地层岩石可钻性的分形表示方法

石油钻井中测量岩石可钻性的主要方法是以井下取心为对象来测量岩石的力学性能和进行微钻法可钻性试验,但这种方法采样费用高,试验周期长,不能在现场直接应用.对石油钻井过程中岩石破碎的分形机理及形成过程进行了研究,提出了一种以井底返出的岩屑为对象测试岩石可钻性的新方法.在室内实验基础上,确定了不同井深岩石破碎后的块度分布函数,计算了岩石破碎的分形维数,分形维数的相关性系数在0.95以上.结合岩石硬度、强度和可钻性级值的实验结果,确定了岩石强度、硬度及可钻性与岩石分形维数的统计模型.

Fractal representation of rock drillability

The traditional method for measuring drillability and mechanical properties of rock has the disadvantages of high cost sampling and long-period testing and is indirectly and difficult in field application. A new method for testing rock drillability is presented. This method takes the detritus returned from bottom hole as the studying object. The fractal mechanism and forming process of broken rock during drilling were studied. The fragment distribution function of broken rock gained from the different depth of well was determined on the basis of laboratory experiment. The fractal dimension of broken rock was calculated. The correlation coefficient of fractal dimension is above 0. 95. According to the experimental results of rigidity, intensity and drillability of rocks, a statistical model for combining rigidity, intensity and drillability of rocks with fractal dimension of fragment can be determined.