钻井液用包被剂对固井水泥浆体系的影响

针对钻井液与固井水泥浆相互接触时会使混浆流动性能变差的问题，实验研究了包被剂对固井水泥浆稠化时间、流变性能和抗压强度的影响。采用红外光谱、X射线衍射仪以及扫描电镜探究了包被剂对固井水泥浆的污染机理。同时利用电导率评价方法，比较了掺入包被剂前后固井水泥浆电导率的变化。研究结果表明，包被剂的掺入会降低水泥浆的流动度，当加量为0.6%时，水泥浆的流动度与纯水泥相比降低了52%；电导率实验分析表明，掺入包被剂后的水泥浆水化进行到12 h时，才进入加速期；包被剂的掺入降低了固井水泥浆水化的反应速率，延缓了其水化进程，从而导致固井水泥浆的抗压强度发展缓慢，在90℃养护条件下，掺量为0.2%时，其3 d强度与纯水泥相比降低了12.8%。包被剂中—OH、—CONH2、—COO-等具有吸附性能的官能团会吸附于水泥颗粒上，且包被剂中的亲水基团与固井水泥浆中的Si—O形成氢键，在水泥颗粒表面形成一层溶剂膜，阻碍了水与水泥颗粒的接触。

Effects of Drilling Fluid Encapsulators on Well Cement Slurries

When a drilling fluid is mixed with a cement slurry, the flow of the mixture will become very poor. In a laboratory study, the effects of drilling fluid encapsulators on the thickening time, rheology and the compressive strength of cement slurries were investigated. Using IR, XRD and SEM, the mechanisms with which the cement slurries are contaminated by the drilling fluid encapsulators are studied. Electric conductivity method was also used to evaluate the changes of the electric conductivity of cement slurries before and after the cement slurries are mixed with drilling fluid encapsulators. The study results showed that the mobility of a cement slurry is reduced when an encapsulator is mixed with the cement slurry; a pure cement slurry contaminated with 0.6% encapsulator has its mobility reduced by 52%. Electric conductivity experiment showed that the hydration process of a cement slurry, which is contaminated with a drilling fluid encapsulator, begins accelerated only after 12 hours of hydration. The mixing of a drilling fluid encapsulator into a cement slurry will slow down the hydration process of the cement slurry, leading to a slow development of the compressive strength of the cement slurry. A cement slurry containing 0.2% drilling fluid encapsulator and cured at 90 ℃, has a 3 d strength that 12.8% lower than that of the pure cement slurry. The adsorption groups in the molecules of the encapsulator, such as —OH, —CONH₂, —COO- etc., can be adsorbed onto the particles of the cement, and the hydrophilic groups of the encapsulator can form hydrogen bond with the Si—O bond in the cement molecules, thereby forming a solvent film on the surfaces of the cement particles, which in turn hinders the contact of water with the cement particles.