CO2 Reaction with Hydrated Class H Well Cement under Geologic Sequestration Conditions: Effects of Flyash Admixtures

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• 作者：Barbara G. Kutchko ; Brian R. Strazisar ; Nicolas Huerta ; Gregory V. Lowry ; David A. Dzombak ; Niels Thaulow
• 刊名：Environmental Science & Technology
• 出版年：2009
• 出版时间：May 15, 2009
• 年：2009
• 卷：43
• 期：10
• 页码：3947-3952
• 全文大小：352K
• 年卷期：v.43,no.10(May 15, 2009)
• ISSN：1520-5851

文摘

The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO₂ and CO₂-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing wells on CO₂ storage integrity. The pozzolan additive chosen, Type F flyash, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolan−cement blends were exposed to supercritical CO₂ and CO₂-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170−180 mm for both the CO₂-saturated brine and supercritical CO₂ after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO₂, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 μD. Analyses of 50:50 pozzolan−cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO₂, which are consistent with our laboratory findings.