CCS and Power Systems
Carbon Storage - Geologic Storage Technologies and Simulation and Risk Assessment
Wellbore Seal Repair Using Nanocomposite Materials
Performer: University of New Mexico
Project No: FE0009562
Wells used to inject CO2 and monitor carbon storage sites are completed with cement and steel piping that is designed to seal the wellbore and eliminate pathways for the CO2 to migrate out of the storage formation. These seals can be compromised if voids are present or the steel or cement degrades and cracks, necessitating methods to repair leakage pathways that can potentially facilitate migration of CO2. Researchers at the University of New Mexico (UNM) are examining ways to repair leakage pathways by modifying polymer cements with various nanomaterials to produce polymer-cement nanocomposites that have superior repair characteristics compared to conventional materials.
The first phase of this research effort involves modifying polymer-cement slurries with various nanomaterials to increase their long-term performance in preventing CO2 leakage through the wellbore. Bond strength and fracture toughness testing will be conducted on the repair material bonded to the steel and cement. The slurries will be evaluated at the macroscale to determine their rheological properties, bond strength, fracture toughness, permeability, and durability against CO2 and brine water containing CO2 (Figure 1). Microstructural investigations of these nanocomposites will beconducted using nuclear magnetic resonance, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and nanoscratch tests.
The second phase involves testing the ability of select nanocomposite materials developed in the first phase to repair simulated flawed seal systems (Figure 2). Seal systems, composed of a casing (well pipe) set into a sheath of conventional well cement, will be created and various flaws (voids and fractures) will be incorporated into the cement and the cement-casing interface (corroded casing and artificially de-bonded interfacial regions). The samples will be placed in a pressure cell that mimics the pressures and temperatures found at CO2 storage depths and repair effectiveness will be measured. Post-test samples also will be examined for repair effectiveness and bond testing. The outcome will be an evaluation of the ability of the nanocomposite materials to repair flaws within the wellbore. The ability of the repair material to withstand supercritical CO2 will also be tested using a specialized system capable of delivering mixtures of CO2 and water at high pressures and specified flow rates.