Viscosity-reducing oil displacement agent for common heavy oil reservoirs, and preparation method thereof

Abstract

The invention discloses a low-tension viscosity-reducing oil displacement agent, which is used for common heavy oil reservoirs, has a good viscosity-reducing effect, has good compatibility with formation water, can form ultra-low interfacial tension with crude oil, and is prepared from the following components by weight: 30-50% of an alkyl alcohol polyoxyethylene ether sulfate salt, 15-25% of a nonionic surfactant, 15-25% of an anionic surfactant, 2-5% of an organic solvent, 0.1-3% of sodium chloride, and 5-25% of water. According to the present invention, during the use, the low-tension viscosity-reducing oil displacement agent and the polyacrylamide polymer form the composite oil displacement system, wherein the polyacrylamide polymer can provide effects of water phase viscosity increasing, water-oil mobility ratio reducing, conformance expanding and profile control expanding, and the low-tension viscosity-reducing oil displacement agent can provide effects of oil-water interface tension reducing, oil displacement efficiency improving and crude oil viscosity reducing so as to further improve the water-oil mobility ratio, such that the extraction rate of the common heavy oil reservoir can be substantially improved through the synergetic effect of the polyacrylamide polymer and the low-tension viscosity-reducing oil displacement agent.

Description

technical field [0001] The invention relates to a low-tension viscosity-reducing oil displacement agent suitable for ordinary heavy oil reservoirs and capable of improving the recovery rate of ordinary heavy oil reservoirs and a preparation method thereof, belonging to the technical field of oil recovery. Background technique [0002] With the increasing consumption of oil, the amount of conventional oil resources that can be exploited is decreasing, and the development of heavy oil reservoirs is of great significance to solve the contradiction of oil resource shortage. According to my country's heavy oil classification standards, ordinary heavy oil refers to crude oil with a crude oil viscosity of 50-1000mPa·s under oil layer conditions, of which the crude oil viscosity of sub-1 ordinary heavy oil is 50-100mPa·s, and sub-2 ordinary heavy oil The crude oil viscosity is 100-1000mPa·s. Due to the high viscosity of ordinary heavy oil, high water-oil mobility ratio, and low wate...

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Problems solved by technology

Although polymer flooding has an obvious effect of reducing water and increasing oil production in conventional crude oil reservoirs, the flooding effect on ordinary heavy oil reservoirs with high viscosity is poor. There are two main reasons for this: first, the development of ordinary heavy oil reservoirs requires However, under high-temperature and high-salt reservoir conditions, conventional polyacrylamide polymers are subjected to high-temperature degradation and high-salt degradation, and the viscosity of the polymer solution is greatly reduced, resulting in the increase of the polymer to the water phase. Sticky effect is very limited

Secondly, for heavy oil with strong viscosity, it is difficult for the polymer to drive out the remaining oil in the rock pores

It is difficult to use polymer flooding alone to meet the high-efficiency development needs of high-temperature and high-salt ordinary heavy oil reservoirs in my country's Shengli and Henan oilfields

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