Development and testing of novel cement designs for enhanced CCS well integrity

The CEMENTEGRITY project seeks to develop and test better materials for sealing wellbores exposed to CO2 stored in underground reservoirs. Such materials should 1) prevent leakages from forming; 2) demonstrate self-healing behaviour when leakages do form; 3) have a smaller environmental footprint than currently used materials. The leakage of CO2 through or along wellbores has been identified as one of the main challenges to secure underground CO2-storage. Currently used materials for sealing wellbores are commonly based on Ordinary Portland Cement, and the integrity of these material can be a vulnerability during CO2-injection and -storage. Leakages may form through the cement, or along the cement-steel or cement-rock interfaces, as the result of chemical, thermal, or mechanical effects. In order to successfully develop improved sealing materials, we need to identify critical properties that will ensure seal integrity. We also need to develop practical methods for measuring these properties under realistic conditions, and models that can be used for extrapolation. The CEMENTEGRITY project will perform experimental research that addresses the chemical, thermal, and mechanical mechanisms that may damage wellbore integrity during CO2-injection and -storage. We will test a range of different sealant material compositions. We will support this experimental work with numerical modelling. Through these activities, we will identify key properties that ensure long-term integrity of wellbore sealing materials, and we will also identify suitable methods for measuring these properties. Our findings can then be applied when developing new sealing materials for CO2-storage, to ensure the long-term integrity of underground CO2-storage reservoirs.

The leakage of CO2 through or along wellbores has been identified as one of the main challenges to secure subsurface CO2-storage. Currently used wellbore sealants, commonly based on Ordinary Portland Cement, can be a large vulnerability during CO2-injection and -storage. Leakages may form through the cement, or along the cementsteel or cement-rock interfaces, as the result of chemical, thermal, or mechanical effects. Therefore, better sealants need to be developed that can prevent leakages from forming, and that demonstrate self-healing capabilities when leakage pathways do form. In order to successfully develop such materials, critical properties need to be identified that will ensure seal integrity, and practical methods and procedures for measuring these properties under in-situ conditions need to be developed, along with models for their extrapolation. CEMENTEGRITY will address the chemical, thermal and mechanical mechanisms that may damage wellbore integrity during CO2-injection and -storage, through experimental research on 5 different sealant compositions. WP1 will perform flow-through experiments with CO2 and CO2 bearing H2S to test changes in permeability and mechanical properties. WP2 will expose sealants to supercritical CO2 with H2S and other impurities, to investigate changes in composition. WP3 will expose sealant specimens to thermal shocks and cycling, to observe thermal cracking and annulusformation. WP4 will develop numerical models to extrapolate experimental results. WP5 will measure sealant-steel bond strengths, and develop electrical resistivity methods for in-situ monitoring of sealant and interface integrities. WP6 will develop a novel, rock-based geopolymer sealant specifically for CCS applications. Based on these WPs, WP7 will identify key properties to ensure long-term integrity of wellbore seals during CCS, as well as suitable methods for measuring these properties. These methods can then be applied when developing new sealants for CCS.