油井水泥浆与多功能钻井液泥饼界面离子扩散阻碍机理

对泥浆转化为水泥浆（MTC）固井液水化离子可扩散进入多功能钻井液泥饼的机理已有研究，但对油井水泥浆水化离子不能扩散运移进入多功能钻井液泥饼的机理尚未清楚。采用离子色谱仪、原子吸收分光光度计和X射线衍射仪，从油井水泥浆与MTC固井液离子组成的差异性入手，对油井水泥水化离子向多功能钻井液泥饼扩散运移的阻碍机理进行了研究。结果表明，油井水泥浆中Ca²⁺的质量分数远远大于MTC固井液中Ca²⁺的质量分数，在油井水泥与多功能钻井液泥饼界面生成了CaCO₃、CaSO₄和Ca(OH)₂，而MTC固井液中Na⁺的质量分数则大于油井水泥浆中Na⁺的质量分数;Na⁺可改变泥饼中活性颗粒表面的ζ电位和破坏钻井液有机处理剂表面形成的水膜是MTC固井液中水化离子能扩散运移进入多功能钻井液泥饼的主要原因，而在油井水泥与多功能钻井液泥饼界面生成的CaCO₃、CaSO₄和Ca(OH)₂沉淀堵塞孔道则是油井水泥浆水化离子不能扩散运移进入多功能钻井液泥饼的主要机理。

Hindering mechanism of ion diffusion at the interface between oil-well cement slurry and mud cake from multifunctional drilling fluid

The mechanism that hydration ions in the mud to cement slurry (MTC) cementing fluid can diffuse and migrate into the mud cake from multifunctional drilling fluid has been well researched, while it still remains unclear at present why hydration ions in the oil-well cement can not diffuse into the mud cake from multifunctional drilling fluid. Herein, we examined differences in ion compositions of the oil-well cement and the MTC cementing fluid by means of ion chromatography, atomic absorption spectrophotometer and X-ray diffraction, and investigated thoroughly the hindering mechanism that prevent hydration ions in the oil-well cement from diffusing and migrating into the mud cake from multifunctional drilling fluid. The result indicated that Ca²⁺ in the oil-well cement has a mass fraction much higher than that in the MTC cementing fluid and can form CaCO₃, CaSO₄ and Ca(OH)₂ at the interface between the oil-well cement and the mud cake from multifunctional drilling fluid. The mass fraction of Na⁺ in the MTC cementing fluid, however, is much higher than that in the oil-well cement, moreover, Na⁺ can change the ζ potential on the surface of active particles in the mud cake and destroy the water film formed on the surface of organic additives from drilling fluid, which are the major reasons that make hydration ions in the MTC cementing fluid capable of diffusing and migrating into the mud cake from multifunctional drilling fluid. Whereas, the CaCO₃, CaSO₄ and Ca(OH)₂ formed at the interface of the oil-well cement and the mud cake from multifunctional drilling fluid may precipitate and block apertures, which is attributed to the main hindering mechanism that prevents hydration ions in the oil-well cement from diffusing and migrating into the mud cake from multifunctional drilling fluid.