水合物层固井水泥热能存储剂载体研制及承载机理研究

The heat storage agent can absorb the hydration heat of well cement, and also can reduce the heat transmitted from the wellbore to the formation via the cement sheath, which is conducive to the stabilization of the hydrate in deep water. However, the heat storage agent is prone to overflow, coalesce and stratify in cement slurry. To carry the heat storage agent by use of carrier is an effective method to avoid the negative effect on cement slurry. Therefore, this project is to investigate the carrier for heat storage agent with high strength and high carrying capacity, as well as the carrying mechanism. In addition, the interaction between carrier and well cement will be analyzed. The preparation method and formation mechanism of hollow microspheres is researched to realize the construction of hollow microspheres with spherical wall opening. Based on the influence factors and rules, the regulation and control method of physical properties of hollow microsphere is established. Combining the carrying mode and the carrying capacity model, the carrying mechanism of hollow microsphere for heat storage agent is analyzed, and the regulation method of the carrying capacity is also established. By establishing the sedimentation rule model of microsphere carrier in cement slurry, and analyzing the influence of microsphere carrier on the performance of cement slurry, the interaction mechanism between microsphere carrier and oil well cement is confirmed. And finally the hydration heat of cement with different dosage of carriers is evaluated. This project is of great significance to effectively seal gas hydrate layer, and could provide reference for the research and development of other type oil well cement admixture carriers.

热能存储剂可以吸收固井水泥水化热量，也可降低由井筒通过水泥环传至地层的热量，有利于海洋深水水合物层的稳定。但是热能存储剂在水泥浆中很容易出现溢出、聚并和分层。将热能存储剂吸入载体内进行承载，是避免热能存储剂对水泥浆不利影响的有效措施。因此本项目拟对具有高强度、高装载能力的热能存储剂载体及其承载机理进行研究，并分析载体与水泥浆的相互作用。通过建立中空微球制备方法及形成机理，完成球壁开孔中空微球的构建，并基于其物性参数的影响因素和规律，建立中空微球物性参数调控方法；结合中空微球对热能存储剂的承载方式和承载量模型，分析承载机理，建立承载量调控方法；通过建立微球载体在水泥浆中沉降规律模型，并分析微球载体对水泥浆性能的影响，明确微球载体和水泥浆之间的相互作用机制，最终对不同载体加量的水泥水化放热量进行评价。本项目对有效封固水合物层具有重要意义，也可为其它类型油井水泥外加剂载体研制提供借鉴。

海洋深水水合物层封固时，油井水泥在凝固过程中产生大量的水化热，导致固井层段水合物分解，对尚未发展足够强度的水泥环产生巨大的安全隐患，从而引发固井质量问题，甚至安全事故。目前现有的固井水泥体系水化峰值较高，不能有效满足水合物层固井的需要。本文在自制的中空微球的基础上，构建一套中空微球封装水泥热能存储剂方法，发明了热能存储剂微球，为降低固井水泥的水化放热提供技术保障。.采用反相悬浮聚合工艺，以偏高岭土等为基础材料，通过对微球制备影响因素的优化实验，得出了混合水、激活剂、致孔剂等的加量对微球的表观形态、粒径以及中空体积的影响规律，并通过正交试验优化出了制备微球的最优配方，制备出了一种空心微球。该制备工艺条件下，微球的成球率高、微球外观光滑、微球粒径在310~470μm之间，成孔率高达90%以上、孔径比达60%以上，正交优化试验确定微球制备的最佳配方为：水加量为110%，氢氧化钠加量为13%，硅酸钠加量为30%，致孔剂加量为80%。.研究研选发现石蜡S6具有较好的储热能力和稳定性能，可以作为热能存储剂。优选出一种真空抽吸法，实施高强度中空微球（弹性模量达到56.41 GPa）对热能存储剂的承载，其承载率高达38%。对水性环氧树脂和丙烯酸材料两种封装材料，分别构建出了搅拌涂覆法和流化干燥法两种封装工艺；封装效果评价表明，水性环氧树脂封装除了具有耐海水、水泥腐蚀性外，还有更好的耐碱性。封装储能微球加入水泥后能够明显降低水化放热峰值（加量20%时，降低水化热28.85%），延长水泥的稠化时间，对水泥浆的密度基本没有影响，具有良好的分散性和稳定性，且固化后与水泥石胶结稳定；随封装储能微球加量的增多，水泥浆的剪切应力减小，屈服应力增大，有效改善了水泥浆的流变性能。微球加量小于10%时，对水泥3 d以上的强度没有影响；加量10%-20%时，水泥抗压强度也满足海洋深水固井中对强度的要求。