基于分形理论的页岩基质表观渗透率研究

发布时间：2018-12-14 21:13

【摘要】：为了表征页岩基质表观渗透率,研究其动态变化规律,基于迂曲毛细管束分形理论及气体微观渗流机理,分别建立考虑吸附、滑脱、扩散及渗流的无机质和有机质表观渗透率模型,并通过面积系数加权得到页岩基质表观渗透率模型。结合实验数据及已有模型验证了新建模型的可靠性,定量分析了页岩基质微观孔隙结构(孔径、孔隙度、分形维数),外界环境(压力、含水饱和度、有效直径修正因子)及气体性质对页岩基质表观渗透率的影响。研究结果表明:随着储层压力的降低,无机质孔隙水膜厚度增大,有效直径减小,迂曲度分形维数增大,孔隙分形维数减小,气体滑脱效应增强,但仍以吸附影响为主,无机质表观渗透率总体呈下降趋势;有机质孔隙吸附气解吸使有效直径修正因子逐渐增大,迂曲度分形维数减小,孔隙分形维数增大,滑脱效应及努森扩散在低压小孔中增强,有机质表观渗透率总体呈上升趋势;有机质与无机质表观物性参数随压力、吸附层变化规律不同,渗透率差值较大,因此在页岩基质表观渗透率研究时应予以区分计算,避免其差异性所带来的误差。
[Abstract]:In order to characterize the apparent permeability of shale matrix and study its dynamic variation, based on the fractal theory of tortuous capillary bundles and the mechanism of gas microscopic seepage, the adsorption and slippage were established, respectively. The apparent permeability model of inorganic and organic matter is obtained by diffusion and percolation, and the apparent permeability model of shale matrix is obtained by weighted area coefficient. The reliability of the new model is verified by combining the experimental data and the existing models. The micropore structure (pore size, porosity, fractal dimension), external environment (pressure, water saturation) of shale matrix are quantitatively analyzed. Effect of effective diameter correction factor and gas properties on the apparent permeability of shale matrix. The results show that with the decrease of reservoir pressure, the thickness of inorganic pore water film increases, the effective diameter decreases, the fractal dimension of detour increases, the fractal dimension of pore decreases, the effect of gas slippage increases, but the adsorption effect is still dominant. The apparent permeability of inorganic matter is decreasing in general; The adsorption gas desorption of organic matter makes the effective diameter correction factor increase gradually, the fractal dimension of detour decreases, the fractal dimension of pore increases, the slippage effect and Knudsen diffusion increase in the low pressure pore, and the apparent permeability of organic matter increases. The apparent physical parameters of organic matter and inorganic matter vary with the pressure, and the difference of permeability is large. Therefore, the difference between the apparent permeability of shale matrix and that of organic matter should be distinguished and calculated in order to avoid the error caused by the difference.
【作者单位】：中国石油大学(北京)石油工程教育部重点实验室;中国石油大学(北京)提高采收率研究院;
【基金】：国家自然科学基金项目“裂缝性油气藏流固耦合渗流基础研究”(50004002)
【分类号】：TE312

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