DEVELOPMENT OF BOREHOLE ACOUSTIC EMISSION SONDE TO DETERMINE CRACK DIRECTION OF HYDRAULIC FRACTURING

在用于应力测量的水力压裂中，由压裂引起的裂缝方向遵循最大压应力的方向。为了识别方向，通常在水力压裂后取出探头，然后将另一个探头插入井眼，获得裂缝的痕迹。因此，当井眼变深时，这种方法需要很长时间。为了解决这一问题，我们提出了对水力压裂过程中的声发射事件进行测量并确定裂缝方向的设想。我们研制了一种测试探头，在垂直于探头轴线的横截面上安装了四个声发射传感器。利用该探头对确定裂纹方向的可行性进行了研究。结果表明，该探头具有一定的实用价值，并对探头进行了改进。

In hydraulic fracturing for stress measurement, the direction of cracks due to fracturing follows the direction of the maximum compressive stress. To identify the direction, the sonde is usually removed after hydraulic fracturing, and then the other sonde is inserted into the borehole and traces of the cracks are obtained. Thus, this method takes a lot of time when a borehole becomes deep. To solve the problem, we get an idea to measure AE (Acoustic Emission) events accompanied with hydraulic fracturing and determine the crack direction. We developed a test sonde mounting four AE sensors in a cross section normal to the axis of the sonde. Using the sonde, the feasibility in determination of the crack direction is investigated. It is found that the sonde could be used practically with some improvements clarified from this investigation.