Abstract The here analyzed Posidonia Shale (PS) samples have relatively high total organic carbon (TOC) contents greater than 2 wt% and are thermally early mature. They, thus, already experienced some generation of petroleum and contain abundant bitumen in the pore space. Solvent core flooding extraction was performed on five clay- and carbonate-rich early-mature Posidonia Shale plugs using dichloromethane (DCM) as permeating fluid under controlled confining pressure in a tri-axial flow cell. Molecular characteristics and differences were observed in original, sequential and residual extracts obtained by core flooding. Furthermore, porosity and permeability changes due to removal of soluble organic matter were recorded. Our results show that core flooding extraction of the clay-rich shales failed due to their low permeability (3.0–5.0 nD), while sequential extraction was successfully performed on the carbonate-rich shales. Acidic compounds were flushed out first, which indicate that these compounds might be preferentially expelled during the early stage of primary migration. Pristane and phytane are preferentially expelled in the whole process of expulsion as compared to n-alkanes. Composition of the other aliphatic (including n-alkanes, hopanes and steranes) and aromatic (including methylnaphthalenes, phenanthrenes, dibenzothiophenes and methyldibenzothiophenes) compounds of the sequential, original and residual extracts do not exhibit much difference. Statistical data indicate that the original and residual extracts have higher similarity and show lower apparent maturity than the sequential extracts indicating that expelled oil might show higher maturity than the related source rock. This observation might be important for interpreting oil/source rock correlations based on geochemical parameters. Porosities of the carbonate-rich shales were slightly smaller than those of the clay-rich rocks, while the permeability is much higher in the carbonate-rich lithologies. It is worth noting that porosity and permeability did not increase during the extraction of soluble organic matter. On the contrary, due to counteracting compaction effects that reduce pore volume extraction lead to an overall porosity and permeability decrease.

中文翻译：

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早熟超致密 Posidonia 页岩岩心驱油层序提取物的分子差异

摘要 这里分析的 Posidonia 页岩 (PS) 样品具有相对较高的总有机碳 (TOC) 含量，大于 2 wt%，并且是热早熟的。因此，它们已经经历了一些石油生成并且在孔隙空间中含有丰富的沥青。使用二氯甲烷 (DCM) 作为渗透流体，在三轴流通池中的受控围压下对五个富含粘土和碳酸盐的早熟 Posidonia 页岩塞进行溶剂岩心驱油萃取。观察了岩心驱替所得的原始、连续和残留提取物的分子特征和差异。此外，还记录了由于去除可溶性有机物而导致的孔隙度和渗透率变化。我们的结果表明，富粘土页岩的岩心驱油由于其渗透率低（3.0-5.0 nD）而失败，而在富碳酸盐页岩上成功地进行了顺序提取。酸性化合物首先被排出，这表明这些化合物可能在初级迁移的早期阶段被优先排出。与正构烷烃相比，在整个排出过程中优先排出丙烷和植烷。其他脂肪族（包括正烷烃、hopanes 和steranes）和芳香族（包括甲基萘、菲、二苯并噻吩和甲基二苯并噻吩）化合物的连续、原始和残留提取物的组成没有表现出太大差异。统计数据表明，原始和残留提取物具有更高的相似性，并显示出比连续提取物更低的表观成熟度，这表明排出的油可能比相关烃源岩显示出更高的成熟度。这一观察结果对于解释基于地球化学参数的石油/烃源岩相关性可能很重要。富碳酸盐页岩的孔隙度略小于富黏土岩石，而富碳酸盐岩性的渗透率要高得多。值得注意的是，在提取可溶性有机物的过程中，孔隙率和渗透率并未增加。相反，由于减少孔隙体积提取的抵消压实效应导致整体孔隙度和渗透率降低。这一观察结果对于解释基于地球化学参数的石油/烃源岩相关性可能很重要。富碳酸盐页岩的孔隙度略小于富黏土岩石，而富碳酸盐岩性的渗透率要高得多。值得注意的是，在提取可溶性有机物的过程中，孔隙率和渗透率并未增加。相反，由于减少孔隙体积提取的抵消压实效应导致整体孔隙度和渗透率降低。这一观察结果对于解释基于地球化学参数的石油/烃源岩相关性可能很重要。富碳酸盐页岩的孔隙度略小于富黏土岩石，而富碳酸盐岩性的渗透率要高得多。值得注意的是，在提取可溶性有机物的过程中，孔隙率和渗透率并未增加。相反，由于减少孔隙体积提取的抵消压实效应导致整体孔隙度和渗透率降低。值得注意的是，在提取可溶性有机物的过程中，孔隙率和渗透率并未增加。相反，由于减少孔隙体积提取的抵消压实效应导致整体孔隙度和渗透率降低。值得注意的是，在提取可溶性有机物的过程中，孔隙率和渗透率并未增加。相反，由于减少孔隙体积提取的抵消压实效应导致整体孔隙度和渗透率降低。