Still or sparkling: Microseismic monitoring of CO2 injection at In Salah

捕获燃煤发电厂排放的二氧化碳并将其储存在深层地下储油层中是可能的，例如成熟的油层。这种碳捕获和储存(CCS)技术显示了在满足世界能源需求的同时减少人类温室气体排放的潜力。此外，如果CCS允许开发下一代清洁燃煤电厂，估计将为英国经济带来65亿GB的价值，创造10万个就业机会。然而，为了保证储存的安全，必须建立监测方法，能够跟踪二氧化碳在地下的移动，并成像二氧化碳注入对地下岩石的影响。当向储层注入二氧化碳时，压力变化会导致重新激活的裂缝网络发射地震能量。通过检测这些微震辐射，就有可能确定地下对二氧化碳注入的反应。我们建议在阿尔及利亚的In Salah试点CCS项目中研究由地质力学变形引起的微震事件。该项目为研究利用微地震监测对二氧化碳注入引起的地质力学变形进行成像提供了一个极好的机会。通过定位微震发射的震中，将有可能识别发生变形的区域，如果事件聚集到离散的表面，则可以识别地下活跃的变形断层。活动断裂的识别对于了解油藏上方的地质力学变形是至关重要的。因萨拉赫的地质力学变形是从水库上方地表的抬升推断出来的。根据In Salah的地表变形数据建立的地质力学模型已被用来估计水库中发生的变形。微地震观测将提供更直观的储集层变形图像。我们将使用地震地点来校准和基准地质力学模型，区分预测微震活动的模型和不能预测微震活动的模型。通过以这种方式校准我们的地质力学模型，我们可以确定那些可能给出良好预测的模型，从而评估由于变形而造成的泄漏风险。将地球物理数据、大地测量数据(地表变形)和地质信息联系起来以建立地质力学模型的能力对于确定变形引起的泄漏风险至关重要，并构成该项目的一个关键目标。到目前为止，CCS的一个地点(韦伯恩)已经部署了微地震监测。布里斯托尔地震学小组能够使用微地震数据极大地提高我们对储集层中正在进行的地质力学过程的了解。欧盟打算在2015年前启动至少12个CCS站点，其中许多可能部署微震监测。因此，这个项目非常及时，因为在开始大规模的CCS作业之前，有必要评估这种(和其他)监测技术的可行性。我们在韦伯恩微震活动方面的经验意味着布里斯托尔大学是进行这项研究的理想地点，因为我们将能够利用之前获得的知识来比较和对比两个不同CCS站点的微震活动，从而得出关于部署微震技术来监测CCS的更一般的结论。

It is possible to capture emissions of CO2 from coal fired power plants and storing them in deep subsurface reservoirs such as mature oil reservoirs. This Carbon Capture and Storage (CCS) technology has demonstrated the potential to reduce mankind's greenhouse gas emissions while meeting the world's energy needs. Furthermore, if CCS allows the development of the next generation of clean coal power plants, it will be worth an estimated £6.5billion to the U.K. economy, creating 100 000 jobs. However, to guarantee security of storage, monitoring methods must be in place that can track the movements of CO2 through the subsurface, and image the effects of CO2 injection on the subsurface rocks. When CO2 is injected into reservoirs, the pressure changes can lead to the emission of seismic energy from reactivated fracture networks. By detecting these microseismic emissions, it is possible to determine how the subsurface is responding to CO2 injection. We propose a study of microseismic events induced by geomechanical deformation at the In Salah pilot CCS project, Algeria. This project presents an excellent opportunity to study the utility of using microseismic monitoring to image geomechanical deformation induced by CO2 injection. By locating the hypocenters of microseismic emissions, it will be possible to identify regions where deformation is occurring, and, if events cluster onto discrete surfaces, to identify actively deforming faults in the subsurface. The identification of active faults is crucial for understanding the geomechanical deformation above the reservoir. Geomechanical deformation at In Salah is inferred from the uplift of the ground surface above the reservoir. Geomechanical models based on surface deformation data at In Salah have been used to estimate the deformation occurring in the reservoir. Microseismic observations will provide a much more direct image of deformation of the reservoir. We will use event locations to calibrate and benchmark geomechanical models, distinguishing between models that do a good job of predicting microseismicity and those that do not. By calibrating our geomechanical models in this manner we can determine those that are likely to give good predictions going forward, and thereby assess the risks of leakage due to deformation. The ability to link geophysical data, geodetic data (surface deformation), and geological information to build geomechanical models is crucial for determining the risks of leakage due to deformation, and forms a key goal of this project. Thus far one CCS site (Weyburn) has deployed microseismic monitoring. The Bristol Seismology Group were able to use the microseismic data to greatly improve our understanding of the ongoing geomechanical processes in the reservoir. The EU intends to initiate at least 12 CCS sites by 2015, many of which may deploy microseismic monitoring. This project is therefore very timely in that it is necessary to assess the feasibility of this (and other) monitoring techniques before large-scale CCS operations begin. Our experience with microseismicity at Weyburn means that Bristol University is ideally placed to conduct this research, as we will be able to draw on previously acquired knowledge to compare and contrast microseismicity at the two different CCS sites, and thereby come to more general conclusions regarding the deployment of microseismic techniques to monitor CCS.