砂泥岩裂隙岩体埋深和岩性对渗透性影响分析
Variation of permeability with depth and lithology in a formation of fractured sandstone-mudstone media
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摘要: 采用表征岩体渗透性的单位吸水量ω为参数,有效地分析了砂泥岩裂隙岩体中相对埋深和岩性对渗透性空间分布规律的影响.研究区内,在不同深度单位吸水量的最大值和最小值相差3-4个数量级,渗透性表现出显著的随机特征.通过将压水试验数据离散化并在不同深度上取logω的平均值,凸现了渗透性的结构特征.ω均值在一定范围内随相对深度表现出负指数分布规律;剔除logω的线性趋势项后,logω残差表现出与地层内部岩性相对应的规律.此外,研究还发现,渗透性参数随相对深度呈负指数分布规律是由含裂隙的砂岩介质引起的.这些规律为裂隙岩体的渗流计算和模拟奠定了基础.文章所提出的对压水试验数据离散化并在不同深度取均值以找出渗透性和深度关系,以及去除线性趋势项研究渗透性和岩性之间关系等方法具有广泛的应用价值.Abstract: In this paper,the spatial variation of permeability with depth in a formation of the fractured sandstone mudstone media is analyzed The permeability value is represented by unit absorption ω obtained from the packer permeability test.The variability of permeability is so significant that the value of ω spans 3 to 4 orders of magnitude at different depths By taking mean value of log ω at different depths,the pattern of permeability versus relative depth is easy to discover We found that the variation of permeability with relative depth obey the exponent ial law; After subtract ing the linear trend of log ω with depth,the residual of log ω can be well correlated with the distribution of mudstones In addition,the linear trend of log ω with depth is caused by the fractured sandstone.The spat ial structure of permeability in the study area is clearly and quantitatively characterized by the methods proposed in this paper,which can be utilized for researches on similar studies areas.