(289h) Novel Carbon Storage Monitoring Methods

We present a high-level overview of past and ongoing research efforts led by the Energy & Environmental Research Center (EERC) at the University of North Dakota to demonstrate novel and sustainable carbon storage-monitoring methods at multiple commercial-scale (i.e., >1 million tonnes of carbon dioxide sequestered annually) carbon capture and storage (CCS) sites. Research with our project partners, which has received support from the U.S. Department of Energy (DOE) and Plains CO₂ Reduction (PCOR) Partnership, is aligned with DOE’s goal to advance monitoring technology for carbon dioxide (CO₂) plume tracking and leakage (assurance) monitoring as well as the mission of the PCOR Partnership, a government–industry consortium with over 200 members, to accelerate deployment of commercial-scale CCS technologies.

The EERC has conducted field testing associated with its scalable, automated, sparse seismic array (SASSA) 2.0 technology at a permitted CCS site supported by the PCOR Partnership. A sparse surface array of seismic nodes was deployed around the project site to collect seismic data from midpoints set at multiple azimuths and distances around the injection well for tracking the injected CO₂ plume within the target zone (i.e., storage reservoir) through time-lapse comparison of data acquired between the baseline (preinjection) and the first year and a half of operations. The seismic data were acquired with a set of static seismic sources that were operated remotely after installation. EERC field personnel retrieved and redeployed the seismic nodes about once every 6 weeks to obtain the raw field data for processing. SASSA 2.0 benefitted the local community by providing a low-impact, semiautonomous solution to conducting seismic survey work. Initial processing of the results indicated satisfactory signal-to-noise within the storage reservoir.

The EERC recently completed baseline research activities at a permitted CCS site with DOE support. The overall goal of the project is to demonstrate the commercial readiness of several novel carbon storage-monitoring technologies for the benefit of future CCS projects. Survey planning benefitted from drone surveillance work conducted prior to survey acquisition, which generated a digital elevation model that the planning team used in the geophysical survey designs.

Potential fields methods, such as electromagnetic (EM) surveys, are underutilized in CCS monitoring. A project objective is to use EM methods to quantify saturation changes through electrical resistivity measurements of the near-surface and at-reservoir depths. The near-surface measurements of electrical resistivity can be used to corroborate with nuclear magnetic resonance-logging data planned to be collected from a group of shallow groundwater wells within the area surveyed. This method will provide a novel approach to monitoring the near-surface environment for leakage (assurance monitoring) at a CCS site. To date, the baseline near-surface and at-reservoir EM surveys have been acquired, and initial results indicate satisfactory signal-to-noise.

The EERC also deployed three-component (3C) seismic sensors in strategic surface locations as part of the baseline activities associated with the research overlay supported by DOE. The purpose of the 3C sensors was to measure ambient noise at the site to generate seismic images of the subsurface from the passive (noise) seismic data collected. The method involves estimating the orientation of maximum horizontal compressive stress (SHmax); therefore, measurements of SHmax from core available within the project area were used, and a set of mechanical earth models were created as part of this research. This method will demonstrate a very low-impact method for CO₂ plume monitoring, as no intrusive seismic sourcing is required.

One of the objectives for improving the economics of future seismic surveys is to demonstrate the ability to image a CO₂ plume from repeat 2D seismic lines sourced with conventional seismic sources with varying degrees of decimation. Low-impact mobile seismic sources were also tested at high-density spacing along those 2D seismic lines for testing viability of imaging to the target storage depths. These methods will improve the sustainability of future carbon storage monitoring by reducing impact and cost.

In a similar effort at another site, the EERC is planning to collect a large (>200-square-mile) 3D seismic survey associated with a DOE-supported CCS project. This 3D survey design will implement compressive sensing concepts and serve as a baseline for future carbon storage monitoring. The objective of this task will be to convert the conventional survey design supplied by the selected seismic acquisition contractor into a compressive sensing design that produces superior data density for the same in-field effort and, therefore, reduces costs for future repeat monitor surveys.

As an alternative to acquiring large-scale 3D seismic surveys for CCS projects, the EERC has been involved in past underground injection control Class VI projects where the design of a grid of 2D seismic lines was selected to track the migration of the injected CO₂ plume. Design patterns have varied based on the site-specific needs of the CCS project. In cases where active mining operations are a concern for land use and access to roads, a sparse 2D grid along roads can be used to limit impact to site operations. Another approach involved acquiring 2D seismic lines in a radial pattern around CO₂ injection to create a pseudo-3D image of the injected CO₂ plume.

We presented a high-level overview of many novel and sustainable carbon storage-monitoring methods that are at various stages of planning or demonstration to accelerate the deployment of CCS technologies at future CCS sites across the United States. Our work impacts the general CCS industry by providing novel and more sustainable methods for tracking CO₂ plume migration and performing assurance monitoring. Our work primarily benefits three parties: 1) CCS community members through knowledge sharing of lessons learned; 2) CCS operators through commercialization of additional methods, including improvements on workflows and simplification of fieldwork; and 3) stakeholders of CCS projects through implementation of low-impact and more autonomous monitoring solutions.