Polymer microsphere/endogenous microbial/biological surfactant ternary composite flooding type method for improving crude oil recovery efficiency of low-permeability oil reservoir

Abstract

The invention relates to a polymer microsphere/endogenous microbial/biological surfactant ternary composite flooding type method for improving the crude oil recovery efficiency of a low-permeability oil reservoir. The coordination of the polymer microsphere profile control, the endogenous microbial flooding of the reservoir and the biological surface active agent displacement technology is realized for the first time and can be applied to crude oil exploitation of fractured sandstone reservoirs at the reservoir temperature of 30 to 55 DEG C and the reservoir permeability less than 50*10~3micron<2>. With a composite slug profile controlling and flooding method, the slug combination includes a low-concentration polymer microsphere solution of 0.05 to 0.1 PV, a high-concentration polymer microsphere solution of 0.4 to 0.6 PV, formation water of 0.01 to 0.02 PV, and an endogenous microbial activator of 0.4 to 0.6PV. A core is closed and then culturing is carried out for 10d at a reservoirtemperature; a biological surface active agent solution of 0.1 to 0.2PV is injected, so that a composite reservoir oil displacement system and residual oil are in full contact and the oil is displacedfully. The water flooding efficiency is increased by 26.2%; the effect is obvious; and the concept and need of green and high-efficiency development of all large oil fields are met.

Description

technical field [0001] The invention belongs to the technical field of tertiary oil recovery, and in particular relates to a method for improving the oil recovery rate of low-permeability oil reservoirs by polymer microsphere / endogenous microorganism / biosurfactant triple compound flooding. Background technique [0002] Traditional tertiary oil recovery technology usually focuses on single oil displacement performance, especially chemical surfactant oil displacement technology emphasizes how to achieve the performance index of reducing oil-water interfacial tension, and often neglects the performance of crude oil emulsification and improvement of rock wettability. At the same time, the chemical surfactant flooding technology still has application limitations such as high operating costs and difficult treatment of produced fluids. When microbial oil displacement is carried out alone, although multiple oil displacement mechanisms can be exerted at the same time, the cost is low...

AI Technical Summary

Problems solved by technology

At the same time, the chemical surfactant flooding technology still has application limitations such as high operating costs and difficult treatment of produced fluids.

When microbial oil displacement is carried out alone, although multiple oil displacement mechanisms can be exerted at the same time, the cost is low, and it is environmentally friendly, but its effective time is short and the oil displacement effect is not ideal

In addition, these two flooding methods still have the problem of low sweep coefficient when applied to reservoirs with low permeability fractures.

Although polymer flooding has achieved good results in the application of medium and high permeability reservoirs, studies have shown that when the physical properties of the polymer and the oil layer are relatively stable, the relative molecular weight of the polymer in the low permeability oil layer has a linear relationship with the permeability, and the permeability When the ratio of the square root of the rate to the radius of gyration of the polymer molecule is less than 1.5, the oil reservoir will be blocked, but the lower the relative molecular weight of the polymer, the worse the oil displacement effect

In addition, low-permeability reservoirs have small throats and complex pore structures, while polymer molecules have a large radius of gyration and high viscosity, making it difficult to effectively inject into the reservoir, resulting in the inability to effectively improve the water flooding recovery of low-permeability reservoirs

Due to the problems of inorganic alkali surface scaling and reservoir damage, the application of ASP flooding technology in low permeability reservoirs is also limited

However, this invention has the following disadvantages: (1) fractures in low-permeability reservoirs are developed, and polymer system slugs are not provided before and after the injection of endogenous microbial activators. Before the bacteria are fully contacted, the injected activator is likely to have entered the fractures and large pores, and activator channeling occurs, which reduces the activation effectiveness of endogenous microorganisms and the oil displacement effect of endogenous microorganisms, resulting in the loss and waste of activators

(2) Under normal circumstances, the yield and viscosity of polymers produced by microbial fermentation are low, and it is difficult to achieve the ideal plugging strength only by activating endogenous polymer-producing bacteria to play a role in plugging regulation, so other profile control technologies must be supplemented

[0004] In view of the application limitations of traditional binary and ASP flooding technologies in low-permeability reservoirs, and they are not environmentally friendly, and the single endogenous microbial flooding technology cannot effectively seal the fractures and large pores of low-permeability reservoirs, it is easy to cause Waste of activator, reducing the oil displacement effect of endogenous microorganisms, etc.

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