气体钻井的岩屑特征及粒度分布测试

气体钻井因其独特的钻井工艺和优势，正在成为我国油气田勘探开发的主导技术之一。现场调研表明：与常规钻井液钻井相比，气体钻井中钻具的冲蚀磨损和断裂尤其突出，造成钻具过早降级和报废，钻井事故井数占总井数的77.8%。钻具的冲蚀磨损除与钻井工艺参数有关，还与岩屑的基本属性如粒径大小及其分布、形状、硬度等密切相关。采用筛分法对气体钻井的岩屑粒径分布进行了测定，得到了岩屑粒径分布的直方图，通过计算得到普光103-4井的岩屑平均粒径为1.05 mm，大邑3井的岩屑平均粒径为0.26 mm。岩屑的形状与钻井参数有关，空气锤破碎岩石的岩屑形状呈不规则片状，牙轮钻头破碎岩石的岩屑形状呈纺锤形。

CHARACTERISTICS OF GAS DRILLING CUTTINGS AND GRAIN SIZE DISTRIBUTION DETERMINATION

Gas drilling is becoming the leading technology in oilfield exploration and development in China due to its unique drilling procedures and advantages.The field investigation indicates that the drilling tool erosion and fracture is rather common during gas drilling when compared with conventional drilling fluid.That will cause early degradation and rejection of drilling tools,making wells with accidents amount about 77.8% of the total wells drilled.The drilling tool erosion is related with the grain size,grain distribution,shape and hardness of the drilling cuttings in addition to the drilling parameters.The Screen Method has been adopted to determine the grain size distribution of gas drilling cuttings,a corresponding histogram is then developed.Through calculation by the histogram it is found that the average cuttings size is 1.05 mm on the well Puguang 103-4,and 0.26 mm on the well Dayi-3.The shape of cuttings is related with the drilling parameters.The cuttings often appear in irregular flakes during air hammer drilling,and in spindle shape during cone bit drilling.