盐水侵污对油基钻井液性能的影响及机理

Influence and Mechanism of Brine Fouling on Properties of Oil-based Drilling Fluid

在塔里木油田大北、克深、博孜区块深层油井的勘探开发过程中,经常钻遇高压盐水层,地层高压盐水的侵污使钻井液的性能变差甚至破坏,严重影响钻井作业的顺利进行。室内实验通过测试盐水侵污对油基钻井液性能的影响,分析了盐水侵污机理,并给出了相应的盐水侵污维护方案。研究结果表明:盐水侵污油基钻井液导致体系的黏度先减小后增大,在20%盐水侵污时黏度由118 mPa·s下降至96 mPa·s,在30%盐水侵污时黏度开始上升,在50%盐水侵污时黏度超过了黏度计的量程。破乳电压逐步下降,在60%盐水侵污时破乳电压由468 V下降至90 V。体系的盐水侵污量为10%时,建议正常维护并补充适当的主辅乳化剂,侵污量为10%数30%时,建议分开处理并补充适当的柴油及处理剂,侵污量在30%以上时建议地面收集处理。合理地选择钻井液性能维护方案有利于减少井下复杂情况发生的概率。

In the exploration and development process of deep oil wells in Dabei,Keshen and Bozi blocks of Tarim oilfield,high-pressure salt water layer is often drilled,which makes the performance of drilling fluid worse or even damaged,seriously affecting the smooth drilling operation.Through testing the influence of salt water intrusion on the performance of oil-based drilling fluid,the mechanism of salt water intrusion was analyzed,and the corresponding salt water intrusion maintenance scheme was given.The results showed that the viscosity of the system first decreased and then increased due to salt water intrusion of oil-based drilling fluid.At 20%salt water intrusion,the viscosity decreased from 118 mPa·s to 96 mPa·s.At 30%salt water intrusion,the viscosity began to rise,and at 50%salt water intrusion,the viscosity exceeded the range of the viscometer.The emulsion-breaking voltage decreased gradually.When the salt water intrusion amount increased from 0 to 60%,the emulsion-breaking voltage drops from 468 V to 90 V.When the salt water intrusion was less than 10%,it was recommended to maintain normally and supplement appropriate main and auxiliary emulsifiers.When the salt water intrusion amount was 10%—30%,it was suggested that the drilling fluid should be separately treated and appropriate diesel oil and treating agent should be supplemented.When the salt water intrusion amount was above 30%,it is recommended to collect and treat drilling fluid on the ground.The reasonable choice the drilling fluid maintenance program was conducive to reducing the probability of occurrence of complex downhole conditions.