Understanding the Role of Scale Management in Carbon Capture, Utilisation and Storage (CCUS)

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Abstract Recent trends towards carbon net zero and the push to develop renewable energy as an alternative to fossil fuels have resulted in major environmental focus on de-carbonisation projects with an emphasis on carbon capture, utilisation, and storage (CCUS). Both carbon capture and utilisation (CCU) and carbon capture and storage (CCS), capture carbon dioxide (CO2) from heavy industries and air, by direct air capture (DAC), and transport it to sites by rail, boat, or pipeline for injection into geological reservoirs for permanent storage and/or enhanced oil recovery (EOR). A range of issues related to mineral scale deposition can be encountered that impact the efficiency of CO2 injection and utilisation/storage. These can include calcium carbonate deposition during CO2 capture in a calcium looping process, halite (NaCl) precipitation during supercritical dry CO2 injection and CO2 leakage due to the dissolution of carbonate cements and minerals in reservoir rocks which impact both cement and reservoir rock integrity. During CO2 utilisation for EOR, downhole and topside calcium carbonate deposition can occur in the production facilities. Effective scale management strategies are essential to maintain a safe, sustainable, and efficient CCUS process. It will also be necessary to minimise CO2 footprint during the whole lifecycle by making it less energy demanding. Scale control can be based on continuous scale inhibitor injection or squeeze treatments. Additionally, for wellbore integrity and to better isolate the well from the formation, sulphate scale may deliberately be deposited to provide extra strength to cements impacted by contact with CO2. This intentional precipitation of sulphate minerals needs special attention to be paid to ensure precipitation in the correct location. This involves consideration of pumping equipment, well completion, and rock type as they impact the deployment process to control the location, rate and mass of sulphate mineral deposition. This paper reviews the scale issues arising during CCUS including calcium carbonate deposition during carbon capture, halite and microbial induced calcium carbonate deposition during CO2 injection. Both conventional and unconventional scale management approaches are considered including treatments with and without scale inhibitors. The impact of well completion, cement type, and CO2 injection rates on CCUS and the selected scale management process are discussed. In addition, laboratory data for controlled barium sulphate (BaSO4) mineral scale deposition is presented coupled with field designs for CO2 utilisation through disposal in injection water in a calcareous sandstone and CO2 water alternating gas (WAG) injection in a carbonate reservoir.