the feature of oil-water interface and the feature of residual oil are analyzed deeply in order to search water injection mechanism. Single-phase flow in the fractured-vuggy models were directly simulated by Navier-Stocks equation, obtained the pressure distribution and velocity distribution in the models. Navier-Stocks equation and Level Set equation were coupled to simulate the two-phase flow in fractured-vuggy models. The simulated results were compared with the experimental results to verify the correctness of the simulation method; more water injection experiments were simulated by the simulation method to find out all factors which influence the injection effect...