A method for improving oil
recovery by using foam flooding assisting
nitrogen soaking in a
fault block oil reservoir comprises the steps that a developed reservoir is selected;
injection well preformed foam injection is performed; production well
nitrogen injection is performed; shut-in well oil-gas gravity differentiation is performed; and a production well is opened for production. By the adoption of the method, the property that the foam blocks the large and does not block small and blocks water and does not block oil is used, that is, the property that under the general condition, the foamhas the tendency to block pore passages with the larger permeability and pore passages with the higher oil saturation in the stratum is used, the swept volume of the foam near an
injection well is expanded, and the problem of less movable oil in the
late stage of huff and puff of the production well is alleviated to a certain degree. By the adoption of the method, the vertical fluctuation of thenitrogen can be strengthened when the
nitrogen is injected into the production well, the longitudinal action
radius of the nitrogen huff and puff can be expanded, and meanwhile the problem that the foam flooding is difficult to be effective near the production well is effectively alleviated due to the effect introduction during the huff and puff processes; and the foam flooding assisting can improve the effective cycle of nitrogen huff and puff, the
recovery of nitrogen huff and puff is enhanced, and the development of
fault block reservoirs is further improved.