Formation Damage in CO2 Storage Wells – The Same, But Different

Abstract

Abstract In many respects formation damage challenges in CO2 storage wells are similar to those in conventional oil and gas production wells and water and gas injection wells. But there are some differences from "conventional" well formation damage challenges. This paper outlines some issues specific to CO2 injection wells and proposes changes in focus prior to and during drilling and completion of these wells. CCS (Carbon Capture and Storage) store can generally be split in to two categories – saline aquifers and depleted hydrocarbon reservoirs. Wells drilled and/or completed in these stores share some well injectivity challenges with conventional wells but also have some challenges specific to the store properties. In conventional injection wells it is generally accepted that well clean-up or back production prior to injection is beneficial as formation damage necessarily induced during well drilling and clean-up may be partially or fully removed. For saline aquifers and depleted hydrocarbon stores, well clean-up is normally not possible or practical. Direct injection after well completion is often required. A new workflow capturing the key steps required to assure optimum well injectivity over the well life cycle has been developed and will be outlined in the paper. This includes but is not limited to: detailed analysis of CO2 phase behaviour in and beyond the lower completion; lower completion selection criteria specific to CO2 stores; laboratory testing and modelling focussed on CO2 store formation damage challenges; direct injection challenges and successful mitigations; ice scale and hydrate challenges in CO2 storage wells. With increasing focus on CO2 storage globally, the workflow outlined presents an integrated approach to formation damage challenges. It demonstrates that although many of the challenges are similar to those in conventional wells, there are also some that are different and unique – the same, but different!