Assessment of two-phase flow on the chemical alteration and sealing of leakage pathways in cemented wellbores. (February 2018)

• Record Type: Journal Article
• Authors: Iyer, Jaisree; Walsh, Stuart D.C.; Hao, Yue; Carroll, Susan A.
• Is Part Of: International journal of greenhouse gas control. Volume 69(2018)
• Page Start: 72
• Page End: 80
• Publication Date: 2018-02
• Subjects: Carbon storage -- Two-phase flow -- Wellbore integrity -- Cement-CO2 reactions; Greenhouse gases -- Environmental aspects -- Periodicals; Air -- Purification -- Technological innovations -- Periodicals; Gaz à effet de serre -- Périodiques; Gaz à effet de serre -- Réduction -- Périodiques; Air -- Purification -- Technological innovations; Greenhouse gases -- Environmental aspects; Periodicals; 363.73874605
• DOI: 10.1016/j.ijggc.2017.12.001
• Languages: English
• ISSNs: 1750-5836

Abstract

Graphical abstract: Highlights: Coupled two-phase flow to quantify leakage risk in CO2 storage sites. Aperture and brine residence time are critical parameters that determine sealing. Relative permeability and saturation determine location on a sealing map. Sealing time influenced by aperture for saturation independent reactive surface area. Most parameters become important when reactive surface area depends on saturation. Abstract: Wellbore leakage tops the list of perceived risks to the long-term geologic storage of CO2, because wells provide a direct path between the CO2 storage reservoir and the atmosphere. In this paper, we have coupled a two-phase flow model with our original framework that combined models for reactive transport of carbonated brine, geochemistry of reacting cement, and geomechanics to predict the permeability evolution of cement fractures. This addition makes the framework suitable for field conditions in geological storage sites, permitting simulation of contact between cement and mixtures of brine and supercritical CO2 . Due to lack of conclusive experimental data, we tried both linear and Corey relative permeability models to simulate flow of the two phases in cement fractures. The model also includes two options to account for the inconsistent experimental observations regarding cement reactivity with two-phase CO2 -brine mixtures. One option assumes that the reactive surface area is independent of the brine saturation and the second option assumes that the reactive surface area is proportional to the brine saturation. We have applied the model to predict the extent of cement alteration, the conditions under which fractures seal, the time it takes to seal a fracture, and the leakage rates of CO2 and brine when damage zones in the wellbore are exposed to two-phase CO2 -brine mixtures. Initial brine residence time and the initial fracture aperture are critical parameters that affect the fracture sealing behavior. We also evaluated the importance of the model assumptions regarding relative permeability and cement reactivity. Our results illustrate the need to understand how mixtures of carbon dioxide and brine flow through fractures and react with cement to make reasonable predictions regarding well integrity. For example, a reduction in the cement reactivity with two-phase CO2 -brine mixture can not only significantly increase the sealing time for fractures but may also prevent fracture sealing.