A method for enhancing recovery by foam flooding assisted nitrogen huff and puff in fault-block reservoirs

Abstract

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.

Description

technical field [0001] The invention relates to a method for improving oil recovery by assisting nitrogen huff and puff by foam flooding in fault-block oil reservoirs, and belongs to the technical field of oil and gas field development engineering. Background technique [0002] Fault block reservoir refers to the accumulation of oil and gas in traps formed by fault blocking. Fault blocks are often divided and disconnected from each other. The oil-bearing area and reserves of a single fault block reservoir are low, and complex injection and production wells cannot be established. network. Some fault-block oil reservoirs have only one injection well and one production well, which is the "one injection and one production" development mode, showing the characteristics of low recovery; The water content of the produced fluid is high; some fault-block reservoirs have formation dips, and the remaining oil after water flooding is distributed in the structural high parts, forming "l...

AI Technical Summary

Problems solved by technology

[0007] (1) The generation of foam on the ground is good, but under harsh reservoir conditions, the foam stability becomes worse and the half-life is greatly reduced, so the foam lasts for a short time

[0008] (2) During the flow process of the foam in the porous medium condition of the formation, the foam cannot enter the deep part of the formation due to the shear action, and the distance of the foam action is relatively short

[0009] (3) The performance of the foam near the injection well is good. During the displacement process, the surfactant in the foam liquid is gradually absorbed by the formation. After long-distance migration, the concentration of the surfactant decreases, and the burst foam cannot be regenerated

[0011] (1) With the increase of the huff and puff cycle, nitrogen tends to form a large continuous channel in the formation, and the phenomenon of gas channeling is serious during the mining process, and nitrogen cannot form an effective residence in the formation

[0012] (2) With the progress of throughput, the amount of movable oil within the effective range of throughput is getting less and less, the degree of periodic recovery is getting lower and lower, and the effect of throughput is no longer ideal

[0013] (3) In the later stage of huffing and puffing, with the increase of the produced liquid volume, the ground pressure decreases greatly, and the formation energy is in short supply, and the formation energy cannot be effectively replenished only by nitrogen injection.

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