A polymer flooding method for heavy oil reservoirs

Abstract

The invention relates to a polymer flooding method for a heavy oil reservoir. The method comprises steps that an injection-production well network well, whose center well is a horizontal well and an edge-corner well is a straight well is selected in a target heavy oil reservoir and a horizontal well, the horizontal well works as an injection well and the straight well works as a production well; emulsification viscosity reducer solution is injected into the horizontal well; polymer solution with gradually increasing concentration is continuously injected into the horizontal well after the emulsification viscosity reducer solution injection is finished, so a front-mounted protective section plug, a main body section plug and a back-mounted protection section plug can be orderly formed; displacing liquid is continued to injected after injection to the back-mounted protection section plug is completed; and heavy oil exploited from the straight well is collected when the emulsification viscosity reducer solution and the polymer solution are injected to the horizontal well. By the use of the oil flooding method, exploitation methods for the heavy oil reservoir, especially the thin layerheavy oil reservoir can be enriched; polymer flooding technology exploiting effect can be obviously improved; and heavy oil reservoir exploitation level can be greatly improved.

Description

technical field [0001] The invention relates to the technical field of oilfield exploitation, in particular to a polymer flooding method for heavy oil reservoirs. Background technique [0002] At present, steam thermal recovery is the main method for heavy oil reservoirs, but horizontal wells in thin-layer heavy oil reservoirs are developed by means of steam huff and puff and HDCS huff and puff. The rate is only 15%-20%, there is still a large amount of remaining oil that is difficult to recover, and the heat loss is more than 65%, resulting in poor development benefits; at the same time, steam flooding of horizontal wells in heavy oil reservoirs, the oil-gas viscosity ratio is as high as Hundreds of thousands, easy to steam channeling, field practice shows that horizontal wells drilled with a high proportion of high-permeability strips, the probability of steam channeling is greater, making it difficult to achieve balanced displacement by steam flooding in horizontal wells....

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Problems solved by technology

At present, vertical well polymer flooding is mainly used in ordinary heavy oil reservoirs in China, and this method is mainly suitable for ordinary heavy oil with a crude oil viscosity of 50-120mPa·s under formation conditions; horizontal well polymer flooding is used in foreign heavy oil reservoirs However, due to the presence of high-permeability strips with high permeability in the formation, the viscosity difference between the oil and water phases in heavy oil reservoirs is very large, horizontal wells are directly displaced by polymers, and the sweeping range is small, which has a great risk of occurrence Polymerization channeling, resulting in poor polymer flooding effect

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