A kind of non-acid mud cake flushing agent, flushing liquid and flushing method

Abstract

The invention discloses a nonacid mud cake flushing agent, a flushing liquid and a flushing method. The nonacid mud cake flushing agent consists of the following components in parts by mass: 40-50 parts of sodium tripolyphosphate, 10 parts of ammonium persulfate and 3-5 parts of an anionic surfactant. The flushing agent and water can be conveniently prepared into the flushing liquid; in the flushing liquid, sodium tripolyphosphate takes the effect of a dispersant, ammonium persulfate takes the effect of an oxidant, and the anionic surfactant can take the effects of wetting, permeation, emulsification, dispersion, solubilization and bubbling; the components achieve a synergistic effect; the pertinence is high; mud cakes on the wall of a well can be efficiently wetted, decomposed and removed, so that reservoir protection is facilitated and serious corrosion caused to a pipe column by adopting an acid-washing flushing liquid is avoided; and a mixed liquid after the flushing by the flushing liquid is high in stability, has high suspension stability, and is free of sedimentation and liable to flow back during field construction, thereby reducing underground safety accidents.

Description

technical field [0001] The invention belongs to the technical field of chemical agents for petroleum drilling engineering, and in particular relates to a non-acid mud cake flushing agent, a flushing liquid and a flushing method. Background technique [0002] In the oil drilling process, the mud cake is formed when the free water of the drilling fluid enters the rock formation during the filtration process, and the solid phase particles in the drilling fluid adhere to the well wall. Good quality mud cake can protect the well wall and effectively reduce fluid loss. However, after the drilling is completed, when oil production is required, the formed mud cakes need to be removed, because these mud cakes block the pores around the well wall, so that the oil in the oil layer around the well wall cannot flow into the well, reducing the reservoir pressure. Permeability increases oil and gas flowback pressure, resulting in reduced oil and gas production, and is not conducive to res...

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Problems solved by technology

[0004] Flushing fluid is usually prepared by adding surfactants to water or diluting and mixing with drilling fluid. However, the traditional flushing fluid has a weak ability to wash away drilling fluid and mud cake, and cannot efficiently clean the drilling fluid on the well wall. It is impossible to effectively remove the thin, tough and dense mud cake formed on the well wall; in response to the above problems, many new flushing fluid systems have been launched

CN103965845A discloses a shale gas horizontal well cementing flushing fluid, which mainly consists of 2 to 10 parts of nonionic surfactants, 2 to 7 parts of anionic surfactants, 2 to 4 parts of organic acids, and 0.5 parts of viscosity and shearing agents. ~5.0 parts, clean water 72~100 parts; the flushing liquid has a certain shear force and viscosity, and has a strong scouring ability; but because the polymer in the mud cake has strong cohesiveness, the flushing liquid still The mud cake cannot be effectively wetted and decomposed, and the effectiveness of its flushing still needs to be further improved

The oxidizing substances in the flushing fluid can promote the degradation of organic polymers in the mud cake, thereby effectively reducing the viscosity of the drilling fluid and the structural strength of the filter cake, which is conducive to improving the flushing efficiency; however, the composition of the flushing fluid is complex and the composition The organic acid in the oil is easy to cause corrosion to the pipe string, which increases the difficulty of downhole operation in the later stage

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