CO2 reaction with hydrated class H well cement under geologic sequestration conditions: effects of flyash admixtures.
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 microD. 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.
Kutchko
Barbara G
BG
National Energy Technology Laboratory, United States Department of Energy, Pittsburgh, Pennsylvania 15236, USA.
Strazisar
Brian R
BR
Huerta
Nicolas
N
Lowry
Gregory V
GV
Dzombak
David A
DA
Thaulow
Niels
N
D002244:Carbon / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D060729:Coal Ash; D003252:Construction Materials; D055593:Geological Phenomena; D006244:Hardness; D008855:Microscopy, Electron, Scanning; D052638:Particulate Matter / Q000737:chemistry*; D014057:Tomography, X-Ray Computed; D014867:Water / Q000737:chemistry*
D060729:Coal Ash; D052638:Particulate Matter; D014867:Water; D002245:Carbon Dioxide; D002244:Carbon