Geomechanical Assessment of CO2 Storage Reservoir Integrity Post-closure (GASRIP)

将二氧化碳(CO2)注入深层地质构造被全世界公认为唯一现实的缓解技术，可以减少目前的人为二氧化碳排放，以在2050年实现国家目标。然而，碳捕获和封存(CCS)引起了公众对地质水库二氧化碳潜在地表泄漏的担忧，限制了潜在的封存地点的数量。包括英国在内的欧洲国家已经考虑将枯竭的油气田和含盐含水层(例如北海的Sleipner油田)用于二氧化碳储存，而美国的一些项目则专注于注入二氧化碳以提高枯竭或非常规油气藏的石油采收率(EOR)。它们的地质力学完整性会受到注入二氧化碳后的二氧化碳-流体-岩石相互作用的影响，这可以用热、水文、机械和化学耦合现象(THMC)来量化。CO2注入诱发的THMCs会导致地震活动的增强和CO2向地表的泄漏。因此，CCS和EOR-CCS作业的出现引发了更多研究的需要，以在整个二氧化碳储存周期(持续100多年)内保持储层的地质力学完整性。到目前为止，研究人员一直专注于二氧化碳注入过程中储集层物性的诱导变化(从含盐水地层向含二氧化碳地层的转变)及其相关的超压效应。一般认为，CO2注入中断后，储集层压力下降，CO2羽流运移，自然渗吸作用导致含水层补给。然而，注入二氧化碳是一种干燥过程，在饱和卤水地层中会触发复杂的盐析出现象。几项研究的重点是降低孔隙度和渗透率对注入效率和存储容量的风险。一个较少被认识到的事实是，在封闭条件下生长的盐晶体有可能通过施加巨大的压力(卤化作用)来破坏岩石。在停止注入二氧化碳后，含水层的补给导致盐溶和储集层压实。二氧化碳储存环境中盐析出的假设可逆性尚未得到研究。在注入二氧化碳后的天然含水层补给过程中，我们预计哪些现象会影响储集层的完整性？我们能控制他们吗？随着我们迈向低碳世界，能源行业正在发生变化；CCS和EOR-CCS正在成为石油和天然气行业的基本实践，石油和天然气行业是英国经济的关键部门。解决这些问题对于减少英国温室气体排放所需规模的安全CCS作业至关重要，同时也要提高碳氢化合物储藏库(如英国北海油田)的回收率。该项目旨在通过降低CCS风险和提供一种可能的新的提高采收率方法来满足英国工业战略的清洁能源议程。关闭后的二氧化碳储藏库完整性地质力学评估(GASRIP)是一个主要设计用于研究二氧化碳卤水诱导的盐析出/溶解如何影响二氧化碳储藏库的地质力学完整性的项目。通过在实验室观察天然砂岩的弹性、力学和运输性质的变化，GASRIP将评估注入二氧化碳后盐岩硅屑储层的力学性质的变化。通过分析富含碳酸盐的砂岩，GASRIP将确定二氧化碳注入后对化学反应储层的机械和化学影响。这一信息对于以受控方式使用盐沉淀的可能性，以改善致密油层的运输特性和可行的油气生产(提高采收率替代方案)是必要的。通过将结果整合到数值模型中，GASRIP将为关闭后的二氧化碳储藏库的风险评估提供一个有价值的工具。

Injecting carbon dioxide (CO2) into deep geological formations is recognized worldwide as the only realistic mitigation technology that can reduce current anthropogenic CO2 emissions to meet national targets by 2050. However, Carbon Capture and Storage (CCS) have aroused public concerns over potential surface leakage of CO2 from geological reservoirs, limiting the number of potential storage sites. European countries, including the UK, have considered depleted oil and gas fields and saline aquifers for CO2 storage (e.g. Sleipner field, North Sea), while a number of projects in the United States have focused on CO2 injection for enhanced oil recovery (EOR) in depleted or unconventional hydrocarbon reservoirs.Geological reservoirs are complex systems. Their geomechanical integrity can be affected by CO2-fluid-rock interactions following injection of CO2, which can be quantified in terms of Thermal, Hydrological, Mechanical and Chemical coupled phenomena (THMCs). THMCs induced by CO2 injection can lead to detrimental enhanced seismicity and CO2 leakage to the surface. So, the advent of CCS and EOR-CCS operations has triggered the need for more research to preserve the geomechanical integrity of reservoirs during the whole CO2 storage cycle (lasting 100s years). To date, researchers have focused on the induced changes in the physical properties of the reservoir during CO2 injection (transition from brine-bearing to CO2-bearing formations) and associated overpressure effects. It is generally assumed that following the interruption of CO2 injection, the reservoir pressure decreases, the CO2 plume migrates and natural imbibition leads to aquifer recharge. However, CO2 injection is a drying process that triggers complex salt precipitation phenomena in brine saturated formations. Several studies have focused on the risks associated with porosity and permeability reduction with respect to injection efficiency and storage capacity. A less appreciated fact is that salt crystals growing under confinement have the potential to damage the rock by exerting enormous pressures (haloclasty). After ceasing the CO2 injection, the aquifer recharge leads to salt dissolution and reservoir compaction.The hypothesized reversibility of salt precipitation in CO2 storage contexts has yet to be investigated. Which phenomena do we expect to affect reservoir integrity during the natural aquifer recharge post-CO2 injection? Can we control them? The energy industry is transforming as we move to a lower carbon world; CCS and EOR-CCS are becoming essential practices for the oil and gas industry, a vital sector for the UK economy. Addressing these questions is crucial for the safe CCS operation at the scales needed to mitigate greenhouse gas emissions for the UK, and at the same time improving recovery rates from hydrocarbon reservoirs (e.g., UK North Sea fields). This project seeks to address the UK Industrial Strategy's clean energy agenda by reducing CCS risks, and providing a possible new EOR method.Geomechanical Assessment of CO2 Storage Reservoir Integrity Post-closure (GASRIP) is a project primarily designed to study how CO2-brine induced-salt precipitation/dissolution affects geomechanical integrity of CO2 storage reservoirs. By looking at changes in the elastic, mechanical and transport properties of natural sandstones in the laboratory, GASRIP will assess variations in the mechanical properties in saline siliciclastic reservoirs post-CO2 injection. By analysing carbonate-rich sandstones, GASRIP will determine the mechanical and chemical post-CO2 injection effects on chemically reactive reservoirs. This information is needed for the potential use of salt precipitation in a controlled manner to improve the transport properties and the viable production of oil and gas from tight reservoirs (EOR alternative). By integrating the results in a numerical model, GASRIP will offer a valuable tool for risk assessment of CO2 storage reservoirs post-closure.