温敏清洗剂原位乳化清洗油基钻井液室内研究

对井筒中残留油基钻井液的高效清除，是实现优质固井、保证井筒完整性的关键。为适应耐温耐盐清洗要求，采用温控乳液转相效应与浊点效应相协同原理，将清洗液直接接触井内油污，原位生成微/纳米乳液以高效清除油污。通过模拟井下温变规律以及浊点、电导率测试，确定了清洗剂配方及其温敏特性，即脂肪醇聚氧乙烯醚与异构羰基聚氧乙烯醚以3： 2复配，在75℃附近从水溶液中开始析出并富集在油污表面，促进油污脱落；油污与清洗液充分混溶，混合液在降温过程中通过形成微/纳米乳液从而促进油污增溶。通过清洗率、润湿角、胶结强度测试，评价了清洗液浓度、温度、盐度及时间对清洗效果的影响，结果表明，50～90℃及含20%钙盐条件下，10 min内5%清洗剂能够高效地清除壁面附着的油基钻井液，清洗效率高达99%以上；除污后壁面可由油润湿状态恢复为水润湿状态，固井胶结强度显著提高。

Cleanup of Oil-based Drilling Fluids Using In-situ Emulsification of Thermoresponsive Surfactants

Efficient removal of residual oil-based mud in wellbore is the key for excellent cementing and wellbore intergrity. To clean the oil-based mud at high temperature and high salt efficiently, the cleaning agent was used to form micro- and nanoemulsion in-situ with the oil-based drilling fluid based on the thermoresponsive phase inversion effect and cloud point effect. By simulating the law of temperature change in the well and testing the cloud point and conductivity, the cleaning agent formula was identified as the mixture of 3% fatty alcohol-polyoxyethylene ether and 2% isomeric carbonyl polyoxyethylene ether. The cleaning agent was thermoresponsive. It could seperate out from its aqueous solution at 75℃ and therefore facilitate the oil phase shedding; then the oil phase mixed with the cleaning fluid and was then solubilized in the cleaning fluid by forming the micro-and nano-emulsion. The effects of cleaning agent concentration, temperature, salinity and time on the cleaning results were investigated by testing the cleaning rate, contact angle and cementing strength. The results showed that the cleaning rate of over 99% of oil-based mud could be reached using 5% thermoresponsive cleaning agent at 50～90℃ and 20% CaCl₂ with 10 minutes, the wall surface could return to water wetting state from the oil wetting state, and the cementing strength was enhanced observably.