Viscosity-reducing oil displacement agent and oil displacement system for heavy oil reservoirs

Abstract

The invention discloses a viscosity-reducing oil displacement agent for heavy oil reservoirs, wherein the components comprise, by weight, 20-60% of an emulsifier, 1-5% of an ester-based compound, 0.2-2% of a wetting agent, and the balance of water. The invention further discloses a viscosity-reducing oil displacement agent-polymer system for heavy oil reservoirs, wherein the viscosity-reducing oil displacement agent-polymer system comprises 0.1-1% of the oil displacement agent, 0.05-0.3% of a polymer and the balance of water, and the polymer is polyacrylamide with a molecular weight of 8000000-20000000. According to the present invention, the viscosity-reducing oil displacement agent and the viscosity-reducing oil displacement agent-polymer system can provide good effects of viscosity reducing and emulsifying for heavy oil, can substantially reduce the viscous force of heavy oil in rock pores, can provide good profile control and water blocking effect, can effectively improve oil displacement efficiency, can improve heavy oil recovery, and are suitable for heavy oil reservoirs with a stratum viscosity of more than 200 mPa.s.

Description

technical field [0001] The invention relates to a viscosity-reducing oil-displacement agent and an oil-displacement system suitable for heavy oil reservoirs, belonging to the technical field of oil recovery. Background technique [0002] In recent years, the demand for oil has continued to rise, and the marginal heavy oil and bitumen reservoirs that were considered worthless in the past have become effective resources with economic value. Heavy oil contains more colloids and asphaltenes, has high viscosity, poor fluidity, is difficult to mine, and has a low recovery factor. [0003] Polymer flooding is a commonly used heavy oil recovery technology. This technology increases the viscosity of the water phase and reduces the permeability by dissolving the polymer in water, thereby reducing the mobility ratio and increasing the sweep coefficient of water flooding. Surfactants are often used in combination with polymers to further improve water flooding efficiency by using surfa...

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Problems solved by technology

[0011] These oil displacement systems have some common disadvantages, they are suitable for conventional crude oil reservoirs, but the oil displacement effect is poor for heavy oil reservoirs with higher viscosity

There are a large amount of heavy oil in my country's Shengli, Henan, Zhongyuan, Tahe and other oil fields, and the viscosity of the formation reaches more than 200mPa·s. It is difficult to achieve high oil displacement efficiency with the existing oil displacement system

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