Hydrocarbon-bearing shale formations might be an attractive geologic reservoir for permanent carbon dioxide (CO₂) storage. Shale formations applicable for storage require previous hydrocarbon production to deplete a reservoir, hydraulic fracturing to provide a highly-permeable stimulated zone, sufficient depths (generally > 800 m or 2600 feet) to maintain CO₂ in a supercritical state, and an overlying seal to prevent CO₂ migration to underground sources of drinking water and into the atmosphere. CO₂ is stored in shale as a free phase within fractures and matrix pores, and as a sorbed phase on organic matter and clay minerals. Recently in our previous work, we presented a screening-level assessment methodology for CO₂ storage in shales using a volumetric approach. The approach deals with reduction of CO₂ storage through estimations of efficiency factors based on petrophysical properties (i.e., bulk volume, porosity, sorption, etc.) and their limitations on fluid transport. Here, we conducted numerical simulations using the FRACGEN/NFFLOW simulator to study the CO₂ injection into a depleted hydro-fractured shale reservoir to estimate storage efficiencies using a range of reservoir parameters and injection scenarios. Specifically, the ranges for two efficiency factors, $E_{\varphi }$ and $E_S$, measure the effectiveness of free and sorbed CO₂ storage. These efficiency factors were estimated to have P₁₀ to P₉₀ probability ranges of 0.15 to 0.36 for $E_{\varphi }$ and 0.11 to 0.24 for $E_S$, reported after 60 years of CO₂ injection.

含烃的页岩地层可能是永久性二氧化碳（CO ₂）储存的有吸引力的地质储层。适用于存储的页岩地层需要先前的碳氢化合物生产来耗尽储层，需要进行水力压裂以提供高渗透性的受热区，足够的深度（通常> 800 m或2600英尺）以将CO ₂维持在超临界状态，并且需要覆盖上层的封闭层。防止CO ₂迁移到地下饮用水源和大气中。CO ₂以裂缝和基质孔隙中的自由相以及有机物和粘土矿物上的吸附相形式存储在页岩中。最近，在我们之前的工作中，我们介绍了一种针对CO ₂的筛查级评估方法使用体积法将其储存在页岩中。该方法通过基于岩石物性（例如，体积，孔隙率，吸附度等）及其对流体传输的局限性来估算效率因子，从而减少了CO _2的存储量。在这里，我们使用FRACGEN / NFFLOW模拟器进行了数值模拟，以研究将CO ₂注入贫化水力压裂页岩油藏中的情况，从而利用一系列油藏参数和注入情景来估算储藏效率。具体来说，两个效率因子的范围是$E_{\varphi }$ 和 $E_{\mathrm{小号}}$，测量自由和吸收的CO ₂储存的有效性。估计这些效率因子的P ₁₀至P ₉₀概率范围为0.15至0.36$E_{\varphi }$ 对于0.11至0.24 $E_{\mathrm{小号}}$，报道了60年的CO ₂注入后。