A CORE-BASED METHOD TO DETERMINE THREE-DIMENSIONAL IN-SITU STRESS IN DEEP DRILLING WELLS:ANELASTIC STRAIN RECOVERY TECHNIQUE
基于岩芯非弹性应变恢复量测定的深孔三维地应力测试方法

There is no foolproof method by which the magnitudes and orientations of three-dimensional in-situ stresses can be reliably measured at great depths,although various field and laboratory measurement techniques have been proposed. In the case of scientific deep-drilling wells,therefore,it is desirable to combine borehole methods with core-based methods to obtain a complete three-dimensional in-situ stress. Here,the principles,testing techniques,and procedures for a new and effective core-based stress measurement method called anelastic strain recovery (ASR) technique are described;and then its application to a scientific deep-drilling project is shown. The measurement results reveal that the method is suitable for determining the orientations of the principal stresses and for estimating their magnitudes in deep drilling wells where other methods such as the over-coring technique and hydraulic fracturing tests are difficult or impossible to be conducted,or are needed complementary data to enhance the reliability of the stress measurements.