21e: Large-Aperture Fine-Scale Passive Seismic Monitoring for Carbon Storage with DAS

Carbon Capture and Storage is a vital technology to reduce carbon levels in the atmosphere, combat global warming and address climate change. Seismic monitoring is a critical part of a carbon storage project, both to assess the suitability of a site prior to CO2 injection and later to ensure that injected CO2 remains in place and does not leak into other geologic layers, does not trigger earthquakes on nearby faults, and does not reach the surface. Current seismic monitoring involves labor-intensive mobilization of people and equipment each time a survey is conducted. For this reason, surveys are acquired infrequently, and may miss rapid, unexpected changes in CO2 reservoirs. For safety and efficiency, it is crucial to acquire data continuously to quickly identify any changes in the reservoir that might pose a safety or operational risk and alert the operators. Seismic monitoring is also commonly conducted with sensors placed solely on the Earth’s surface. Given the distance of sensors from the CO2 plume that may lie thousands of feet deep, monitoring may also miss weak events that provide an early indicator of problems. We will develop a real-time passive seismic monitoring system by deploying specially engineered fiber-optic cables on the surface, in shallow boreholes and in injection wells. This creates a 3D sensing array with optimal sensing geometry and sensitivity, able to detect weak events. Cables can be permanently installed for use in repeat surveys and are very cost effective compared to traditional sensors. Fiber optic cables provide measurements at every point along the fiber, giving many times more channels of data than traditional sensors, helping to detect and locate weak events. During Phase I, we will design an optimal large-aperture densely spaced sensor layout for a Phase II field trial site. We will model proposed array designs and consider, based on local geologic information, whether the addition of specialized fiber-optic cables – highly-sensitive high-backscatter fiber and multi-component fiber – or multicomponent point sensors is required to achieve the necessary sensitivity to detect small magnitude seismic events (M < 0) and determine their source mechanism. We will adapt our existing microseismic software for large sensor array event detection and real-time automated analysis in the field, as well as alerting operators of any issues through a secure cloud-based system. This project will provide a novel turnkey system for continual monitoring of commercial-scale carbon storage operations by integrating specially designed distributed fiber-optic sensing cables with streamlined onsite analysis, reporting, aggregation in the cloud, and alert mechanisms. This system is designed to be usable for the entire life cycle of the carbon storage operation and will provide continuous monitoring of induced seismicity, as well as changing subsurface conditions. This will minimize unwanted societal or infrastructure impact, non-productive shut-down times and maximize operational performance. The long-term goal is to reduce the cost and complexity of monitoring carbon storage projects, so that carbon capture technology can be scaled up more rapidly, to remove more greenhouse gases from the atmosphere to meet societal goals for addressing climate change.