Detrital Clay Coats, Clay Minerals, and Pyrite: A Modern Shallow-Core Analogue For Ancient and Deeply Buried Estuarine Sandstones
Detrital Clay Coats, Clay Minerals, and Pyrite: A Modern Shallow-Core Analogue For Ancient and Deeply Buried Estuarine Sandstones
复制标题
碎屑粘土层、粘土矿物和黄铁矿：古代和深埋河口砂岩的现代浅层类似物
DOI：
10.2110/jsr.2018.56
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发表时间：
2018
影响因子：
2
通讯作者：
R. Duller
中科院分区：
文献类型：
--
作者：
J. Griffiths;R. Worden;L. Wooldridge;J. Utley;R. Duller
粘土矿物和自生粘土包衣砂粒在古油藏和深层油藏中的空间展布对储集层质量的提高或降低的作用还知之甚少。据报道，自生粘土涂层起源于碎屑粘土涂层的热驱动重结晶，或通过埋藏成岩过程中前体矿物和早期成岩矿物的自生蚀变而原位生长。为了帮助预测河口砂岩中自生粘土涂层和粘土矿物的空间分布，本研究首次利用英国RavenGlass河口进行了现代模拟研究，该研究整合了岩相、铁硫化物、前驱碎屑粘土涂层和粘土矿物的分布模式。以前所未有的高分辨率确定了23个1米岩心中沉积物的X射线衍射矿物学和碎屑粘土覆盖层的范围。研究结果表明，碎屑粘土矿物的分布模式主要受粘土矿物按粒度进行物理分选的控制。绿泥石在粗粒沉积物(如低幅度沙丘)中最为丰富，而伊利石在细粒次环境(如泥滩)中最为丰富。拉文格拉斯河口高岭石丰度相对均匀，而蒙脱石丰度可以忽略不计。研究表明，碎屑-粘土-涂层和粘土-矿物的分布模式受沉积过程中活跃的过程和原生沉积环境中最上层几毫米处的生物-沉积物相互作用控制。在RavenGlass河口，碎屑粘土层和粘土矿物的分布模式没有受到沉积生物扰动或机械渗透的后期沉积作用的影响。最佳碎屑粘土覆盖度和粘土矿物学特征可能是深埋砂岩储层中保存孔隙度的自生粘土覆盖层的前兆，可能出现在河口内侧和盆地中部的低幅度沙丘上。此外，低幅度沙丘中的生物扰动由于氧化而减少了铁硫化物的生长，这意味着铁仍然可用于形成自生含铁粘土矿物，如绿泥石，这可能会提高深埋砂岩的储集层质量。
The spatial distribution of clay minerals and authigenic-clay-coated sand grains in ancient and deeply buried petroleum reservoirs, which can enhance or degrade reservoir quality, is poorly understood. Authigenic clay coats are reported to originate from the thermally driven recrystallization of detrital clay coats or through in situ growth from the authigenic alteration of precursor and early-diagenetic minerals during burial diagenesis. To help predict the spatial distribution of authigenic clay coats and clay minerals in estuarine sandstones, this study provides the first modern-analogue study, using the Ravenglass Estuary, UK, which integrates the distribution patterns of lithofacies, Fe-sulfide, and precursor detrital-clay-coats and clay-minerals. X-ray-diffraction-determined mineralogy and the extent of detrital clay-coat coverage of sediment in twenty-three one-meter cores was established, at an unprecedented high resolution. The output from this study shows that detrital clay mineral distribution patterns are controlled principally by the physical sorting of clay minerals by grain size. Chlorite is most abundant in coarsergrained sediment (e.g., low-amplitude dunes), whereas illite is most abundant in finer-grained sub-environments (e.g., mud flats). Kaolinite abundance is relatively homogeneous, whereas smectite abundance is negligible in the Ravenglass Estuary. This study has shown that distribution patterns of detrital-clay-coats and clay-minerals are controlled by processes active during deposition and bio-sediment interaction in the top few millimeters in the primary deposition environment. In the Ravenglass Estuary, distribution patterns of detrital-clay-coats and clay-minerals have not been overprinted by the postdepositional processes of sediment bioturbation or mechanical infiltration. Optimum detritalclay-coat coverage and clay mineralogy, which might serve as a precursor to porosity-preserving authigenic clay coats in deeply buried sandstone reservoirs, is likely to occur in low-amplitude dunes in the inner estuary and central basin. Furthermore, bioturbation in low-amplitude dunes has reduced Fe-sulfide growth due to oxidization, meaning that iron remains available for the formation of authigenic Fe-bearing clay minerals, such as chlorite, that can lead to enhanced reservoir quality in deeply buried sandstones.