CLIMIT-Forskning, utvikling og demo av CO2-håndtering

Enabling carbon capture and storage (CCS) is important for reducing the problem of global warming due to man-made CO2 emissions. Storage is achieved by injecting CO2 through wells in suitable geological formations. A prerequisite is that the storage site is safe, implying that the injected gas stays in the sub-surface and does not leak back to the atmosphere. The Norwegian Continental Shelf is a promising candidate for large scale CO2 storage. However, the area has many wells that are plugged and abandoned, since they are no longer used for oil and gas production. These wells are potential leakage points, and their integrity is therefore essential for storage safety. Due to a lack of affordable methods for assessing their integrity, such wells are all treated as "high risk" when evaluating possible storage locations. This leads operators to discard drilled regions from CO2 storage despite the wealth of subsurface information available there. To optimally exploit available storage capacity on the Norwegian Continental Shelf, it is therefore necessary to find a cost-efficient way of reliably assessing the integrity of wells without having to enter them. Such a remote monitoring option would be a game changer for CO2 storage, as it would not only increase storage options by allowing leakage risk assessment of plugged wells but would also allow continuous well integrity monitoring during operations, thereby ensuring targeted remediation and condition-based well intervention schemes. A first step towards this goal is to study the transmission of various signals along well construction materials (casing and cement), and how they can be emitted, detected and interpreted to create a well integrity report. The XMAS project combined numerical studies, experiments, and engineering work to determine which excitation methods and signals are most promising for remote well integrity assessment, and it studied how future wells can be constructed to facilitate remote monitoring. The project investigated the potential of non-invasive well monitoring methods and the corresponding data that can be generated. The focus has been mainly on seismic and electromagnetic signals. This included looking at different acquisition configurations like surface or sea floor acquisitions and evaluating the possibility to use the well casing as an antenna (for electromagnetic signals). The work performed resulted in a database of modelled cases ranging from simple to advanced cases considering realistic well geometries. This was crucial to understand the potential and limitations of different non-invasive sensing techniques. In parallel, a desktop workflow combining well integrity assessment, numerical modelling, and lab experiments to assess the need for non-invasive geophysical monitoring has been developed and applied to an example from the Smeaheia Structure in the Northern North Sea. XMAS also investigated how to link available data and measurable signals to the identification of well integrity issues. It studied (i) how available information about wells and P&A reports can be translated into a qualitative assessment of the well integrity issues, and (ii) how measurable signals using non-invasive monitoring techniques can be linked to the quantitative assessment of well integrity issues. Two methodologies have been developed: one for quick well screening based on the analysis of publicly available information from well completion reports and a machine learning based approach for location and classification of well damage. XMAS also studied and proposed an experimental set up at laboratory scale to carry out the feasibility of detection of fracture from tomographic measurements on sample plugs. It finally performed an engineering study of the changes necessary to next generation well systems for enabling the application in the field of monitoring techniques including techniques for non-invasive monitoring. The study highlighted that (i): direct and near-field remote integration to existing infrastructure is likely possible at limited complexity & cost, (ii)the integration level is depending on well condition and status, and (iii): the developed methods and concepts should form the basis for future demonstration. XMAS has helped SINTEF and Aker Solutions build a significant expertise within the topic of well integrity using non-invasive monitoring and establish new follow-up collaborations with several industry partners and leading research groups on the topic world-wide. The project partners strongly believe that non-invasive (and thus cost-effective) monitoring of legacy wells will play a key role to "unlock" the already identified huge capacity for storage on the Norwegian Continental Shelf.

SINTEF and Aker Solutions have built significant expertise within the topic of well integrity using non-invasive monitoring and has also, thanks to this project, established connections to several industry partners and leading research groups on the topic world-wide. The importance of being able to quantify the well integrity status of a well without the need to re-open it is significant. For obvious reasons, large scale offshore CO2 storage is more feasible in "known" areas meaning already drilled areas e.g., depleted O&G reservoirs or decommissioned fields. This has several advantages: (i) they are well characterized, (ii) the pressure is low, reducing injection risk, (iii) infrastructure like wells and pipelines is already in place, and (iv) it may be possible to extract more hydrocarbons (CO2 enhanced oil recovery). The risks associated with possible issues with legacy wells can however be a showstopper. Non-invasive (and thus cost-effective) monitoring of legacy wells can therefore play a key role to "unlock" the huge capacity for storage on the Norwegian Continental Shelf already identified. In addition to the original plans for the use of non-invasive geophysical monitoring to report well integrity status, it became clear during the project that a tool for quick screening can be very useful for the storage resource exploration phase where a ranking of different storage options is required. The development of the tool has benefited from synergies with the Tophole KPN project. We foresee a clear need to further develop both methodologies (quick screening and monitoring) to answer the needs of CO2 and erergy storage operators.

Wells are the "gate keepers" of stored CO2, and their integrity dictate to a large degree the overall storage safety. Some wells penetrating prospective CO2 storage sites are plugged and abandoned, and their wellhead and upper casing pipes are severed several meters below seafloor. Due to a lack of methods for assessing their integrity, such wells are all treated as "high risk" when evaluating possible storage locations. This leads operators to discard heavily drilled regions from CO2 storage - despite the wealth of information available on the subsurface here. To optimally exploit available storage capacity on the Norwegian Continental Shelf, it is therefore necessary to find a way of reliably assessing the integrity of wells without having to enter them with logging tools. Such a remote (non-invasive) monitoring option would be a game changer for CO2 storage, as it would not only increase storage options by allowing leakage risk assessment of plugged wells, it would also allow continuous well integrity monitoring during operations - and thereby ensure targeted remediation and condition-based well intervention schemes. A first step for reaching this goal is to study the transmission of various signals along well construction materials (casing and cement), and how they can be imposed, detected and interpreted to draw up a well integrity report. This is the goal in the current project, which combines numerical studies, experiments and engineering work. It will determine which excitation methods and signals are most promising for remote well integrity assessment, and it will study ways future wells can be constructed (with different materials) to optimize remote monitoring possibilities.