Multi-slug surfactant combined oil displacement system suitable for low-permeability reservoir and preparation method of multi-slug surfactant combined oil displacement system

Abstract

The invention provides a multi-slug surfactant combined oil displacement system suitable for a low-permeability reservoir. The multi-slug surfactant combined oil displacement system is composed of a low-viscosity ultralow interfacial tension surfactant displacement slug and a high-viscosity ultralow interfacial tension surfactant profile control and displacement agent slug. The surfactant flooding slug with low viscosity and ultralow interfacial tension is prepared from the following components in percentage by mass: 0.2 to 0.3 percent of {bis [N-methyl-N-(3-dodecyloxy-2-hydroxyl) propyl-N-(2-hydroxy-3-sodium sulfonate) propyl] ammonium chloride} ethane, 0.1 to 0.35 percent of anionic-nonionic surfactant, 0.04 to 0.14 percent of chelating agent, 5 to 7 percent of inorganic salt and the balance of water. The high-viscosity ultralow interfacial tension surfactant profile control and flooding agent slug is prepared from the following components in percentage by mass: 0.2 to 0.3 percent of betaine type surfactant, 0.1 to 0.35 percent of nonionic surfactant, 0.02 to 0.07 percent of counter ion compound, 0.04 to 0.10 percent of viscosity stabilizer, 5 to 7 percent of inorganic salt and the balance of water. According to the surfactant combined oil displacement system, the salt resistance of the two slugs is good, the oil displacement efficiency can be remarkably improved and the sweep efficiency can be improved through multi-round alternate injection, and step-by-step integrated profile control and displacement from the immediate vicinity of a wellbore to the deep part of an oil reservoir can be achieved.

Description

technical field [0001] The invention belongs to the field of chemical flooding, and in particular relates to a multi-slug surfactant combination flooding system suitable for low-permeability oil reservoirs and a preparation method. Background technique [0002] Surfactant flooding is selected for low-permeability reservoirs. Due to the small molecular weight of surfactants, it has good shear stability in porous media, which solves the problem of difficult injection of displacement fluid in low-permeability reservoirs, and can effectively reduce wellhead injection pressure and increase injection volume. , Improve oil washing efficiency. Surfactants have been injected into low-permeability reservoirs in Yanchang Oilfield, and some effects have been achieved, but there is a risk of deactivation of surfactants due to high salinity and high calcium and magnesium ions, and it is difficult to improve the performance of low-permeability reservoirs with strong heterogeneity. Absorbe...

AI Technical Summary

Problems solved by technology

Surfactants have been injected into low-permeability reservoirs in Yanchang Oilfield, and some effects have been achieved, but there is a risk of deactivation of surfactants due to high salinity and high calcium and magnesium ions, and it is difficult to improve the performance of low-permeability reservoirs with strong heterogeneity. Water absorption profile

[0003]Low-permeability reservoirs are widely distributed in my country. These reservoirs generally have the characteristics of "low porosity, low permeability, and low production". Conventional water injection and gas injection methods are adopted It can improve the development effect of low-permeability reservoirs, but in the middle and later stages of development, "injection failure", water channeling or gas channeling are prone to occur, and the sweeping efficiency of injected fluid and oil washing efficiency are low, resulting in low production degree of low-permeability reservoirs, recovery low rate

At present, the commonly used methods are: polymer flooding, alkaline water flooding, and surfactants, but alkaline water flooding will produce precipitated substances, and at the same time increase the difficulty of processing the produced fluid; polymer flooding is difficult to inject in low-permeability reservoirs, so the surface Active agent flooding has become an important method of enhancing oil recovery

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