Chemical and mechanical properties of wellbore cement altered by CO 2-rich brine using a multianalytical approach

Harris E. Mason, Wyatt L. Du Frane, Stuart D.C. Walsh, Zurong Dai, Supakit Charnvanichborikarn, Susan A. Carroll

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Defining chemical and mechanical alteration of wellbore cement by CO 2-rich brines is important for predicting the long-term integrity of wellbores in geologic CO2 environments. We reacted CO 2-rich brines along a cement-caprock boundary at 60 C and pCO 2 = 3 MPa using flow-through experiments. The results show that distinct reaction zones form in response to reactions with the brine over the 8-day experiment. Detailed characterization of the crystalline and amorphous phases, and the solution chemistry show that the zones can be modeled as preferential portlandite dissolution in the depleted layer, concurrent calcium silicate hydrate (CSH) alteration to an amorphous zeolite and Ca-carbonate precipitation in the carbonate layer, and carbonate dissolution in the amorphous layer. Chemical reaction altered the mechanical properties of the core lowering the average Young's moduli in the depleted, carbonate, and amorphous layers to approximately 75, 64, and 34% of the unaltered cement, respectively. The decreased elastic modulus of the altered cement reflects an increase in pore space through mineral dissolution and different moduli of the reaction products.

Original languageEnglish
Pages (from-to)1745-1752
Number of pages8
JournalEnvironmental Science & Technology
Issue number3
Publication statusPublished - 5 Feb 2013
Externally publishedYes

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