基于压力控制靶向释放的微胶囊化钻井液润滑剂制备及作用机理

Friction and drag in oil and gas drilling engineering restrict the object of safety, high quality and high efficiency drilling. Addition of lubricants into drilling fluid is an important method to reduce friction and drag. Conventional drilling fluid lubricants influence drilling fluid rheological properties easily. Meanwhile, lubricants are prone to be diluted, which results in the fast decrease of lubricity. Microcapsules containing high efficient and environmental friendly lubricants are proposed in this project, which will release at high friction and torque points in down hole conditions. The targeted released lubricants will effectively lubricate and reduce friction and drag because of local high concentration. Based on friction characteristics of down hole condition, considering the requirement of drilling fluid lubricity and environment protection, high efficient lubricant core material will be selected. Environmental friendly microcapsule lubricant will be prepared through the microcapsule structure design. The stability, lubricity, compatibility and environmental performance will be evaluated systematically, and the influence of pressure on lubricity will be focused. The response relation between microcapsule structure and pressure controlled release will be investigated, and the method of controlling microcapsule release will be established. The tribological mechanism of microcapsules will be investigated. The study will provide scientific basis for developing novel and high efficient drilling fluid lubricants, and provide a novel method for reducing down hole friction and torque with high performance.

油气钻井工程中的摩阻和扭矩问题严重制约着安全、优质、高效钻井目标的实现。加入润滑剂改善钻井液润滑性能是降低摩阻和扭矩的重要手段。传统钻井液润滑剂存在对钻井液流变性影响显著、易被稀释导致润滑性迅速下降等不足。本项目提出制备包覆环保型润滑剂的微胶囊，在井下高摩阻和扭矩处受摩擦挤压作用破裂，润滑剂靶向释放，形成局部高浓度并高效发挥润滑作用以降摩减阻的思路。基于井下摩擦特征分析，结合钻井液润滑性及环保要求，研选高效润滑性芯材，设计微胶囊结构，优化制备出具有压力控制释放特征的环保型微胶囊化润滑剂。综合评价微胶囊的稳定性、润滑性、配伍性和环保性能，重点考察其润滑性随压力的变化规律。探究微胶囊化润滑剂结构与压力控释之间的响应关系，建立微胶囊释放的调控方法，揭示微胶囊化润滑剂的摩擦学机理。本项目研究将为开发新型高效钻井液润滑剂提供科学依据，并为有效降低井下摩阻和扭矩开辟新的途径。

本项目以基于压力控释的钻井液用微胶囊润滑剂为研究对象，针对钻井液用微胶囊润滑剂的合成、综合性能与润滑机理等方面进行研究。具体为：（1）采用单凝聚法，以壳聚糖微胶囊为壁材，环保型植物油为芯材，优化得到微胶囊的最优制备条件：芯壁比为3:1，复配乳化剂HLB值为11，乳化条件为3000r/min搅拌10min，反应转速为600r/min，反应pH值为7，反应温度为50℃，固化剂与壁材质量比为1:1，固化时间为1h。制得的微胶囊润滑剂芯材含量为59.83%，在水相环境中可耐90℃高温；（2）采用复合凝聚法，以壳聚糖和海藻酸钠为壁材，环保型植物油为芯材，优化得到微胶囊的最优制备条件：壳聚糖浓度为0.75%，海藻酸铵浓度0.3%，乳化剂为Tween-80和Span-80按1:1复配，乳化剂加量为0.5g，芯壁比为3:1，乳化条件为3000r/min剪切5min，反应转速为600r/min，反应pH值为6，固化剂D溶液浓度为0.6%，反应温度为45℃，反应时间为2h。该条件下制备的微胶囊润滑剂芯材含量为67.05%，在水相环境中可耐120℃高温；（3）采用喷雾干燥法，以脲醛树脂为壁材，环保型植物油为芯材，优化得到微胶囊的最优制备条件：尿素与甲醛质量比为1:1，芯壁比为2:3，乳化剂与芯材质量比为1:10，乳化条件为11000r/min剪切20min，喷雾干燥工艺为：喷口直径0.7mm，风机频率40Hz，进料速度420mL/h，喷雾气流压力0.069MPa，进风温度180℃。该条件下制备的抗温树脂微胶囊润滑剂芯材含量为40%，在水相环境中可耐150℃高温。