Abstract Chlorite grain coatings in sandstones can inhibit quartz overgrowths and preserve porosity in hot reservoirs, but coatings may also introduce high irreducible water saturation and therefore reduce effective porosity. In order to derive a quantitative model to predict microporosity and effective porosity, five sets of sandstone samples with well-developed chlorite grain coatings were studied. Scanning electron microscopy and X-ray diffraction results on each set indicate various types of chlorite morphology and a broad range of chlorite abundance, though the ratio of the average size to the average thickness of chlorite platelets is constant in all samples. Microporosity, defined in this study as the product of total porosity and irreducible water saturation, is correlated to chlorite by volume content and chemical composition: φmicro = 7.08 × Vchl/(0.39 × Vchl + 2.26) + 0.927 for iron-rich chlorite, and φmicro = 7.08 × Vchl/(1.88 × Vchl + 7.83) + 0.927 for magnesium-rich chlorite, where φmicro is microporosity in porosity units (p.u.) and Vchl is volume percentage (%) of chlorite in the bulk sample. When the total porosity for a sample is known, its effective porosity is the difference between the total porosity and the microporosity.

中文翻译：

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颗粒包覆绿泥石对砂岩有效孔隙度的影响

摘要 砂岩中的绿泥石颗粒涂层可以抑制石英过度生长并保持热储层的孔隙度，但涂层也可能引入高束缚水饱和度，从而降低有效孔隙度。为了推导出一个定量模型来预测微孔隙度和有效孔隙度，对五组具有发育良好的绿泥石颗粒涂层的砂岩样品进行了研究。每组的扫描电子显微镜和 X 射线衍射结果表明了各种类型的亚氯酸盐形态和广泛的亚氯酸盐丰度，尽管所有样品中亚氯酸盐片晶的平均尺寸与平均厚度的比率是恒定的。在本研究中，微孔隙度定义为总孔隙度和束缚水饱和度的乘积，通过体积含量和化学成分与亚氯酸盐相关：φmicro = 7。08 × Vchl/(0.39 × Vchl + 2.26) + 0.927 富铁亚氯酸盐，φmicro = 7.08 × Vchl/(1.88 × Vchl + 7.83) + 0.927 富镁绿泥石，其中 φmicro 是微孔率单位) 和 Vchl 是大块样品中亚氯酸盐的体积百分比 (%)。当样品的总孔隙率已知时，其有效孔隙率是总孔隙率与微孔隙率之差。