Book Review: How to Store C02 Underground

Philip Ringrose’s new book, ‘How to Store CO2 Underground: Insights from early-mover CCS Projects’ is a clear, well-illustrated summary of the geological and engineering aspects of CO2 sequestration. Ringrose, who shares his affiliations between NNTU, Equinor and the University of Edinburgh, acknowledges a bias towards Norwegian and European projects and Equinor’s CCS operations. However as these, especially Equinor’s, are copiously studied and published, this is hardly a disadvantage. Ringrose’s ‘essential message’ is that the engineered geological storage of CO2 is a relatively straightforward and established technology which will be urgently needed in the coming decades.

How to Store* begins with a short history of fossil fuels and C02 in the light of recent targets for global warming. The CO2 story is quite an old one. Fourier, the geophysicists friend, first mooted the warming potential of the earth’s atmosphere. In 1896, Arrhenius pinned most of the warming on CO2. In 1958, atmospheric data collection CO2 at the Mauna Loa observatory on Hawaii began. Ice core data pushed the curve back to 1815. CO2 has risen inexorably, from 280 to over 400 ppm currently. A telling graph shows summarizes the ever-rising CO2 levels along with the hypothesized trajectories that could result from achievable (but as yet unrealized) reductions in output. The maximalist hypothesis, a 50% reduction by 2050, still falls considerably short of the 1.5° target of 2018 IPCC report.

The case for CCS is thus clear, particularly for those working in the oil and gas industry. Today, fossil fuel makes up some 80% of the world’s energy supply and transport, manufacturing and agriculture are highly dependent on fossil energy. A transition period is needed during which CCS (and other measures) are urgently needed.

Ringrose observes that the ‘likely level of growth’ of these energy options is widely debated. CCS provides a mechanism for decarbonising both existing power supply and reducing emissions from industry (e.g. cement and steel manufacture). CCS allows the energy transition to be achieved faster and cheaper than by using only renewable energy sources. In conjunction with bio-energy combustion CCS enables ‘negative net-CO2 emissions’. The counter arguments are that CCS is too expensive and that it encourages fossil fuel usage to continue longer than necessary. Ringrose does not see these as either-or options, rather, it is just a question of how much CCS will actually be used during the energy transition.

How to Store runs through the three pillars of CCS, capture, transport and storage. Each process may seem quite simple, but the quixotic behavior of CO2 (phase transformations, compressibility and thermodynamics, and corrosion) make for pitfalls in each stage of the process.

Storage can be achieved in saline aquifers (the greatest potential), in depleted oil and gas reservoirs (with the merit that they are well understood and the infrastructure is in place). Storage can also be achieved as a part of oil enhanced recovery (EOR) projects, as per carbon capture, utilization and storage (CCUS).

To store significant volumes of CO2, the gas must be compressed. Thus, a depth of over 800 m is necessary. Storage also requires a seal to prevent CO2 from migrating upwards and out of the formation. The parallels with oil and gas exploration are clear. At depths of over a kilometer, ‘we know that natural gas has been trapped beneath geological seals for millions of years, and so the potential for long-term trapping of CO2 at these depths is also clearly possible’.

The essential questions for a project; how much can we inject? And can we store it safely and cost-effectively? Such considerations translate into geology, well design, reservoir modelling and other issues familiar to the upstream. The activity is regulated, in the EU by the EU CCS Directive (EC 2009; annex 1) which mandates data collection and modelling and monitoring to detect any leakage. In anticipation of future projects, the EU GeoCapacity Project has evaluated and mapped the potential for CCS, likewise, the North American Carbon Storage Atlas covers USA, Canada and Mexico. These government-sponsored, projects demonstrate that there is plenty of capacity available. Although things are more nuanced when considering the economics, true storage capacity and matching CO2 sources with the sinks.

Poster child for Norwegian CCS (and for How to Store) is Sleipner, which has been in operation since 1996. Sleipner has been extensively modelled and monitored with 20 years of time-lapse seismic imaging of the CO2 plume. In Salah (Algeria) and Snøhvit (Norway) are used to illustrate CO2 storage flow dynamics, again with many parallels with oil and gas such as static rock property models, two phase fluid flow and dynamic flow simulations.

The niceties of transporting CO2, which may be held just above the boiling point for smaller shipping solutions or chilled to around 45 °C, recall the technology of the LNG business.

How to Store concludes with a chapter on ‘what’s next’ for CCS. Today there are 19 large-scale CCS facilities in operation with an installed capture capacity of 36 Mtpa, most acting in the CCUS space for EOR. The IEA states that ‘two decades of CCS has led to a growing recognition by climate experts of the value and potential of the technology’. Unfortunately, such recognition has not been matched with increased support. CCS has been ‘hampered by fluctuating policy frameworks and lack of financial support’. CCS is essential to meeting the greenhouse gas reduction goals, but it is progressing much too slowly. The main problem is ‘socio-economic’. The cost is perceived to be too high and the benefits are perceived to be too low. Such perceptions need to change, ‘CO2 storage is a lot safer and better than putting the same CO2 into the atmosphere’. A single CO2 injection well can make for very significant emissions reduction. Increases in the ‘carbon price’ will make CCS increasingly attractive, although sequestration from the iron, steel and cement industrial sectors are only likely to proceed with carbon prices of over $100/tonne.

In this review we have cherry picked the narrative. In fact, How to Store provides a wealth of accessible technical information on CCS from a geological and engineering standpoint. Mathematical equations are presented for reference and the book is well illustrated with 4D seismics, well schematics, cross sections and more. For researchers, How to Store provides some 12 pages of references! Coverage is not so strong in the fields of CCUS/EOR, perhaps reflecting its EU bias. Also, the economics and social acceptability of CCS are only touched upon. There is no mention, for instance of ‘Germany’s No to CCS. As Ringrose observes, successful projects to date all occur in national jurisdictions ‘where some kind of legal and financial framework is in place’.

* How to Store CO2 Underground: Insights from early-mover CCS Projects. 140 pages. Springer Briefs in Earth Sciences. ISBN 978-3-030-33112-2.

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