Water injection huff-puff oil extraction method for low-porosity ultra-low-permeability oil reservoir

The invention relates to a water injection huff-puff oil extraction method for a low-porosity ultra-low-permeability reservoir, and belongs to the field of oilfield exploitation. The water injection huff-puff oil extraction method for the low-porosity ultra-low-permeability reservoir comprises the following steps that (1) a surfactant solution is injected into a stratum; the injection displacement of the surfactant solution is not less than the critical injection displacement for fracturing the stratum; (2) soaking; and (3) well opening and suction production. According to the water injection huff and puff oil extraction method for the low-porosity and ultra-low-permeability reservoir, the problems that an oil-water well network of the low-porosity and ultra-low-permeability reservoir is incomplete, poor in physical property and low in natural productivity are solved, the reservoir pressure can be effectively increased, oil-water distribution in the reservoir is changed, crude oil in small pores is replaced i