Equilibrium partial pressure of CO2 in Callovian–Oxfordian argillite as a function of relative humidity: Experiments and modelling

Abstract

, et al.. Equilibrium partial pressure of CO 2 in Callovian-Oxfordian argillite as a func-tion of relative humidity: experiments and modelling. Geochimica et Cosmochimica Acta, Elsevier, 2016Elsevier, , 186, pp.91-104. 10.1016Elsevier, /j.gca.2016 Accepted Manuscript This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractHaving previously demonstrated that the mineral assemblage of claystone can impose its pCO 2 under saturated conditions, we here study the effect of rock desaturation, i.e.the evaporation of pore water, on the partial pressure of CO 2 (pCO 2 ) in CallovianOxfordian argillite from the Paris Basin (France). In this new study, which combines experiments at room temperature and geochemical modelling, we examine the primary role of capillary forces on chemical equilibria for relative humidity values ranging between 50% and 100%. In particular we are able, without any fitting parameters, to model the experimental decrease of pCO 2 as a function of decreasing water content in the argillite. This application to a complex natural system not only confirms the theoretical concepts of geochemistry in capillary contexts, but is promising with respect to other systems, both natural (soil, rock) and industrial (ceramics, granular material).

Regeneration of capillary water in unsaturated zones

“…Recent experimental studies agree for CO 2 (Lassin et al, 2016) and O 2 (Lidon et al, 2018) gases and for salts (Hulin and Mercury, 2019).…”

Well integrity assessment by a 1:1 scale wellbore experiment: Exposition to dissolved CO 2 and overcoring

“…Two populations of samples are distinguished: 1) A first population of samples, the least perturbed, exhibit an almost similar range of pCO 2 around 14-16 mbar and the lowest ␦ 13 C of CO 2 between −12 and −7‰; values of 14-16 mbar remain higher than reference values measured in previous works (Lerouge et al, 2015). Recent experimental work provided evidence of an increase of pCO 2 with the relative humidity and the saturation state of the sample (Lassin et al, 2016). Reference pCO 2 were measured on samples from a drillhole drilled with Ar flux and without any resaturation, with a maximum relative humidity measured at ∼95%.…”

RTM for Waste Repositories

“…The reverse is true for K + when the cement material is made of low-pH cement. Still, in relation to the pH values, partial CO 2 pressures are far lower in cement materials than in the pore water of clay-rocks, where partial pressures of CO 2 that are higher than the atmospheric pressure (~10 −3 to ~10 −2 bars) are reported (Gailhanou et al 2009;Lassin et al 2016). Redox conditions are reducing in both claystone (Brendler et al 2003) and in reinforced steel cement materials (Aréna et al 2018).…”

“…In this regard, the RTM of waste repositories could benefit from the experience return of modeling in other systems such as CO 2 sequestration (Sin and Corvisier 2019, this volume). Another aspect of unsaturated porous media that is not yet widely treated in RTM relates to the dependence of chemical reactivity with regard to the water content, in particular looking at how the mineral and gas solubility and the aqueous speciation relate to capillary pressure at low water saturation (Lassin et al 2005(Lassin et al , 2011(Lassin et al , 2016. This process may be enhanced by the fact that some chemical reactions, such as steel corrosion and glass alteration, consume water; this coupled effect is only starting to be fully integrated in RTM codes (Seigneur et al 2018).…”