Three different outcrops are selected in this study, each representing a shallow-marine system with varying heterogeneity provided by siliciclastic–carbonate mixing that may form a small or large stratigraphic trap. The impact of these styles of mixed facies on CO₂ storage is relatively poorly known. This study demonstrates the significance of these systems for safe CO₂ geological storage, as stratigraphic traps are likely to be a significant feature of many future storage sites. The three 3D models are based on: (1) the Grayburg Formation (USA), which displays spatial permeability linked to variations in the mixture of siliciclastic–carbonate sediments; (2) the Lorca Basin outcrop (Spain), which demonstrates the interfingering of clastic and carbonate facies; and (3) the Bridport Sand Formation outcrop (UK), which is an example of a layered reservoir and has thin carbonate-cemented horizons. This study demonstrates that facies interplay and associated sediment heterogeneity have a varying effect on fluid flow, storage capacity and security. In the Grayburg Formation, storage security and capacity are not controlled by heterogeneity alone but are influenced mainly by the permeability of each facies (i.e. permeability contrast), the degree of heterogeneity and the relative permeability characteristic of the system. In the case of the Lorca Basin, heterogeneity through interfingering of the carbonate and clastic facies improved the storage security regardless of their permeability. For the Bridport Sand Formation, the existence of extended sheets of cemented carbonate contributed to storage security but not storage capacity, which depends on the continuity of the sheets. These mixed systems especially minimize the large buoyancy forces that act on the top seal and reduce the reliance of the storage security on the overlying cap rock. They also increase the contact area between the injected CO₂ and brine, thereby promoting the CO₂ dissolution processes. Overall, reservoir systems with mixed carbonate–siliciclastic facies contribute to improving the safe and effective storage of CO₂.

Thematic collection: This article is part of the Geoscience for CO₂ storage collection available at: https://www.lyellcollection.org/cc/geoscience-for-co2-storage

本研究选择了三个不同的露头，每个都代表一个浅海系统，具有不同的非均质性，由硅质碎屑 - 碳酸盐混合提供，可能形成或大或小的地层圈闭。这些混合相类型对 CO ₂储存的影响相对鲜为人知。这项研究证明了这些系统对于安全 CO ₂的重要性地质储存，因为地层圈闭很可能成为许多未来储存地点的重要特征。这三个 3D 模型基于：(1) Grayburg 组（美国），其显示与硅碎屑 - 碳酸盐沉积物混合物的变化相关的空间渗透率；(2) Lorca 盆地露头（西班牙），表明碎屑相和碳酸盐岩相交汇；(3) Bridport Sand Formation 露头（英国），这是层状储层的一个例子，具有薄的碳酸盐胶结层。这项研究表明，相相互作用和相关的沉积物异质性对流体流动、储存能力和安全性有不同的影响。在 Grayburg 组中，存储安全性和容量不仅受非均质性控制，而主要受各相渗透率的影响（即 渗透率对比）、非均质性程度和系统的相对渗透率特征。在 Lorca 盆地的情况下，通过碳酸盐岩和碎屑岩相的相互作用，无论其渗透性如何，都提高了存储安全性。对于 Bridport 砂层，胶结碳酸盐岩扩展片的存在有助于储存安全，但不利于储存容量，这取决于片的连续性。这些混合系统尤其最大限度地减少了作用在顶部密封件上的大浮力，并减少了储存安全对上覆盖岩的依赖。它们还增加了注入的 CO 之间的接触面积 通过碳酸盐岩和碎屑岩相的相互作用，无论其渗透性如何，均质性提高了储存安全性。对于 Bridport 砂层，胶结碳酸盐岩扩展片的存在有助于储存安全，但不利于储存容量，这取决于片的连续性。这些混合系统尤其最大限度地减少了作用在顶部密封件上的大浮力，并减少了储存安全对上覆盖岩的依赖。它们还增加了注入的 CO 之间的接触面积 通过碳酸盐岩和碎屑岩相的相互作用，无论其渗透性如何，均质性提高了储存安全性。对于 Bridport 砂层，胶结碳酸盐岩扩展片的存在有助于储存安全，但不利于储存容量，这取决于片的连续性。这些混合系统尤其最大限度地减少了作用在顶部密封件上的大浮力，并减少了储存安全对上覆盖岩的依赖。它们还增加了注入的 CO 之间的接触面积 这取决于纸张的连续性。这些混合系统尤其最大限度地减少了作用在顶部密封件上的大浮力，并减少了储存安全对上覆盖岩的依赖。它们还增加了注入的 CO 之间的接触面积 这取决于纸张的连续性。这些混合系统尤其最大限度地减少了作用在顶部密封件上的大浮力，并减少了储存安全对上覆盖岩的依赖。它们还增加了注入的 CO 之间的接触面积₂和盐水，从而促进 CO ₂溶解过程。总体而言，具有混合碳酸盐-硅质碎屑相的储层系统有助于提高 CO ₂的安全有效封存。

专题收藏：本文是 CO ₂储存地球科学收藏的一部分，可从以下网址获取：https://www.lyellcollection.org/cc/geoscience-for-co2-storage