超临界CO2压裂对储层渗透率的适应性研究

Study on Adaptability of Supercritical CO2 Fracturing on Reservoir Permeability

  • 摘要: 为探究超临界CO2压裂对储层渗透率的适应性,采用不同渗透率(0.08~1.0 mD)致密砂岩岩样的超临界CO2压裂实验结合CT扫描技术定量分析了压裂诱导裂缝特征,并采用矿场尺度数值模拟对实验结果进行验证与补充。实验结果表明:超临界CO2可有效压裂渗透率在0.08~0.3 mD范围内的岩样,且随着渗透率增加,诱导裂缝复杂度降低,裂缝体积减小;当渗透率超过0.5 mD时,超临界CO2无法实现岩石压裂,但水压裂仍可有效压裂,这主要归因于流体性质的差异。数值模拟结果验证了实验结论,表明在矿场施工条件下,超临界CO2可成功压裂不同渗透率储层,但压裂效果存在显著差异。随着储层渗透率增加(0.01~100 mD),裂缝半长、缝宽、缝高、分形维数及渗滤面积等参数均呈下降趋势,而滤失量逐渐增加,导致压裂效果逐渐变差。超临界CO2更适用于低渗透率储层改造,在施工过程中需针对不同渗透性储层进行参数优化。该研究为超临界CO2压裂非常规储层的施工方案设计提供了理论依据。

     

    Abstract: To investigate the adaptability of supercritical CO2 fracturing to reservoir permeability, this study conducted supercritical CO2 fracturing experiments on tight sandstone samples with different permeabilities (0.08~1.0 mD). The characteristics of induced fractures were quantitatively analyzed using CT scanning, and the experimental results were validated and supplemented through field-scale numerical simulations. The results show that supercritical CO2 can effectively fracture rock samples with permeabilities in the range of 0.08~0.3 mD. As permeability increases, the complexity of induced fractures decreases, and the fracture volume reduces. When the permeability exceeds 0.5 mD, supercritical CO2 fails to fracture the rock, whereas hydraulic fracturing remains effective, primarily due to differences in fluid properties. Numerical simulations validated the experimental findings, indicating that supercritical CO2 can successfully fracture reservoirs with different permeabilities under field conditions, but the fracturing effectiveness varies significantly. As reservoir permeability increases (0.01~100 mD), parameters such as fracture half-length, width, height, fractal dimension, and filtration area decrease, while fluid loss gradually increases, leading to a decline in fracturing effectiveness. The study demonstrates that supercritical CO2 is more suitable for low-permeability reservoir stimulation, and parameter optimization is required during operations to adapt to reservoirs with different permeabilities. This research provides a theoretical foundation for the design of supercritical CO2 fracturing operations in unconventional reservoirs.

     

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