水平定向钻穿越施工中钻井液渗透对孔壁塑性半径的影响

以大直径水平定向钻进(HDD)在实际砂土层的工况为对象,通过理论分析和实验室测试的方法推导HDD钻孔孔壁的塑性半径的计算公式,并对试验测试结果进行分析。结果表明:当压差等于零或内压大于外压时,孔壁塑性半径受到钻井液渗透的影响非常小,几乎趋近于一个定值;当内外压差小于1.0 MPa时,塑性半径受钻井液渗透影响程度呈指数增加,当内外压差大于1.0 MPa时,其理论值已经超过了实际工程钻井液渗透的半径。

Effect of drilling fluid penetration on plastic radius of horizontal directional drilling borehole

Based on the field data of horizontal directional drilling (HDD) project, theory analysis and sample testing were used to deduce calculation formula of plastic radius in HDD borehole. The testing results were analyzed. The results show that, when the pressure difference is zero or ground pressure is larger than slurry pressure, plastic radius tends to be a constant with little change. When pressure difference is less than 1.0 MPa, plastic radius increases exponentially with the increment of drilling fluid penetration. When pressure difference is more than 1.0 MPa, plastic radius shows an exaggerated range beyond the penetration radius.