Mission Innovation task force reports on enabling Gigatonne-scale CO2 storage
Phil Ringrose and Curt Oldenburg
Journal name: First Break
Issue: Vol 36, No 7, July 2018 pp. 67 - 72
Special topic: Unconventionals & Carbon Capture and Storage
Info: Article, PDF ( 1.12Mb )
Price: € 30
A group of scientists from six countries (France, Netherlands, Norway, Saudi Arabia, UK and the US) met over three days in September 2017 in Houston, Texas, to brainstorm and debate the most promising research directions needed to make breakthroughs in the areas of injectivity and capacity that currently pose challenges to carrying out large-scale (gigatonnes CO2 per year) geologic carbon sequestration. Several CO2 storage projects around the world have demonstrated the feasibility of injecting and storing CO2 at the mega-tonne per year scale. These include the long-running Sleipner project (Norway) which started in 1996 and which has stored ~17 Mt of CO2 to date, and the Illinois Basin Decatur Project (USA) which has stored approximately 1 Mt of CO2. New projects have started over the last few years, including the QUEST project in Canada, the Gorgon project in Australia, and the Industrial Carbon Capture and Storage (ICCS) project at Decatur, Illinois, which will inject 1 Mt CO2/yr. These projects along with a wealth of injection experience from the oil and gas industry over decades, supported by an extensive literature of theory and modelling analyses, provide confidence in the subsurface storage concept intrinsic to CCUS. The challenge ahead is to ramp up CCUS technology to be able to safely store CO2 at the gigatonne (Gt) per year scale to meet global CO2 emissions reductions targets. Although sufficient capacity exists in theory to store CO2 at the Gt/year scale in the continental and offshore sedimentary basins of North America, Europe, and worldwide, there are many technical challenges that need to be addressed. First, more accurate estimates of storage capacity are needed over large areas (~103–104 km2) that have been targeted for storage, with associated challenges for site characterization, monitoring and storage verification. Second, whereas the few current projects are isolated in the given storage reservoirs and often within entire sedimentary basins, injections at the Gt/year scale must involve multiple large-scale projects potentially within tens of kilometres of one another and accessing similar stratigraphic intervals and probably similar reservoir units. To achieve this degree of scale-up, a better understanding of the permissible pressure increase in these large regions is needed. Pressurization from injection projects is known to extend from 10s to 100s of km from the injection wells, and interference among neighbouring projects is inevitable. Thus, there is the need for detailed understanding of the tolerance for pressure rise and potentially the need for pressure management. Furthermore, large-scale projects will require smart methods for controlling and optimizing CO2 injection, which will involve developing better understanding of the links between small (e.g., sub-pore and pore scale) and large-scale physical processes in the reservoir. The key technical issues, questions, and areas in need of better understanding include: • CO2 migration and trapping processes; • Understanding when and how caprocks fail; • Physics- and chemistry-based understanding of CO2 flow at all scales in the reservoir and storage complex; • Impact of flow processes on storage at multiple scales within heterogeneous rock media. In addition to laboratory and field studies, there are many challenges that will require developments in the theory, modelling, and simulation of CO2 storage processes. The research challenges identified by the group on Storage Injectivity and Capacity aim to exploit recent advances in the understanding of flow processes and in the use of high-performance computing, using large data sets to improve the forecasting of CO2 migration and trapping processes, the nature of pressurization and dynamic pressure limits, reservoir fracturing and dynamic geomechanical behaviour of rock units. After brainstorming the issues, the Expert Panel developed three ‘Principle Research Directions’ (PRDs) considered to be essential to the future ramp-up of CCUS to the Gt scale: • Advancing multi-physics and multi-scale fluid flow to achieve Gt/yr capacity; • Dynamic pressure limits for Gigatonne-scale CO2 injection; • Optimal injection of CO2 by control of the near-well environment. These global research propositions are outlined in the report (Mission Innovation, 2017). Here we summarize the research ambitions involved. The expert group focused primarily on storage in saline aquifers and depleted oil and gas fields, as they are expected to have the largest potential for Gt-scale storage, although the concepts will be relevant to all storage options (including CO2EOR). A key part of the learning process for globally significant scale-up of CO2 storage has been the insights gained from early mover projects. This experience has been summarized in various monographs [e.g., Chadwick et al., 2008; Hitchon, 2012] and review papers [e.g., Jenkins et al., 2015; Pawar et al., 2015]. Some key achievements in the development of CO2 storage include: • How seismic monitoring can be used to monitor saturation and pressure changes associated with the growth of the CO2 plume; • How downhole pressure monitoring can be used to understand the pressure distribution and evolution at storage sites; • Understanding the rock mechanical response to injection; • Insights into the complexity of storage reservoirs and the impact of heterogeneity on CO2 flow paths; • Development of optimal monitoring and risk management procedures. These early-mover CO2 storage projects and the associated research studies demonstrate both the technical viability of CO2 storage and its challenges, while also pointing to the key technologies involved in project execution. This gives us an excellent basis for the research directions identified in this report, focused on the theme of significant scale-up via improved insights from multi-physics analysis of CO2 storage (Figure 1).