Abstract: A surfactant that changes the wettability of tight sandstone and its preparation method and application. By adding the aqueous phase solution into the oil phase solution, and under the action of the emulsifier, a uniformly dispersed phase is achieved. Then adding initiator, stirring and raising the temperature, reacting the reaction at the temperature to obtain a colorless and transparent liquid, i.e., high polymer. At room temperature, adding fluorocarbon surfactant and biosurfactant and stirring was continued for 4 hours to obtain a surfactant that changes the surface wettability of tight sandstone. The surfactant of the present invention can reduce the oil-water interfacial tension, transform the oil-wet surface into water-wet surface, which reduces the adhesion of oil droplets to rock surface and improves the flowability of crude oil in the original stratum, and improves the recovery of low-permeability reservoir.

Abstract: A method for enhancing oil recovery in huff-puff oil production of tight oil from a fractured horizontal well by an optimized reservoir pressure, washing the horizontal well by sand flushing, injecting water into the reservoir to increase the stratum pressure around the horizontal well, and stopping the water injection when the pressure retention level is 100% at end stage of the water injection period. The method for enhancing oil recovery in huff-puff oil production of tight oil from a fractured horizontal well enables the crude oil in the pores of the matrix in the tight reservoir rock developed by the natural fracture to be further recovered. Comprehensive utilization of stratum energy boost, and imbibition replacement between the injected water and the reservoir crude oil improves the single-well production to enhance the oil recovery of a tight oil reservoir.

Abstract: A surfactant that changes the wettability of tight sandstone and its preparation method and application. By adding the aqueous phase solution into the oil phase solution, and under the action of the emulsifier, a uniformly dispersed phase is achieved. Then adding initiator, stirring and raising the temperature, reacting the reaction at the temperature to obtain a colorless and transparent liquid, i.e., high polymer. At room temperature, adding fluorocarbon surfactant and biosurfactant and stirring was continued for 4 hours to obtain a surfactant that changes the surface wettability of tight sandstone. The surfactant of the present invention can reduce the oil-water interfacial tension, transform the oil-wet surface into water-wet surface, which reduces the adhesion of oil droplets to rock surface and improves the flowability of crude oil in the original stratum, and improves the recovery of low-permeability reservoir.

Abstract: A method for enhancing oil recovery in huff-puff oil production of tight oil from a fractured horizontal well by an optimized reservoir pressure, washing the horizontal well by sand flushing, injecting water into the reservoir to increase the stratum pressure around the horizontal well, and stopping the water injection when the pressure retention level is 100% at end stage of the water injection period. The method for enhancing oil recovery in huff-puff oil production of tight oil from a fractured horizontal well enables the crude oil in the pores of the matrix in the tight reservoir rock developed by the natural fracture to be further recovered. Comprehensive utilization of stratum energy boost, and imbibition replacement between the injected water and the reservoir crude oil improves the single-well production to enhance the oil recovery of a tight oil reservoir.