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    汶口凹陷盐穴储能库地质−地球物理特征研究

    Geological and geophysical researches of salt cavern for energy storage in the Wenkou sag

    • 摘要: 为精准预测不规则盐穴的形态、稳定性和密闭性,支撑盐穴压缩空气储能工程建设,建立了盐穴储能库地质、地球物理特征综合评价流程。该流程通过精细构造解释评价盐穴区域的构造稳定性;利用目标概率反演预测盐岩及夹层分布;在地震正演模拟的基础上,运用多属性联合分析和三维地质体雕刻定量预测盐穴形态及有效体积;最后对盐穴取心开展微观特征分析,验证盐穴盖层的封闭能力。将该流程应用于汶口凹陷废弃盐穴的地质评价,结果表明:盐穴2 km范围内几乎无大型断裂发育,盐层总厚度大于60 m,含盐地层中的盐岩占比约为50%;其中,1号至5号盐层在全区发育稳定,与膏盐互层分布,顶、底板地层均为致密岩性。通过地震正演建立了盐穴地震相模式,其腔体顶界为上凸的强振幅反射,底界为下凹的弱振幅反射,两侧可见地震同相轴错断。初步选取了瞬时振幅、纹理、边缘检测、相干能量梯度等4种敏感属性,结果显示1井、4井和5井盐穴相对独立发育,而2井与3井盐穴之间发育连接通道。边缘检测属性的刻画效果最优,在此基础上采用“阈值分割法”刻画三维盐穴形态,预测体积与采盐量折算结果和井数据吻合良好,误差率仅为0.76%。对盐穴取心开展微观结构、孔隙度和渗透率、突破压力、扩散系数测试,进一步验证了盐穴盖层具有较强的封闭能力。综上所述,研究区盐穴构造背景稳定,储集空间较大,密闭性较强,具备建设压缩空气储能库的地质条件。

       

      Abstract: To accurately predict the morphology, stability, and sealing capacity of irregular salt caverns and support their application in compressed air energy storage, this study establishes a comprehensive geological and geophysical evaluation process for salt cavern reservoirs. Through detailed structural interpretation, the tectonic stability of salt cavern regions is assessed. Target probability inversion is employed to predict the distribution of salt rock and interlayers. Based on seismic forward modeling, multi-attribute joint analysis and 3D geological body carving are used to quantitatively predict salt cavern morphology and effective volume. Finally, microscopic characteristic analysis of salt cavern core samples is conducted to verify the sealing capacity of the cavern roof. The results indicate that the saline formation has a gentle dip, with only small-scale fractures developing in the deep section and no fractures within a 2km plane. The total salt layer thickness exceeds 60m, with a salt-to-ground ratio of approximately 50%. Among these, salt layers 1 to 5 are stably developed across the entire area, interbedded with gypsum-salt layers, while both the roof and floor formations consist of dense lithologies. A seismic facies model for salt caverns is established, featuring an upward-convex strong amplitude reflection at the top boundary, a downward-concave weak amplitude reflection at the bottom boundary, and seismic events discontinuities on both sides. Four sensitive attributes—instantaneous amplitude, texture, edge detection, and coherence energy gradient—are preliminarily selected, revealing relatively independent salt cavern development in wells 1, 4, and 5, while connecting channels exist between the salt caverns in wells 2 and 3. The edge detection attribute demonstrates optimal characterization performance, and based on this, the "threshold segmentation method" is used to delineate the 3D morphology of salt caverns. The predicted volume aligns with the converted salt extraction data and well records, with an error rate of only 0.76%. Further verification of the strong sealing capacity of salt cavern roofs is conducted through microscopic structure, porosity and permeability, breakthrough pressure, and diffusion coefficient tests on salt cavern core samples. In summary, the salt caverns in the study area exhibit stable tectonic conditions, considerable storage space, and strong sealing capacity, meeting the geological requirements for constructing compressed air energy storage facilities.

       

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