Gregory V. Lowry

Effect of CO₂ and Brine Solutions on the Integrity of Well-bore Cement Cured at In situ Temperature and Pressure

Funding Agencies
Department of Energy-National Energy Technology Laboratory

Collaborators
Brian Strazisar (NETL)

David Dzombak

Publications
Kutchko, B., Strazisar, B., Dzombak, D., Lowry, G., Thaulow, N. (2007). “Degradation of Wellbore Cement by CO₂ under Geologic Sequestration Conditions”. Environ. Sci. Technol., 41 (13) 4787-4792.

Abstract

Geologic carbon sequestration involves injection of large quantities of carbon dioxide (CO₂) into geologic formations such as depleted or active oil and gas reservoirs, unmineable coalseams, or deep saline aquifers. A significant issue with geologic sequestration is the verification of long term storage by identifying and monitoring leaks and other deterioration of storage integrity over time. The majority of locations that are being considered for CO₂ injection are in areas that have a history of oil, natural gas, and/or coalbed methane production. As a result, these formations are typically punctured by a significant number of wells. These wells are the most likely route for leakage of CO₂ from geologic carbon sequestration.

To make responsible decisions about where to inject CO₂, is very important to understand the chemical interactions between injected CO₂ and existing cements that could potentially lead to leakage. The objective of this study are to determine the rate and dynamics of acid attack from CO₂ at high temperature and pressure on cement cured at temperatures and pressures representative of in situ conditions.

Scanning Electron Microscope (SEM) backscattered electron (BSE) image of cement cured for 28 days at 50 °C and 30.3 MPa and exposed 9 days to aqueous CO₂ at 50 °C and 30.3 MPa. This figure illustrates typical degradation observed in class H neat cement. The degraded region can be divided into three distinct zones (see below).

Schematic showing the dissolution and calcium migration and the formation of distinct zones in the cement. Equation numbers refer to chemical reactions that occur at each front as detailed in the text. Note: in the cement structure, local pH is buffered by CaCO_3(s) and Ca(OH)_2(s).

Greg Lowry Home | Dept. Civil & Env.

Engr. | Modified: Sept 2007