HR: 1340h
AN: GC13A-1222    [Abstracts]
TI: Analysis of the Wellbore Seal at Well 49-6 in the SACROC CO2 Enhanced Oil Recovery Field, West Texas
AU: * Carey, J W
EM: bcarey@lanl.gov
AF: Earth and Environmental Sciences and Chemistry Divisions Los Alamos National Laboratory, MS D462, Los Alamos, NM 87545 United States
AU: Wigand, M
EM: marcusw@lanl.gov
AF: Earth and Environmental Sciences and Chemistry Divisions Los Alamos National Laboratory, MS D462, Los Alamos, NM 87545 United States
AU: Chipera, S
EM: chipera@lanl.gov
AF: Earth and Environmental Sciences and Chemistry Divisions Los Alamos National Laboratory, MS D462, Los Alamos, NM 87545 United States
AU: WoldeGabriel, G
EM: wgiday@lanl.gov
AF: Earth and Environmental Sciences and Chemistry Divisions Los Alamos National Laboratory, MS D462, Los Alamos, NM 87545 United States
AU: Pawar, R
EM: rajesh@lanl.gov
AF: Earth and Environmental Sciences and Chemistry Divisions Los Alamos National Laboratory, MS D462, Los Alamos, NM 87545 United States
AU: Lichtner, P C
EM: lichtner@lanl.gov
AF: Earth and Environmental Sciences and Chemistry Divisions Los Alamos National Laboratory, MS D462, Los Alamos, NM 87545 United States
AU: Wehner, S
EM: Scott_Wehner@kindermorgan.com
AF: Kinder Morgan CO2 Company, L.P., 500 North Loraine, Suite 1175, Midland, TX 79701 United States
AU: Raines, M
EM: Michael_Raines@kindermorgan.com
AF: Kinder Morgan CO2 Company, L.P., 500 North Loraine, Suite 1175, Midland, TX 79701 United States
AU: Guthrie, G D
EM: gguthrie@lanl.gov
AF: Earth and Environmental Sciences and Chemistry Divisions Los Alamos National Laboratory, MS D462, Los Alamos, NM 87545 United States
AB: Long-term integrity of wellbore cements is one of the major concerns for geologic sequestration of CO₂. This paper presents analyses of cement core recovered from a well used in a long-term CO₂ enhanced oil recovery operation. A sidetrack system was used to obtain core from a 55 year-old well with 30 years of CO₂ exposure as both an injector and a producer at the SACROC unit (Permian Basin, Texas). The mineralogy, chemistry, and hydrologic properties were evaluated for evidence of degradation by CO₂. The recovered samples were located ~ 3 m above the contact with the reservoir. The recovered cement had permeabilities in the milliDarcy range and thus retained its capacity to prevent significant flow of CO₂. There was evidence for CO₂ migration along the casing-cement and cement-shale interfaces. The casing interface had a 1-2 mm thick rind of calcite-aragonite-halite. The CO₂ producing this rind may have traveled up the casing wall or may have infiltrated through the casing threads. The cement in contact with the shale (within 1 cm) was heavily carbonated to an assemblage of calcite, aragonite, vaterite and amorphous alumino-silica residue and was transformed to a distinctive orange color. The heavily carbonated region is separated from less altered cement by a narrow, dense zone of silica and carbonate deposition. The CO₂ for this carbonation process migrated from the cement-shale interface where the presence of shale fragments (wall cake) may have provided a fluid pathway. The carbonation reaction was associated with only small changes in the original cement chemistry including an increase in Na₂O and decrease in CaO and MgO with a slight enrichment in SiO₂. The carbonated zone also has a distinct carbon and oxygen stable isotope signature. Although the observed carbonation was intense, the measured hydrologic properties of the carbonated zone were not significantly different from those of relatively unaltered cement in adjacent parts of the core. Textural observations and numerical modeling indicate that the carbonation of the cement occurred by diffusion of CO₂-saturated brine from the cement-shale interface. A 1-D diffusion simulation using FLOTRAN was able to reproduce the general features of the carbonation zone including carbonate deposition, alteration of the cement, width of the zone, and the presence of a dense interface with the less altered cement. The SACROC observations show, at least for the single well investigated, that Portland-based cement used in a CO₂ reservoir environment can maintain hydrologic integrity for a period of 30 years despite significant carbonate mineralization. However, we were unable to quantify the amount of CO₂ migration that occurred along cement interfaces with the casing and shale caprock. The quality of these interfaces appears to be the most critical issue in the performance of wellbore systems in a CO₂ sequestration reservoir.
DE: 0545 Modeling (4255)
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1012 Reactions and phase equilibria (3612, 8412)
DE: 1694 Instruments and techniques
DE: 1699 General or miscellaneous
SC: Global Climate Change [GC]
MN: Fall Meeting 2005