LAUSR

ABSTRACT The natural gas can improve the flooding effect as its excellent flow property and dissolution ability, but it is also easily to form the serious gas channelling when injecting gas continuously. In order to decribe the advantages and disadvantages of natural gas flooding, the oil dispalcement experiments of injecting natural gas after water flooding with different permeability cores are done. The natural gas channelling and its prevention manner are discussed by theoretical and experimental analysis, and the water alternating natural gas (WAG) injection is introduced. The results show that the natural gas flooding can enhance oil recovery after water flooding in different permeability reservoirs, especially in lower permeability reservoirs. The continuously natural gas flooding can easily form and develop the gas channeling. It takes only 0.13 PV to 0.45 PV natural gas injection to form the gas channelling, and spends 0.5 PV to 1.5 PV injection to develop the gas channelling for making the gas-liquid ratio reaching to 200 in the cores with the permeability from 6.876 × 10−3μm2 to 540.124 × 10−3μm2 . The WAG injection with the WAG cycle below 2 can prevent the natural gas channelling and keep the good natural gas utilisation in low/ultra-low permeability reservoirs.