深层碳酸盐岩岩相与力学性质相关性特征及成因机制

Correlation characteristics and genetic mechanisms between lithofacies and mechanical properties of deep carbonate rocks

  • 摘要: 为深入剖析深层碳酸盐岩岩相特征与力学性质之间的内在联系,以塔里木盆地塔河地区奥陶系鹰山组为研究对象,综合运用钻井岩心、岩石薄片及岩石力学实验测试等资料,明确碳酸盐岩的岩相类型,应用Image J软件定量表征岩石的组分,揭示了不同岩相与岩石力学性质的相关性。塔河地区鹰山组碳酸盐岩的3种主要岩相为亮晶颗粒灰岩、细—中晶白云岩和泥晶颗粒灰岩,通过实验测试发现不同岩相的岩石力学性质存在显著差异,表现为细—中晶白云岩的抗压强度、杨氏模量、纵波速度和横波速度最高,而泥晶颗粒灰岩和亮晶颗粒灰岩的相应参数依次降低;泥晶颗粒灰岩的泊松比最高,而亮晶颗粒灰岩最低。此外,建立了岩相与岩石力学的3个线性方程的多元回归模型,其中模型2相关性最优(R2=0.777);并揭示了不同岩相的岩石力学性质差异性的成因机制。颗粒尺寸和胶结物含量控制着岩石的力学特性,即颗粒灰岩中纵波和横波速度随着颗粒尺寸增大而减小,对应的抗压强度降低;而随着胶结物含量的增加,横、纵波速度显著降低,颗粒尺寸与胶结物含量之间呈线性函数关系。该研究有望通过岩相精细分析来预测深层碳酸盐岩的岩石力学特性,从而深化油气地质—工程一体化进程。

     

    Abstract: To deeply analyze the intrinsic relationship between lithofacies characteristics and the mechanical properties of deep carbonate rocks, the study focuses on the Ordovician Yingshan Formation in the Tahe area of the Tarim Basin. Drilling cores, rock thin sections, and rock mechanics experimental data were comprehensively analyzed to clarify the lithofacies types of the carbonate rocks. Rock components were quantitatively characterized using ImageJ software, and the correlations between different lithofacies and rock mechanical properties were revealed. Three main carbonate rock lithofacies were identified in the Yingshan Formation of the Tahe area: sparry grained limestone, fine-medium crystalline dolomite, and micritic grained limestone. Experimental results revealed significant differences in rock mechanical properties among these lithofacies. Specifically, the fine-medium crystalline dolomite exhibited the highest compressive strength, Young's modulus, and compressional and shear wave velocities, while the corresponding parameters of the micritic and sparry grained limestones decreased successively. The micritic grained limestone had the highest Poisson's ratio, while the sparry grained limestone had the lowest. Additionally, multiple regression models with three linear equations were developed to describe the relationships between lithofacies and rock mechanics, among which Model 2 achieved the best correlation (R2=0.777). The study elucidated the genetic mechanisms underlying the variations in rock mechanical properties across different lithofacies. Grain size and cement content were the main controlling factors. The compressional and shear wave velocities of grained limestone decreased with increasing grain size, accompanied by a corresponding decrease in compressive strength. In contrast, as cement content increased, the shear and compressional wave velocities significantly decreased, and a linear functional relationship was observed between particle size and cement content. The study is expected to predict the mechanical properties of deep carbonate rocks through detailed lithofacies analysis, thereby advancing the geological and engineering integration process of oil and gas production.

     

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