Sensor systems to monitor injection and long-term subsurface storage of carbon dioxide

碳捕获与封存是一项新兴技术，将二氧化碳在排放源处捕获或分离，液化，然后注入深部地质储层进行长期储存。这一过程有可能在减缓大气中人为二氧化碳水平上升方面发挥核心作用。然而，广泛采用将需要准确可靠的长期监测，以保证安全存储。最先进的监测方法无法提供这种保证。地球物理方法无法探测到深层地层中的溶解和矿化二氧化碳，而地球化学方法基于井下采样，这排除了高采样率，并且由于样品上升到地面时发生的状态变化而受到干扰。因此，迫切需要一种方法，从注入二氧化碳的深层地层和二氧化碳可能迁移的邻近地层中就地收集高频二氧化碳浓度数据。拟议的研究计划通过研究和开发光纤传感器来监测储层内部和附近的二氧化碳浓度，以满足这一需求。光纤传感器系统具有空间和时间分辨率高、长距离传输时信号损耗低、抗电磁干扰和抗短路等特点，非常适合井下环境。我们将研究和开发的传感器将使用光纤设备监测井下流体的二氧化碳浓度，这些设备包括：长周期光栅、光子晶体光纤马赫-曾德干涉仪和光纤尖端折射仪。这些传感器将收集折射率数据，用于确定井下多流体环境中的二氧化碳浓度。这些传感器还将用于确定相和种类（例如盐水、液态碳氢化合物、气态甲烷、液态二氧化碳），这将能够监测深海注入点可能存在的二氧化碳和甲烷泄漏，这些地方可能存在二氧化碳和甲烷，并且很难区分。拟议的研究计划包括在实验室开发和测试传感器，并在陆基和深海地点进行现场部署。拟议的研究计划还将应用于监测二氧化碳储存地点以外的领域。特别是，对二氧化碳浓度的更高灵敏度将使这些传感器能够用于测量浅层地下二氧化碳的自然水平和通量，这对于评估人类活动对大气中二氧化碳浓度的影响至关重要。增强的RI灵敏度还将使广泛的非二氧化碳应用成为可能，其中RI是或有可能成为关键指示参数。*************

Carbon capture and sequestration is an emerging technology in which CO2 is captured or separated at the emission source, liquefied and then injected into deep geologic reservoirs for long term storage. This process has the potential to play a central role in mitigating rising levels of anthropogenic CO2 in the atmosphere. However, widespread adoption will require accurate and reliable long term monitoring to provide assurance of secure storage. State-of-the-art monitoring methods cannot provide this assurance.  Geophysical methods are unable to detect dissolved and mineralized CO2 in deep formations while geochemical methods are based on down hole sampling which precludes high sample rates and is confounded by changes of state that occur as the sample is raised to the surface. There is, therefore, an urgent need for methods to gather high frequency CO2 concentration data in situ from the deep formations where CO2 is injected and in adjacent formations into which CO2 may migrate. The proposed Research Program addresses this need through research and development of fiber optic sensors to monitor concentrations of CO2 in and adjacent to the storage formation. Fiber optic sensor systems are well-suited to the downhole environment due to their high spatial and temporal resolution, low signal loss over long transmission distances and immunity to electromagnetic interference and short circuits.***The sensors that we will research and develop will monitor CO2 concentrations of downhole fluids in situ using fiber optic devices that will include: Long Period Gratings, Photonic Crystal Fiber Mach-Zehnder Interferometers and Fiber Tip Refractometers. These sensors will gather refractive index data that will be used to determine CO2 concentrations in the multi-fluid downhole environment. These sensors will also be used to determine phase and species (e.g. brine, liquid hydrocarbon, gaseous methane, liquid CO2) which will enable monitoring of possible leakage of CO2 at deep ocean injection sites where CO2 and methane can both be present and can be challenging to distinguish. The proposed Research Program includes development and testing of sensors in the laboratory and field deployments at both land-based and deep ocean sites. The proposed Research Program will also have application beyond monitoring of CO2 storage sites. In particular, higher sensitivity to CO2 concentrations will enable these sensors to be used for measurements of natural levels and fluxes of CO2 in the shallow subsurface which are essential to assessing the impacts of human activity on CO2 concentrations in the atmosphere. Enhanced RI sensitivity will also enable a wide range of non-CO2 applications in which RI is or has potential to be a key indicating parameter.*************