title: Wellbore Cement Porosity Evolution in Response to Mineral Alteration during CO2Flooding.
abstract: Mineral reactions during CO2sequestration will change the pore-size distribution and pore surface characteristics, complicating permeability and storage security predictions. In this paper, we report a small/wide angle scattering study of wellbore cement that has been exposed to carbon dioxide for three decades. We have constructed detailed contour maps that describe local porosity distributions and the mineralogy of the sample and relate these quantities to the carbon dioxide reaction front on the cement. We find that the initial bimodal distribution of pores in the cement, 1-2 and 10-20 nm, is affected differently during the course of carbonation reactions. Initial dissolution of cement phases occurs in the 10-20 nm pores and leads to the development of new pore spaces that are eventually sealed by CaCO3precipitation, leading to a loss of gel and capillary nanopores, smoother pore surfaces, and reduced porosity. This suggests that during extensive carbonation of wellbore cement, the cement becomes less permeable because of carbonate mineral precipitation within the pore space. Additionally, the loss of gel and capillary nanoporosities will reduce the reactivity of cement with CO2due to reactive surface area loss. This work demonstrates the importance of understanding not only changes in total porosity but also how the distribution of porosity evolves with reaction that affects permeability.
authors.affiliation: Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Michael C
authors.identifier: 0000-0003-1792-6881
authors.initials: MC
authors.lastname: Cheshire
authors.affiliation: Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Stack
authors.affiliation: Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: J William
authors.initials: JW
authors.lastname: Carey
authors.affiliation: Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Anovitz
authors.affiliation: Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Prisk
authors.affiliation: Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Jan
authors.initials: J
authors.lastname: Ilavsky
mesh_terms: D002119:Calcium Carbonate; D002245:Carbon Dioxide; D002254:Carbonates; D003252:Construction Materials; D016062:Porosity
chemical_list: D002254:Carbonates; D002245:Carbon Dioxide; D002119:Calcium Carbonate