As the cap rock for oil and natural gas traps, tight shale with small interstitial spaces and invisible beddings were found to have large reserves and rich mining value. Precise identification of feature anisotropy in tight shale is of significance in the development of petroleum reservoirs. Here in this work, we demonstrate an application of a 532-nm laser to measure the lateral photovoltaic (LPV) response of a tight shale with the beddings invisible at different directions inside the upper surface. Although the layer orientations were not obviously for the tight shale, anisotropic response of LPV signals was observed with different peak amplitudes (Vp) as well as lateral and surface distributions. The bedding direction revealed by SEM was consistent with the LPV test results; meanwhile, a trigonometric angular-dependent Vp was observed, proving that the LPV measurements were able to predict the configuration orientation of tight shale with invisible beddings. Our results proved that the lateral photovoltaic response is sensitive to the structure of materials and thus has a great potential in the characterization of shale reservoirs.

中文翻译：

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隐形层理致密页岩各向异性响应的横向光伏探测

作为油气圈闭的盖层，发现孔隙小、隐蔽层理的致密页岩储量大，具有丰富的开采价值。致密页岩特征各向异性的精确识别对油气藏开发具有重要意义。在这项工作中，我们展示了应用 532 nm 激光测量致密页岩的横向光伏 (LPV) 响应，在上表面内的不同方向上看不到层理。虽然致密页岩的层位取向不明显，但观察到 LPV 信号的各向异性响应具有不同的峰值幅度 (Vp) 以及横向和表面分布。SEM显示的层理方向与LPV测试结果一致；同时，观察到三角角度相关的 Vp，证明 LPV 测量能够预测具有隐形层理的致密页岩的构造方向。我们的研究结果证明横向光伏响应对材料的结构很敏感，因此在页岩储层的表征中具有很大的潜力。