Method for improving oil-water displacement recovery ratio of low-permeable oil reservoir

The invention relates to a method for improving the oil-water displacement recovery ratio of a low-permeable oil reservoir, which comprises the following steps of: preparing a mixed aqueous solution containing 400-4000mg/L of surfactant and 200-2000mg/L of foam stabilizer from the surfactant, the foam stabilizer and water; and mixing the mixed aqueous solution and a gas according to a volume ratio of the solution to the gas of 1: (0.1-2), and injecting into the oil reservoir through a water injection well, wherein the injection time is 90-120 days. The surfactant is selected from one or two of branched sodium alkybenzenesulfonate, alkyl polyoxyethylene ether sodium sulfate, alkyl polyoxyethylene ether sodium carboxylate, fatty alcohol ether sodium sulfate and cocoamido propyl hydroxy sulfobetaine; the foam stabilizer is sodium carboxymethylcellulose; and the gas is air. According to the invention, after the water content of the extracted solution reaches 60 percent, the oil displacement efficiency is improved