Method for increasing crude oil recovery ratio through modifying, flooding and washing alternate injection

Abstract

The invention provides a method for increasing crude oil recovery ratio through modifying, flooding and washing alternate injection. The method includes the steps that oil field injection water and permeability adjustment materials are mixed, and a permeability modifying agent is prepared after mixing; the permeability modifying agent is injected into a target reservoir, and the first-level permeability adjustment slug A<1> is formed; the oil field injection water and micellar flooding washing materials are mixed, and a micellar flooding washing agent is prepared after mixing; the micellar flooding washing agent is injected into the target reservoir, and the first-level micellar flooding washing agent slug B<1> is formed; the steps are executed for i times repeatedly, and the i-level permeability adjustment slug A and the i-level micellar flooding washing agent slug B of the target reservoir are formed. The problems that in a chemical flooding system containing polymers,the polymers potentially harm low-permeability areas rich in residual oil and consequently the recovery ratio is low, injection and production are difficult due to long-term injection, the construction time is long, the treatment difficulty of production fluid is large, and application to oil reservoirs with high temperature, high salt or high viscosity heavy oil is difficult are solved, and the crude oil recovery ratio is greatly increased.

Description

technical field [0001] The embodiments of the present invention relate to the technical field of oil exploitation, and in particular to a method for improving crude oil recovery by adjusting, flooding and washing alternately injecting. Background technique [0002] Crude oil plays a pivotal role in the development of the world economy, and the overall demand is growing. However, the discovery of new crude oil reserves in the world is progressing slowly. The average final crude oil recovery degree of general oil reservoirs is less than 50%. On this basis, if every Increasing the oil recovery rate by 1% is equivalent to discovering a 100 million-ton oil field, so the technology of how to greatly increase the oil recovery rate is of great significance. Most oilfields in my country have poor reservoir physical properties, low oil saturation, and rapid production decline, and some oilfields have entered the stage of tertiary oil recovery, with high investment risks, low injection...

AI Technical Summary

Problems solved by technology

Its disadvantages are: ①Limited range of enhanced oil recovery: First, the polymer molecule has a large hydraulic radius of gyration, and the composite flooding fluid preferentially enters the dominant channel. The emulsion formed after the action of crude oil plays a certain role in blocking the low oil content and high permeability area, but at the same time, the macromolecules of the polymer also pollute the high oil content and low permeability area and capillary channels connecting these dominant channels, which has ultra-low Small molecules of surfactants with interfacial tension are difficult to enter these low-permeability areas through natural separation. Surfactants that have the functions of changing capillary wettability, emulsifying and washing oil, and stretching oil droplets are mainly used in high-permeability areas affected by the displacement fluid. However, after long-term displacement in these high-permeability areas, the remaining crude oil is very little and basically tends to the state of residual oil, so the oil washing efficiency of surfactants is not high

Second, as the displacement fluid enters the deep part of the reservoir, the concentration of polymers and surfactants in the deep part of the reservoir has been greatly reduced due to the adsorption of the formation, and after the polymer has undergone formation shearing, heat and biodegradation Its molecular weight has become very small, and the displacement fluid with very low viscoelasticity has a very limited micro-sealing effect on the dominant channels in the deep reservoir. limited

② Difficulty in injection and production fluid treatment: due to long-term continuous injection of polymer flooding and polymer-containing chemical flooding, the polymer injection pipeline corrodes and scales to form a scale-accumulated gel layer, and the diameter of the injection pipeline shrinks seriously, making cleaning difficult

[0005] At present, the first type of reservoirs that can be chemically flooded in domestic onshore oilfields are basically in the late stage of production, and there are still technical difficulties and economic risks in the second and third types of oil reservoirs if chemical flooding is carried out

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