一种预测钻井液产生泥球的室内实验方法

钻遇某些软泥岩地层时，钻井液上返过程中易形成泥包现象。为了预测钻井过程中所采用的钻井液是否会产生泥球，通过评价钻井液性能的常用设备，利用含水岩屑颗粒和一定粒径的钢球以及滚动老化模拟在井下岩屑随流体运动的过程，提出了具体的实验参数，建立了一种系统评价泥球产生情况的方法。实验结果表明，该方法可以对不同类型的钻井液在即将使用的过程中泥球产生情况进行预测。实验结果与现场实况相符，得到所试用的水基体系易产生泥球的条件为:滚动时间为20 min，目标温度为90℃；所试用油基体系易产生泥球的条件为:滚动时间为30 min，目标温度为120℃；同时该方法得到的实验结果还可作为优化钻井液性能的依据，提高钻井过程中的作业效率和安全性。 

A Laboratory Test Method for Predicting Mud Ball Generation in Drilling Fluids

When drilling soft mudstones, mud ball will be generated in the drilling fluid flowing upwards in the annulus. To predict the generation of mud balls in a drilling fluid, an evaluation procedure with test parameters was established using drilling fluid measuring apparatus. In the procedure, drilled cuttings containing water and steel balls are mixed together and tested on a hot rolling tester (to simulate the flow of cuttings downhole). Using this procedure, some drilling fluids were tested. Test results showed that this procedure is feasible in predicting the generation of mud balls in several kinds of drilling fluids. The test results conformed to what were observed in field operations. In laboratory test, it was found that conditions for a water base drilling fluid to generate mud balls during drilling were as follows:hot rolling at 90℃ for 20 min. the conditions for an oil base drilling fluid to generate mud balls were:ht rolling at 120℃ for 30 min. Experimental results obtained from this procedure can be used as a base on which drilling fluid is optimized for high efficiency and safe drilling operation.