Geochemical and solute transport modelling for CO2 storage, what to expect from it?

Abstract

International audienceGeochemistry plays an important role when assessing the impact of CO2 storage. Due to the potential corrosive character of CO2, it might affect the chemical and physical properties of the wells, the reservoir and its surroundings and increase the environmental and financial risk of CO2 storage projects in deep geological structures. An overview of geochemical and solute transport modelling for CO2 storage purposes is given, its data requirements and gaps are highlighted, and its progress over the last 10 years is discussed. Four different application domains are identified: long-term integrity modelling, injectivity modelling, well integrity modelling and experimental modelling and their current state of the art is discussed. One of the major gaps remaining is the lack of basic thermodynamical and kinetic data at relevant temperature and pressure conditions for each of these four application domains. Real challenges are the coupled solute transport and geomechanical modelling, the modelling of impurities in the CO2 stream and pore-scale modelling applications

Qualitative and quantitative changes in detrital reservoir rocks caused by CO<sub>2</sub>–brine–rock interactions during first injection phases (Utrillas sandstones, northern Spain)

“…Therefore, dry CO 2 interaction with the storage rock is a realistic scenario that takes place during the initial injection stages. Some theoretical studies (Gaus et al, 2008(Gaus et al, , 2010 and experimental results (Sterpenich et al, 2009) on dry CO 2 -rock interactions indicate the absence of reactions and consequently negligible textural-mineralogical changes. This is explained by the lack of H 2 O in the system that prevents dissolution/precipitation and any kind of chemical reactions.…”

“…The Utrillas sandstones belong to a 1100 m thick Cretaceous sequence and crop out near Boñar village in the northern León province. This Cretaceous sequence lays André et al (2007) and Gaus et al (2008). Zone 1: zone not affected by CO 2 injection; Zone 2: acidified zone with dissolution and precipitation of minerals.…”

Evaluation of accessible mineral surface areas for improved prediction of mineral reaction rates in porous media

“…Commonly, a reaction rate law is used where the mineral reaction rate is given by (1a)Rm=AmaH+nk(1-Q/Km) (1b)Rm=AmaH+k [fΔGr] where Am is the bulk reactive surface area (m 2 mineral/m 3 porous medium), kis the rate constant, aH+ is the activity of H + , n is the pH dependence of the reaction, Q is the ion activity product, and Km is the equilibrium constant Lasaga, 1994, Steefel et al, 2015a). Rate law parameters are often arbitrarily adjusted so simulated rates match observed dissolution rates, as summarized by the review in Gaus et al (2008).…”

“…This range of approaches to surface area estimation results in multiple orders of magnitude variation in RSA values (Bourg et al, 2015, Beckingham et al, 2016. In reactive transport simulations, variations in mineral reactive surfaces areas result not only in discrepancies in mineral reaction rates, but porosity and reactive plume evolution as well (Gaus et al, 2008, Atchley et al, 2014.…”

The Relevance of Geochemical Tools to Monitor Deep Geological CO2 Storage Sites

“…A simplified geochemical reactivity model is generally associated with building a detailed 2D or 3D fluid flow reservoir model, while a detailed description of the CO 2 /fluid/rock interactions with complex mineralogical assemblages and reaction kinetics is required for batch modelling (Gaus et al, 2008). Even though many kinetic data and rate laws are described in the literature (Plummer et al, 1978;Lasaga et al, 1994), the complexity of the system makes it difficult to acquire accurate data.…”