A kind of pH sensitive water-absorbing resin suitable for oil well cement slurry and its application

Abstract

The invention discloses a pH-sensitive water-absorbing resin suitable for oil well cement slurry and its application. It is composed of distilled water, polymerized monomers, mixing aids, crosslinking agents and initiators, wherein the added amount of polymerized monomers is 1 / 2 of the quality of distilled water. 30% to 100%, the amount of mixing aids is 16% to 67% of the mass of polymerized monomers, the amount of crosslinking agents is 0.2% to 1% of the mass of polymerized monomers, and the amount of initiators is 1% of the mass of polymerized monomers 0.4% to 1%. The pH-sensitive water-absorbing resin prepared by the present invention is added to the oil well cement slurry, and absorbs less water in the alkaline environment of the cement slurry, which greatly reduces the influence of the water-absorbing resin on the rheology of the oil well cement slurry and the compressive strength of the cement stone after curing. Guarantee the smooth implementation of cementing operations; the water-absorbing resin absorbs a lot of water in the neutral environment of formation water, so when it encounters formation water passing through micro-fractures, it will absorb water and swell, plug micro-fractures, and realize self-sealing of oil well cement stone micro-fractures when encountering water Blocking.

Description

technical field [0001] The invention relates to a pH-sensitive water-absorbing resin, in particular to a pH-sensitive water-absorbing resin suitable for oil well cement slurry and its application. The invention belongs to the fields of oil and gas well cementing and oil field chemistry. Background technique [0002] The main purpose of well cementing is to protect the production string and isolate the adjacent oil, gas and water layers. After the cement solidifies, a vertical hydraulic isolation system is formed. Therefore, it must be maintained during the entire life of the oil and gas well and after it is scrapped. Effective interlayer isolation can be achieved. Cement stone is a brittle material. As the exploration and development goals become more complex, the cement stone is affected by stress and temperature changes, and is inevitably damaged to form micro-cracks, resulting in formation fluid channeling, oil and gas leakage, Casing corrosion and other accidents serio...

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Problems solved by technology

[0004] Chinese patent CN201410818719.6 prepared a chitosan cross-linked polymaleic anhydride superabsorbent resin, the resin is pH sensitive, but chitosan has poor thermal stability under high temperature conditions and is easy to degrade, so it is not suitable for high temperature environment of oil well cement Middle; water-absorbing gels prepared by international patents WO2004064816A1, WO1998001421A1, Chinese patents CN2015107292937.1, CN200710042753.9, CN200710042753.9, etc. The pH sensitivity of the water-absorbing gel is that it absorbs more water in an alkaline environment than in a neutral environment; Chinese patent CN201310485548 The pH-sensitive hydrogel prepared in .5, its pH-sensitive performance is reflected in that the pH value affects the adsorption of the hydrogel to heavy metal ions, and its pH-sensitive water absorption and swelling performance is not explained; the pH-sensitive water prepared in Chinese patent CN200910217799.9 Gel, its pH-sensitive performance is reflected in the fact that the hydrogel absorbs more water in a neutral environment than in an acidic environment, and does not explain its water-absorbing swelling performance under alkaline conditions

Chinese patent CN102311517 prepares a superabsorbent resin with pH-sensitive properties, which controls the reversible breakage or combination of sensitive groups by adjusting the pH value to control the degradation / recovery of the water-absorbent resin. The use condition is weakly alkaline and cannot be applied. Plugging micro-cracks in oil well cement

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