Browsing by Author "Kirksey, J."

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Enhancing wellbore cement integrity with microbially induced calcite precipitation (MICP): A field scale demonstration
(2018-12) Phillips, Adrienne J.; Troyer, E.; Hiebert, R.; Kirkland, Catherine M.; Gerlach, Robin; Cunningham, Alfred B.; Spangler, Lee H.; Kirksey, J.; Rowe, W.; Esposito, R.
The presence of delaminations, apertures, fractures, voids and other unrestricted flow channels in the wellbore environment substantially reduces wellbore integrity. Compromised cement may cause a loss of zonal isolation leading to deleterious flow of fluids between zones or to the surface with multiple potential negative impacts including: loss of resource production, reduction of sweep efficiency in EOR operations, and regulatory non-compliance. One potential solution to enhance wellbore integrity is microbially induced calcite precipitation (MICP) to plug preferential flow pathways. MICP is promoted with micrometer-sized organisms and low viscosity (aqueous) solutions thereby facilitating fluid transport into small aperture, potentially tortuous leakage flow paths within the cement column. In this study, MICP treatment of compromised wellbore cement was demonstrated at a depth interval of 310.0–310.57 m (1017–1019 feet) below ground surface (bgs) using conventional oil field subsurface fluid delivery technologies (packer, tubing string, and a slickline deployed bailer). After 25 urea/calcium solution and 10 microbial (Sporosarcina pasteurii) suspension injections, injectivity was reduced from the initial 0.29 cubic meters per hour (m3/h) (1.28 gallons per minute (gpm)) to less than 0.011 m3/h (0.05 gpm). The flow rate was decreased while maintaining surface pumping pressure below a maximum pressure of 81.6 bar (1200 psi) to minimize the potential for fracturing a shale formation dominant in this interval. The pressure decay immediately after each injection ceased decreased after MICP treatment. Comparison of pre- and post-test cement evaluation logs revealed substantial deposition of precipitated solids along the original flow channel. This study suggests MICP is a promising tool for enhancing wellbore cement integrity.
Fracture Sealing with Microbially-Induced Calcium Carbonate Precipitation: A Field Study
(2016-04) Phillips, Adrienne J.; Cunningham, Alfred B.; Gerlach, Robin; Hiebert, Dwight Randall; Hwang, Chiachi; Lomans, B. P.; Westrich, Joseph; Mantilla, C.; Kirksey, J.; Esposito, R.; Spangler, Lee H.
A primary environmental risk from unconventional oil and gas development or carbon sequestration is subsurface fluid leakage in the near wellbore environment. A potential solution to remediate leakage pathways is to promote microbially induced calcium carbonate precipitation (MICP) to plug fractures and reduce permeability in porous materials. The advantage of microbially induced calcium carbonate precipitation (MICP) over cement-based sealants is that the solutions used to promote MICP are aqueous. MICP solutions have low viscosities compared to cement, facilitating fluid transport into the formation. In this study, MICP was promoted in a fractured sandstone layer within the Fayette Sandstone Formation 340.8 m below ground surface using conventional oil field subsurface fluid delivery technologies (packer and bailer). After 24 urea/calcium solution and 6 microbial (Sporosarcina pasteurii) suspension injections, the injectivity was decreased (flow rate decreased from 1.9 to 0.47 L/min) and a reduction in the in-well pressure falloff (>30% before and 7% after treatment) was observed. In addition, during refracturing an increase in the fracture extension pressure was measured as compared to before MICP treatment. This study suggests MICP is a promising tool for sealing subsurface fractures in the near wellbore environment.