Gas-Water Composite Flooding Technology for Fractured and Vuggy Carbonate Reservoirs in Tahe Oilfield

After water flooding, a large amount of “attic oil” will be left in the structural top of fractured and vuggy carbonate reservoirs in the Tahe Oilfield. Due to weak lateral drives, a large amount of remaining oil will be accumulated between wells even with nitrogen flooding. According to the reservoir characteristics and remaining oil distribution features of such reservoirs, a gas-water composite flooding technology was studied. Based on the analysis of gas-water composite flooding mechanisms, different gas-water composite flooding development modes have been established according to the distribution features of remaining oil. Based on the characteristics of inter-well communication pathways, the development well pattern was designed taking into consideration the unique conditions, and gas-water composite flooding parameters were designed from historical water flooding data and the cumulative gas injection volume. The gas-water composite flooding technology was applied in 7 injection-production well group of Block 4 of the Tahe Oilfield, and the oil production of this well group was increased by 80.0 tons on average. The results indicate that gas flooding in the gas-water composite flooding drives the “attic oil” to the water flooding channel first, and then the water flooding provides lateral driving force to transport it out.