Determination of three dimensional in situ stress from core discing based on analysis of principal tensile stress
Determination of three dimensional in situ stress from core discing based on analysis of principal tensile stress
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DOI：
10.1016/j.ijrmms.2004.05.002
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发表时间：
2004-10
影响因子：
7.2
通讯作者：
K. Matsuki;N. Kaga;T. Yokoyama;N. Tsuda
中科院分区：
文献类型：
--
作者：
K. Matsuki;N. Kaga;T. Yokoyama;N. Tsuda
为了确定岩心盘的所有地应力分量，必须确定给定厚度的盘的主地应力的方向和大小。在这项研究中，我们分析了11个核心长度的HQ核心短柱下的拉伸应力的方向和大小，使用的应力条件下，核心盘可能会发生。首先，基于对芯柱下方的拉应力方向的分析，我们提出了一种从圆盘端面周边的高度分布确定原地应力方向的方法。该方法可用于任何厚度的盘。其次，基于对岩心中心拉应力大小的分析，提出了适用于任意长度岩心的岩心盘裂线性判据。这个标准是在良好的协议与经验公式先前在实验室实验中获得的。在垂直应力由上覆岩层应力给出的假设下，将地应力方向信息与岩心圆盘线性判据相结合，提出了一种由岩心圆盘确定地应力各分量的方法。最后，将这些方法应用于从进行水力压裂以测量水平应力的现场获得的圆盘。结果表明，岩心圆盘法估算的主应力方位角与水力压裂法测定的主水平应力方位角一致，而岩心圆盘法估算的主水平应力幅值离散较大，但与水力压裂法测定的主水平应力幅值相似。
To determine all of the components of in situ stress from core discing, both the directions and magnitudes of the principal in situ stresses must be determined for a disc of a given thickness. In this study, we analyzed the direction and magnitude of tensile stress below an HQ core stub for 11 core lengths using stress conditions under which core discing is likely to occur. First, based on an analysis of the direction of tensile stress below the core stub, we propose a method for determining directions of in situ stress from the height distribution at the periphery of the end surface of a disc. This method can be used with a disc of any thickness. Next, based on an analysis of the magnitude of tensile stress in the central part of a core, we propose a linear criterion for core discing, which can be applied to a core of any length. This criterion was in good agreement with an empirical formula obtained previously in laboratory experiments. By combining information on the direction of in situ stress and the linear criterion for core discing, we propose a method for determining all of the components of in situ stress from core discing under the assumption that vertical stress is given by the overburden stress. Finally, these methods were applied to discs obtained from a field where hydraulic fracturing was performed to measure horizontal stresses. The results showed that the azimuths of the principal stresses estimated from core discing were consistent with those of the principal horizontal stresses determined by hydraulic fracturing and that while the magnitudes of the principal horizontal stresses estimated from core discing showed a large scatter, they were similar to those determined by hydraulic fracturing.