Why is Basalt Carbon Sequestration beneficial
Pilot tests have demonstrated that basalt reservoirs provide an alternative and permanent carbon capture scenario (e.g., Carbfix project, Planke, et al. in press). When supercritical CO2 is injected into basalts, it soon reacts with Ca, Mg, and Fe-bearing minerals and forms stabile carbonate minerals (Oelkers et al., 2008). Therefore the need for 4D monitoring for the coming decades will likely be minimal. Basalt is a very reactive micro crystalline blend of minerals, and the following are the most common reactions:
The expectation of vast storage volumes in certain macro porous basalt facies is also predicted. Flow Tops reservoirs report as much as 45% porosity and flow interior up to 8% (Ref Colombia River flood basalts). Regional-sized porous systems will probably avoid the expected reservoir pressure build-up expected in more constricted conventional sandstone reservoirs. Therefore, expectations are that basalt storage will avoid some of the scrutiny required of the overburden integrity and injectivity. The water depth to these storage complexes, up to 2000m, is both a challenge and a benefit. Obviously, drilling in deep waters is more costly than in the shallow North Sea. In 2000m water depth and 4° C, CO2 is a liquid and slightly heavier than water. Any spills at the seafloor should then be undramatic. The liquid CO2 should flow down-dip and eventually dissolve with the seawater.
Massive reservoir volumes mapped within the Norwegian Sea
The figure above shows the regional mapping of basalt distribution and basalt thickness based on TGS seismic data. It illustrates the structure of the Top Basalt horizon (overlain by basalt thickness in brown) and the Top Paleocene horizon (in grayscale). The Skoll High, Møre Marginal High, Erlend Volcano, and East Faroe High are potential test sites for permanent carbon sequestration in the offshore basalts. Seismic 3D data coverage is outlined (Planke S. et al, in press).
Current carbon sequestration occurs in volumes of Mt/a into dominantly sedimentary reservoir rocks. We hypothesize that offshore CO2 sequestration into porous basaltic lava flows may allow permanent CO2 storage of several gigatons per year; however, more research and testing will be required to verify this potential.
