一种适用于油基钻井液的表面活性剂隔离液

页岩气钻井过程中采用的油基钻井液极易残留在井壁和套管壁表面，与固井水泥浆产生接触污染。套管壁及井壁长期处在油基钻井液环境中，两界面亲油憎水，给固井作业带来油基钻井液顶替和清洗困难、混浆流变性能变差、混浆强度严重下降、界面胶结质量不良等问题。针对以上问题，对表面活性剂及隔离液进行了如下研究:①调研油基钻井液对水泥浆的接触污染机理；②测定溶液表面张力，验证表面活性剂对清洗效果的影响；③配制表面活性剂水溶液和隔离液，利用模拟套管冲洗法测定清洗效率。实验结果表明，表面活性剂的加入能显著降低水油界面张力，提高清洗效率；配制出了一种清洗效率高达92.86%的三元复配表面活性剂隔离液体系，表面活性剂组成为LAS+JFC-6+AOS （1:1:1）；该隔离液对油基钻井液有良好的清洗效果，可提高界面胶结质量，有助于提升页岩气井的固井质量。 

A Surfactant Spacer for Use in Oil Base Drilling Fluid

In shale gas drilling, the residues of oil base drilling fluid on the borehole wall and the surface of the casing strings have long been a problem. The residual oil base drilling fluid will inevitably be mixed with and therefore render contamination to cement slurry. The surface of casing and the borehole wall, which are long in contact with oil base drilling fluid, can become lipophilic or hydrophobic, thus bringing about many problems, such as difficulties in displacing the oil base drilling fluid and cleansing the casing string, poor rheology of the mixed slurry, reduced strength of the contaminated cement slurry, and poor bonding of the interfaces between cement sheath and casing string and the interfaces between cement sheath and the borehole wall. Laboratory studies have been conducted on surfactants and spacers to resolve the problems mentioned above. The studies included the following:1) investigating the mechanisms of the contact contamination between oil base drilling fluid and cement slurry; 2) verifying the flushing efficiency of surfactants by measuring surface tension; and 3) measuring the flushing efficiency of surfactant solution and spacer using simulated casing flushing experiment. The results of the studies showed that use of surfactant remarkably decreased the oil-water interface tension, hence enhanced the flushing efficiency. A compounding surfactant spacer, having a flushing efficiency of 92.86%, was formulated with three surfactants in a ratio of LAS:JFC-6:AOS=1:1:1. The spacer was able to enhance the bonding quality of the interfaces between casing and cement sheath and the interfaces between cement sheath and borehole wall, and was helpful in improving the quality of shale gas well cementing.