深层地应力测量新方法

实验研究了深部地层岩芯的声波速度各向异性及在恢复加载条件下的声发射Kaiser效应，提出了一种简便的深部地层地应力测量新方法。全尺寸岩芯被钻取后，其应力卸载的各向异性导致声波速度各向异性，利用这一原理可确定水平最大、最小地应力的相对位置，对上述位置岩芯进行取样，进行围压下的声发射Kaiser实验，就可测量出水平主地应力大小。该方法一则解决了一直困扰Kaiser实验的对岩芯完整性高标准要求的问题，二则完善了超深井地层的地应力测试方法，同时，为超深井水力压裂设计和维持井壁稳定的安全泥浆密度确定提供了最重要的参数。

NEW METHOD FOR MEASUREMENT OF IN-SITU STRESSES AT GREAT DEPTH

A new method is presented for measurement of in-situ stresses at great depth,which is based on the experimental research on anisotropy of acoustic velocity and Kaiser effect of acoustic emission for deep formation cores. The different magnitude of acoustic velocity around the surface of core cylinder is caused by the different degree of unloading on the core. The magnitude of acoustic velocity is the minimum in the direction of maximum in-situ stress,and the maximum in the direction of minimum stress. Based on this principle,the relative position of the maximum and minimum horizontal principal in-situ stresses can be determined. Then the acoustic emission experiments are performed on the two core samples drilled from the certain position,and the horizontal in-situ stress state is determined. The advantage of this method is that the experiment can be performed on thin layer core instead of an integral core of 15 cm long without any fracture,and can improve measurement of in-situ stresses at great depth.