Rate of CO₂ Attack on Hydrated Class H Well Cement under Geologic Sequestration Conditions

Abstract

Experiments were conducted to study the degradation of hardened cement paste due to exposure to CO2 and brine under geologic sequestration conditions (T = 50 degrees C and 30.3 MPa). The goal was to determine the rate of reaction of hydrated cement exposed to supercritical CO2 and to CO2-saturated brine to assess the potential impact of degradation in existing wells on CO2 storage integrity. Two different forms of chemical alteration were observed. The supercritical CO2 alteration of cement was similar in process to cement in contact with atmospheric CO2 (ordinary carbonation), while alteration of cement exposed to CO2-saturated brine was typical of acid attack on cement. Extrapolation of the hydrated cement alteration rate measured for 1 year indicates a penetration depth range of 1.00 +/- 0.07 mm for the CO2-saturated brine and 1.68 +/- 0.24 mm for the supercritical CO2 after 30 years. These penetration depths are consistent with observations of field samples from an enhanced oil recovery site after 30 years of exposure to CO2-saturated brine under similar temperature and pressure conditions. These results suggest that significant degradation due to matrix diffusion of CO2 in intact Class H neat hydrated cement is unlikely on time scales of decades.

Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

“…7.18 Calculated pH profiles from 1 day to 6 weeks, simulating the work of (Rimmelé et al, 2008), Kutchko et al (Kutchko et al, 2008). .…”

“…. 126 7.32 Calculated profiles of solid volume compounds after 9 days of exposure for the simulation of (Kutchko et al, 2008). 7.36 SEM-BSE image for the sample after 9 days of exposure to CO 2 -saturated brine, cited from (Kutchko et al, 2008) …”

“…The precipitated calcium carbonate could also dissolve in some cases, leaving a high porous silica gel (Duguid and Scherer, 2010). In other cases, the calcium carbonate will not dissolve and protect the inner side of the cement from further degradation (Duguid and Scherer, 2010;Kutchko et al, 2008).…”

“…The authors have intended to simulate the conditions of CO 2 -saturated water which were tested in Duguid's experiments (Duguid and Scherer, 2010). In the recently published work of (Huet et al, 2011), experimental works of cement pastes exposed to CO 2 -saturated brine, from (Duguid and Scherer, 2010;Rimmelé et al, 2008;Kutchko et al, 2008) were simulated and compared briefly. Huet et al concluded that the reactivity is either controlled by Ca/CO 2 diffusion, or stops because of calcium carbonate caused clogging.…”

Strength Development and Carbonation Characteristics of Slag Cement/Class C Fly Ash blended CO2Injection Well Sealant

“…(2), leads to a decrease in porosity and permeability as a result of the larger molar volume of CaCO 3 relative to Ca(OH) 2 (Carey et al, 2007;Rimmelet al, 2008;Liteanu and Spiers, 2011). (2) These pore-sealing effects caused by reactions between sealant and CO 2 are considered not persistent but limited (Kutchko et al, 2007(Kutchko et al, , 2008. Not only long-term integrity, but also early strength development is important in main- Corresponding author : ihwang@pusan.ac.kr Received : 2016.…”