用声波法评价地层可钻性各向异性的实验研究

地层可钻性各向异性的评价对井眼轨迹控制具有重要意义。通过室内实验分别测定了岩芯垂直于和平行于地层层面方向的可钻性及声波速度，得到了岩石可钻性各向异性指数和波速各向异性系数，并对结果进行了讨论。用数理统计方法研究分析了牙轮钻头岩石可钻性各向异性指数、牙轮钻头垂直于和平行于地层层面方向岩石可钻性差值和PDC钻头岩石可钻性各向异性指数与纵波波速各向异性系数的相关关系，建立了用纵波波速各向异性系数评价地层可钻性各向异性的模型。利用所建立的模型，采用地震资料或测井资料可以方便地对地层可钻性各向异性进行评价。对河南油田AN2004井进行评价，其结果表明，用该方法评价出的地层可钻性各向异性能正确反映被评价地层的特性。

EXPERIMENTAL STUDY ON EVALUATION OF FORMATION DRILLABILITY ANISOTROPY BY ACOUSTIC WAVE VELOCITY

The evaluation of drillability anisotropy of the formation is very important for well trajectory control.The velocities of ultrasonic wave and rock drillability are measured in perpendicular and parallel directions of the bedding plane of core samples which were cut from the approach hole of Chinese continental scientific drilling.Rock drillability index and P-wave velocity anisotropy coefficient are calculated from the testing data;and the results are discussed.Correlation of drillability anisotropy index of the roller cone bit and PDC bit,the difference between drillability of the roller cone bit in perpendicular and horizontal directions of the bedding plane with the P-wave velocity anisotropy coefficient are studied respectively by means of mathematical statistics.A mathematical model is established for predicting drillability anisotropy index by using P-wave velocity anisotropy coefficient.Thus,drillability anisotropy of a formation can be evaluated conveniently from seismic or logging data by using this model.The method is used to evaluate drillability anisotropy of a formation of Well AN2004 in Henan Oilfield in China.The result shows that the formation drillability anisotropy index predicted by using this method can properly reflect the deviation characteristics of the formation being evaluated.