Geologic Carbon Sequestration Monitoring

Synopsis

Geologic carbon sequestration has been identified as a potential means of reducing the amount of carbon-dioxide (CO 2) emitted into our atmosphere, thereby reducing one of the major contributors to global warming and climate change. A major difficulty with CO 2 sequestration is monitoring sequestration sites and pipelines for leakage. Initial studies of geologic storage sites indicate that leakage rates must be less that 0.1% to 0.01% per year. Moreover, possible CO 2 sequestration leakage is a significant concern for the public at large, who will almost certainly demand stringent monitoring. Likely causes for CO 2 leakage include leaking injection wells, leakage from poorly sealed abandoned wells, and leakage through geologic faults and fractures. These leakage zones may be on the order of 1 m in size and spread over areas on the order of 100’s of square kilometers. Consequently, CO 2 leak monitoring from sequestration sites and pipelines is a difficult problem of massive proportion and huge importance. The CO 2 leakage monitoring technology proposed here utilizes the natural change in reflectance of vegetation as it responds to CO 2 leakage. Detailed studies have shown that plants exhibit stress as soil oxygen is displaced, thereby suffocating the plant roots. This effect changes the reflectance properties of the plants and is a well-known indicator of exposure to underground gas, including methane and CO 2. Since plants cover a large fraction of potential leakage sites, they provide a massive natural array of sensors for CO 2 leakage. To demonstrate proof-of-concept, researchers at Resonon and Montana State University utilized spectral imaging techniques to monitor controlled CO 2 leaks from an underground pipe designed specifically to test CO 2 monitoring technologies. This facility is known as the Zero Emission Research Technology (ZERT) facility. Our research to date clearly demonstrates that vegetation is stressed by underground leakage of CO 2 and that low-cost spectral imaging can be used to identify this stress.