基于空心球破碎概率的双梯度钻井井筒压力预测

Prediction of wellbore pressure in dual-gradient drilling based on the breaking probability of hollow glass spheres

张锐尧,李军,柳贡慧,郝希宁,何玉发,周云健,王宁

中国石油大学（北京），北京 102249 中国石油大学（克拉玛依），新疆 克拉玛依 840000 北京工业大学，北京 100022 中海油研究总院有限责任公司，北京 100028 中国石油塔里木油田分公司，新疆 库尔勒 841000）

为了研究注空心球双梯度钻井过程中空心球破碎对井筒压力分布的影响，首先，利用分形强度理论与碰撞动力学，建立了空心球在钻井循环过程中的碰撞破碎概率模型，研究了在钻柱内、分离器内部、分离口及环空中的破碎概率分布规律；然后，利用双梯度钻井室内模拟实验系统，研究了过滤分离器在不同排量及空心球注入体积分数时的分离效率；最后，结合碰撞破碎概率模型与分离效率，建立了空心球破碎条件下的深水双梯度钻井井筒压力预测模型，结合钻井数据进行了数值计算和敏感性分析，同时利用室内实验对井筒压力预测模型进行了验证。结果表明：随着排量增加，空心球破碎概率逐渐增加，在分离器内及分离口处破碎概率较大；空心球的破碎概率、破碎数量及分离器位置等都会对井筒压力及钻井液密度产生显著影响。该研究可提高井筒压力预测的精度，降低因空心球破碎导致的钻井风险。

 In order to study the impact of hollow glass spheres (HGS) breaking on wellbore pressure distribution during dual-gradient drilling by HGS injection, the fractal strength theory and collision dynamics were used to establish the probability model of the collision and breaking of the HGS during the drilling circulation, and the distribution law of breaking probability inside the drill string, the separator, the separation port, and the annulus were studied respectively. Then, the indoor simulation experiment system for dual-gradient drilling were used to study the separation efficiency of the filter separator at different displacements and hollow ball injection volume fraction. Finally, combining the collision breaking probability model and the separation efficiency, the wellbore pressure prediction model during deep-water dual-gradient drilling under the condition of HGS breaking was established, and numerical calculation and sensitivity analysis were carried out based on the drilling data. At the same time, the wellbore pressure prediction model was verification by laboratory experiments. The results show that the probability of HGS breakage gradually increases with the increase of pump flow rate, and the breaking probability inside the separator or at the separation port is greater. The breaking probability of the HGS, the number of the broken HGS and the separator location will affect the distribution of wellbore pressure and drilling fluid density obviously. This research can further improve the accuracy of wellbore pressure prediction and reduce the drilling risk caused by the broken HGS.

10.6056/dkyqt202202024