Compound plug removal agent for tight sandstone oil reservoir

Abstract

The invention discloses a compound plug removal agent for a tight sandstone oil reservoir, and belongs to the technical field of oilfield exploitation. The compound plug removal agent is composed of prepad fluid, main body fluid and post-pad fluid, wherein the prepad fluid and the post-pad fluid each contains hydrochloric acid, potassium chloride, ethylenediaminetetraacetic acid, water plug removal agents, corrosion inhibitor and ethylene glycol butyl ether, and the main body fluid contains fluosilicic acid, hydrochloric acid, potassium chloride, ethylenediaminetetraacetic acid, water plug removal agents, corrosion inhibitor and ethylene glycol butyl ether. According to pollution plugging which possibly occurs in the development process of the tight sandstone oil reservoir, corresponding treatment fluid in the compound plug removal agent is sequentially infused into the reservoir according to the three stages of front, middle and rear, and the purposes of removing reservoir plugging, increasing effective permeability of the reservoir, improving the plug removal effect and recovering per-well production can be achieved. The hydrochloric acid is matched with the fluosilicic acid to serve as the components of the main body fluid, plug removal is achieved, and meanwhile the reservoir is protected against secondary pollution.

Description

technical field [0001] The invention relates to an oil well plug-removing agent, in particular to a composite plug-removing agent for tight sandstone reservoirs, and belongs to the technical field of oil field exploitation. Background technique [0002] During the process of oil well drilling and completion to production, the contact of foreign fluid with reservoir rock and reservoir fluid may cause the clogging of the seepage channel of the reservoir. During the production process of old wells, changes in formation temperature, pressure and fluid properties may also cause blockage of reservoir seepage channels, reducing permeability. For the above situation, plugging removal by injecting plugging removal agent into the formation is an effective measure to restore and increase reservoir permeability. However, for tight sandstone reservoirs, due to their low porosity and permeability, and the long contact time between the reservoir and the drilling fluid during horizontal we...

AI Technical Summary

Problems solved by technology

However, the mass fraction of organic acids and inorganic acids is relatively small. Although it can achieve the effect of unblocking the near-wellbore area, it is not clear whether the effective permeability of the reservoir can be further increased after unblocking.

However, for the plugging removal method that simply uses hydrochloric acid or hydrofluoric acid as the plugging agent, the reaction rate of acid rock is difficult to control, and the clay mineral composition in the reservoir is complex, and the composition of the plugging agent is too simple to cause secondary pollution of the reservoir.

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