井眼扩径对水平井声波测井响应影响的数值模拟

水平钻井得到越来越广泛的应用。作为储层评价最重要手段之一的声波测井在水平井中往往受到井眼状况等因素的影响,从而导致其应用效果明显变差。为此,采用三维有限差分法针对径向扩径尺寸变化、轴向扩径尺寸变化和扩径位置变化三大类情况开展了正演模拟研究,重点研究了井眼扩径对水平井声波测井波形幅度、到时和波速的影响。结果表明,当扩径段位于声源与最近的接收器之间时,扩径属性参数变化对纵横波波速测量结果无影响,但均会导致波形幅度明显降低;纵、横波幅度均随扩径圆筒厚度和长度的增大而减小,但基本不受扩径距的影响;纵波到时随扩径圆筒厚度和长度的增大而增大,但随扩径距的增大而轻微减小。本研究厘清了井眼扩径对水平井声波测井响应的影响规律,可为进一步开展水平井声波测井影响因素校正方法研究提供指导和帮助。

Numerical simulation of the effects of borehole enlargement on sonic logging response of horizontal wells

Horizontal well drilling is increasingly being widely applied. However, sonic logging-one of the most important reservoir assessment methods-tends to be affected by the borehole conditions in the application of horizontal wells,leading to notably reduced application effects.In view of this fact,this paper conducts the forward simulation of the radial and axial size changes induced by borehole enlargement and the changes in enlargement positions using the three-dimensional finite difference method,with the focus on the effects of borehole enlargement on the waveform amplitude,arrival times,and velocities of waves in the sonic logging of horizontal wells.The results are as follows.In the case that the borehole enlargement occurred between the sonic transmitter and the nearest receiver,the changes in borehole enlargement parameters had no effect on the measured results of the compressional and shear wave velocities but led to the notable decrease in waveform amplitude.The amplitude of compressional and shear waves decreased with an increase in the thickness and length of the enlargement cylinder but was almost not affected by the distance between the sonic transmitter and the expansion section.The compressional wave arrival time increased with an increase in the thickness and length of the enlargement cylinder but slightly decreased with an increase in the distance between the sonic transmitter and the expansion section.This study clarifies the laws of the effects of borehole enlargement on the sonic logging response of horizontal wells,and it will provide guidance and assistance for further research on the methods for influencing factor correction in the sonic logging of horizontal wells.