Experimental Quantification of the Evolution of the Static Mechanical Properties of Tight Sedimentary Rocks during Increasing-amplitude Load and Unload Cycling
Experimental Quantification of the Evolution of the Static Mechanical Properties of Tight Sedimentary Rocks during Increasing-amplitude Load and Unload Cycling
复制标题
增幅加载和卸载循环过程中致密沉积岩静态力学性质演化的实验量化
DOI：
10.1190/geo2021-0232.1
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发表时间：
2021-12
期刊：
影响因子：
3.3
通讯作者：
Jianhua Geng
中科院分区：
文献类型：
--
作者：
Wang Yang;Zhao Luanxiao;Han De-hua;Wei Qianqian;Zhang Yonghao;Yuan Hemin;Jianhua Geng
了解致密储层岩石的线性和非线性弹性行为对于油气勘探和生产、温室气体地质储存和地热能开发中的许多地球物理和地质力学应用至关重要。本文对三种致密沉积岩进行了一系列三轴加卸载循环试验，探讨了其静态力学性质（杨氏模量和泊松比）的变化规律。我们打算描绘的过渡，从线性到非线性弹性结合静态测量与动态测量。实验结果表明，静态力学性能增加加载应力循环，但在卸载应力循环下降。在增加幅度的卸载循环时，静态机械性能逐渐从接近动态性能的值降低到接近负载循环时的静态性能的值。通过二次拟合静态力学性质与卸载循环过程中应变幅的函数关系，定义了一个约为5 × 10−5的特征应变幅，以区分三种致密岩石的线性弹性主导和非线性弹性主导行为。致密沉积岩中的这种过渡行为可以从微观上解释为从循环应力卸载开始摩擦控制滑动的逐渐激活。这些观察结果为致密沉积岩在实验室静态测量过程中从线性弹性向非线性弹性转变提供了直接的实验证据，这将有助于理解动静参数相关性以及地球科学或地球工程应用中岩石变形的建模。
Understanding the linearly and nonlinearly elastic behaviors of tight reservoir rocks is crucial for numerous geophysical and geomechanical applications in hydrocarbon exploration and production, geological repositories for greenhouse gases, and geothermal energy exploitation. We perform a suite of triaxial load and unload cycling tests with increasing stress amplitudes on three tight sedimentary rocks to explore the evolution of their static mechanical properties (Youngs modulus and Poissons ratio). We intend to depict the transition from linear to nonlinear elasticity by combining static measurements with dynamic measurements. The experimental results suggest that static mechanical properties increase upon load stress cycling but decrease upon unload stress cycling. Upon the increasing-amplitude unload cycling, static mechanical properties gradually decrease from values approaching dynamic properties to values closer to static properties upon load cycling. By quadratically fitting the static mechanical properties as functions of the strain amplitude in the process of unload cycling, we define a characteristic strain amplitude of about 5 × 10−5 to distinguish the linearly elasticity-dominated and nonlinearly elasticity-dominated behaviors for three tight rocks. Such transitional behavior in tight sedimentary rocks can be microscopically explained by the gradual activation of friction-controlled sliding from the beginning of the cyclic stress unload. These observations provide direct experimental evidence of the transition from linear to nonlinear elasticity for tight sedimentary rocks during the laboratory static measurements, which will facilitate understanding of the dynamic-static parameter correlation and the modeling of rock deformations in geoscience or geoengineering applications.