Abstract

During the past decades, greenhouse gas mitigation techniques such as Carbon dioxide Capturing, Utilization, and Sequestration gained more attention due to the environmental concerns associated with the adverse impacts of global warming. Besides the feasibility of capturing and long-time storage of the CO₂, it is of utmost importance to ensure longevity and safety of long-term CO₂ storage. To evaluate the effects of CO₂ injection into a deep saline reservoir, CO₂-enriched brine was injected into the Triassic Peco sandstone in controlled-laboratory experiments. The injection was performed through a core-flooding experiment in which CO₂-enriched brine was injected under a very slow rate, to capture the short/long-term chemical reactions between the rock minerals and CO₂-enriched brine. The injection experiment was performed under different confining stresses and pore-pressures to mimic reservoir conditions at different depths. The creep, ultrasonic wave (i.e., P- and S-Wave) velocity measurements, and multi-stage failure tests were conducted on intact, and CO₂-enriched brine injected Peco Sandstone specimens to capture potential changes in time-dependent deformation, strength properties, and P- and S-Wave velocities. The results indicated a significant increase in the creep response. At the same time, strength properties and ultrasonic wave velocities exhibited significant reductions, due to the dissolution of grain boundaries and cementing minerals, which was caused by the injection of CO₂-enriched brine. Results of this study indicate that the potential increase in time-dependent deformation (i.e., creep rate) should be considered at the reservoir scale since the accelerated creep behavior can potentially lead to reservoir compaction, which consequently endangers wellbore stability and caprock integrity. In addition, the significant reduction in cohesion and friction angle can likely increase the slip tendency of the reservoir rock under certain injection scenarios, which consequently increases the possibility of fault reactivation.

中文翻译：

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注入富含CO 2的盐水后砂岩的破坏特性，蠕变响应和超声速度的变化

摘要

在过去的几十年中，由于与全球变暖的不利影响相关的环境问题，诸如二氧化碳捕获，利用和封存之类的温室气体减排技术受到了越来越多的关注。除了捕获和长期储存CO ₂的可行性外，确保长期储存CO _2的寿命和安全性也至关重要。为了评估向深盐储层中注入CO ₂的效果，在控制实验室实验中，将富含CO _2的盐水注入三叠纪Peco砂岩中。通过岩心驱油实验进行注入，其中CO ₂以非常缓慢的速率注入富含盐水的盐水，以捕获岩石矿物与富含CO _2的盐水之间的短期/长期化学反应。在不同的围压和孔隙压力下进行注入实验，以模拟不同深度的油藏条件。蠕变，超声波（即P波和S波）速度测量以及多阶段破坏测试均在完整无损的CO _{2上进行。}注入盐水的Peco砂岩标本可以捕获随时间变化的形变，强度特性以及P波和S波速度的潜在变化。结果表明蠕变响应显着增加。同时，由于注入CO ₂引起的晶界和胶结矿物的溶解，强度性能和超声波速度显着降低。-浓缩盐水。这项研究的结果表明，在储层范围内应考虑随时间变化的潜在变形（即蠕变速率）的增加，因为加速的蠕变行为可能导致储层压实，从而危及井筒稳定性和盖层完整性。另外，内聚力和摩擦角的显着减小可能会增加某些注入情况下储层岩石的滑动趋势，从而增加断层再激活的可能性。