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摘要
In oil and gas well drilling, the low bond strength between the cement sheath and the borehole wall (mud cakes) is an important factor causing gas channeling along the interfaces between the cement sheath and the borehole wall. In laboratory experiment, a low viscosity high penetrating capacity epoxy resin (HP epoxy resin) containing reactive thinner was mixed with a cement slurry. The epoxy resin in the mixed cement slurry can penetrate and diffuse into the mud cakes under high pressures. The epoxy resin, after becoming consolidated, greatly improved the bond strength between the cement sheath and the mud cakes. The experimental results have shown that the consolidated epoxy resin have high compressive strength and can be uniformly mixed with cement slurry with the aid of Tween-80, a surfactant. The properties of the cement slurry modified with the HP epoxy resin meet the requirements of field operations. By contact angle measurement and SEM analysis, it was found that the epoxy resin improved the bond strength between the cement sheath and the borehole wall through a “penetration-diffusion-bonding” process. A cement slurry containing 5% HP epoxy resin had 1 d compressive strength of 24.3 MPa. When this cement slurry was bonded with mud cakes, the bond strength of the solidified mud cake of 1 mm in thickness can be as high as 0.45 MPa. When the content of the HP epoxy resin in the cement slurry was increased to 10%, the bond strength was raised to 0.55 MPa accordingly. From the micromorphology of the consolidated mud cakes it was found that the HP epoxy resin penetrated and diffused into the mud cakes from the cement slurry, making the surface of the mud cakes denser, hence improving the bond strength of the interfaces between the modified cement slurry and the mud cakes. ? 2022 North China Petroleum Administration Drilling Technology Research Institute.
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