A gas generation system for improving seepage capacity of tight oil reservoirs and its application

Abstract

The invention provides a gas-producing system capable of improving permeability of a tight oil reservoir and application thereof, belonging to the technical field of oilfield development. The gas-producing system comprises a microcapsule and hydrochloric acid; the microcapsule uses a mixture of urea and sodium nitrite as a core material and a mixture of azodiisobutyronitrile, styrene, methyl methacrylate and methacrylic acid as a capsule dressing. In operation, nitrite and the microcapsule are injected into a stratum to a predetermined depth; and the microcapsule undergoes corrosion under stratum conditions and chemically reacts with hydrochloric acid to produce a great amount of gas and release a great amount of heat, so local high pressure is formed in a predetermined part. According to the invention, effective seepage channels of difficult-to-produce reserves such as an ultralow-permeability oil reservoir and the tight oil reservoir are increased so as to improve permeability, increase local energy of reservoirs and the flowback rate of raffinate, and reduce reservoir contamination, so the purpose of improving the recovery efficiency of the difficult-to-produce reserves is achieved.

Description

technical field [0001] The invention relates to the technical field of oilfield development. Background technique [0002] As the developed oilfields enter the high water cut period and the development of new proven reserves becomes more and more difficult, and the proportion of hard-to-produce reserves such as ultra-low permeability reservoirs and tight oil reservoirs in the newly discovered reserves is increasing, so the difficult-to-produce reserves The extraction of reserves is becoming more and more important. However, the reservoir characteristics of tight oil reservoirs bring great challenges to the development. The main problems faced by the development of such reservoirs are low formation porosity and permeability, low natural energy of the oil field, and low formation water absorption capacity. How to effectively improve the seepage capacity of this kind of reservoir is particularly important for its exploitation. [0003] At present, the main ways to improve the...

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Problems solved by technology

[0004] 1. The corrosion problem caused by the presence of acid in the operation process brings troubles to subsequent production

In addition, for oil reservoirs with low formation pressure, it is difficult to flow back the residual acid of the acidizing fluid, and if it stays in the formation, it will easily cause secondary pollution to the reservoir, reduce the acidizing effect of the acidizing fluid, and even make the acidizing ineffective

[0005] 2. The fracturing fluid causes damage to the reservoir: (1) The fracturing fluid causes problems such as expansion, dispersion, migration, and blockage of the formation clay; Phase permeability becomes smaller; (2) After the fracturing fluid is broken and hydrated, residual solid particles or incomplete gel breaking will block formation throats and fractures; (3) Filtration results in the formation of dense filter cakes on the surface of fractures

At the same time, the filtrate enters the formation fractures to form concentrated fracturing fluid, which makes it difficult to break the gel, resulting in greatly reduced seepage channels

CO 2 Although foam fracturing can avoid the damage of fracturing fluid to the reservoir, the unevenness of the foam in the reservoir affects the fracturing effect. In addition, the technical requirements for equipment are high, the cost of measures is high, and there are safety risks

[0006] 3. After carrying out acidizing, fracturing and acid fracturing measures, the extent to which seepage capacity can be improved is limited

[0007] 4. The cost is high, the effect of single fracturing is limited, and the cost of multi-stage fracturing is too high

This increases the difficulty and workload of construction

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