Advanced Well Integrity Experiment and Tools to Repurpose Legacy Wells for CO2 Injection

Abstract

Storing CO2 in Depleted Oil & Gas Fields (DOGF) is likely to help meet climate targets by enabling faster and cheaper deployment of geological carbon storage when compared to storage in saline aquifers. In the case of DOGF, large investments have already been made and can be capitalized on. For example, the data acquisitions campaigns, the reservoir characterization studies, and the drilling and construction of exploration, production and monitoring wells have already been performed. To make these time and cost-reduction possible, the integrity of legacy wells must be assessed to ensure that they are competent to contain CO2 and, for some wells, that they can be re-purposed for CO2 injection. To achieve this, the main drivers of integrity loss, debonding and fracturing, must be better understood and tools for their prediction must be developed. With this in mind, TotalEnergies has developed a novel well experiment that aims to reproduce the field conditions of a legacy well over its lifetime. This includes, the construction of the well, the oil or gas depletion of the reservoir, the injection of CO2 and finally, the long-term containment of CO2. The experiment consists of a downscaled casing, a cored formation and a cement sheath cured under field conditions (in pressure & temperature). The experiment can apply up to 700 bar of casing pressure, horizontal confinement pressure and pore pressure while being able to cool the experiment down to -30°C and heat it up to 130°C. Fracturing and debonding are assessed with deformation gauges, acoustic sensors, fluid pressure & temperature monitoring and CT-Scans. Finally, experiments are supported with analytical and numerical modelling tools which allow the prediction of fracturing and debonding inside the experiment. With the numerical tool, fracture initiation, propagation and interactions are captured, this enables detailed predictions of well integrity and the identification of leakage pathways. This work presents the experimental configuration as well as the tools employed.

Keywords: Well integrity, CO2 storage, CCUS, legacy wells, FDEM, FEMDEM, debonding, fracturing, portland cement, cement stress