CO2在钻井液中的溶解度实验及规律研究

Solubility Experiment and Law Study of CO2 in Drilling Fluid

深水钻井气侵期间,受大温度差环境的影响,井筒内钻井液流动过程中会发生气体的溶解与脱溶,对于溶解度较大的CO 2气体更是如此。准确预测钻井液体系中CO 2的溶解规律,是井筒多相流动计算、溢流早期监测以及井筒压力控制等关键问题的基础内容。本文以溶解度实验为基础,构建了高温高压气体溶解度测量实验系统,在25~84℃、5~45 MPa温度压力范围内,对CO 2在水基钻井液体系内的溶解度进行了测量,结果表明:①温度一定时,随着压力的升高,溶解度逐渐变大,但变化趋势逐渐变缓;②一定的温度压力下,CO 2在KCl、NaCl水溶液中的溶解度随着离子浓度的增加,溶解度逐渐降低;③聚合物处理剂对CO 2的溶解度影响不大;④对于钻井液这一复杂体系而言,CO 2的溶解度主要受到无机盐的影响,较高的无机盐浓度导致CO 2的溶解度比在纯水中的小。

During deep water drilling,due to the influence of large temperature difference environment,gas dissolution and desolvation will occur during the drilling fluid flow in the wellbore,especially for the more soluble CO 2 gas.Accurate prediction of CO 2 dissolution in drilling fluid systems is the basic content of key issues such as wellbore multiphase flow calculation,early overflow detection and wellbore pressure control.Based on the solubility experiment,a high temperature and high pressure gas solubility measurement experimental system was constructed.The solubility of CO 2 in water-based drilling fluid system was measured in the temperature range of 25~84℃and 5~45 MPa.The results show that:①When the temperature is constant,the solubility gradually increases with the increase of pressure,but the change trend gradually becomes slower;②Under certain temperature and pressure,the solubility of CO 2 in KCl and NaCl aqueous solution is gradually reduced with the increases of the concentration of ions;③The polymer treatment agent has little effect on the solubility of CO 2;④For the complex system of drilling fluid,the solubility of CO 2 is mainly affected by inorganic salts,and the higher inorganic salt concentration leads to the solubility of CO 2 compared to that in pure water.