Abstract

Planning for Carbon Capture and Storage (CCS) infrastructure needs to address the impact of store uncertainties and store flow variability on infrastructure costs and availability. Key geological storage properties (pressure, temperature, depth and permeability) can affect injectivity and lead to variations in CO2 flow, which feed back into the pipeline transportation system. In previous storage models, the interface between the reservoir performance and the transportation infrastructure is unclear and the models are unable to provide details for flow and pressure management within a transportation network in response to changes in the operation of storage sites. Variation in storage demand due to daily and seasonal variations of fossil fuels uses and by extension CO2 flow is also likely to influence transportation infrastructure availability and the capacity to deliver. This work evaluates, at the level of infrastructure planning, the impact of geological uncertainty on CCS pipeline transportation and injection infrastructure. The analysis presented shows how to consider uncertainty in store properties in combination with CO2 flow variability to estimate the likely impact on pipeline infrastructure design. The operational envelope of the storage site infrastructure is estimated by combining the Darcy flow analysis of simple reservoir models with rigorous process simulation of the storage site wells. The proximity of wellhead conditions to the CO2 equilibrium line and the maximum velocities inside the well constrain the operational envelope of the storage site and limit the ability of the storage site infrastructure to handle CO2 flow variation. These factors, which are significantly influenced by variations in subsurface conditions, have also an impact on the design of the offshore pipeline infrastructure, needing to accommodate changes in pressure delivery requirements. Based on the evaluation of examples developed for different offshore transportation scenarios relevant to the United Kingdom, detailed insight on the expected impacts of store properties on pipeline transportation infrastructure design and operation is provided. For instance, it is found that enabling storage site flexibility is simpler in stores with an initial pressure above 20MPa. Given reductions in reservoir permeability, the requirements for pressure delivery are strongly dependent on the store temperature. Although the analysis is performed for specific geological characteristics in the North Sea the evaluation methodology is transferable to other locations and can be used for site screening to identify sites which are more flexible in terms of uncertainty in store performance. Document type: Article

Abstract

This paper describes two indoor shelter models – an analytical model and a Computational Fluid Dynamics (CFD) model - that can be used to predict the level of infiltration of carbon dioxide (CO2) into a building following a release from an onshore CO2 pipeline. The motivation behind the development of these models was to demonstrate that the effects of shelter should be considered as part of a Quantitative Risk Assessment (QRA) for CO2 pipeline infrastructure and to provide a methodology for considering the impact of a CO2 release on building occupants.A key component in the consequence modelling of a release from a CO2 pipeline is an infiltration model for CO2 into buildings which can describe the impact on people inside buildings during a release event. This paper describes the development of an analytical shelter model and a CFD model which are capable of predicting the change in internal concentration, temperature and toxic load within a single roomed building that is totally engulfed by a transient cloud of gaseous CO2. Application of the models is demonstrated by comparison with experimental measurements of CO2 accumulation in a building placed in the path of a drifting cloud of CO2. The analytical and CFD models are shown to make good predictions of the average change in internal concentration. Furthermore, it is demonstrated that the effects of shelter should be taken into account when conducting QRA assessments on CO2 pipelines. Document type: Article

Abstract

In Carbon Capture, Usage and Storage (CCUS) schemes, Carbon Dioxide (CO2) is captured from large scale industrial emitters and transported to geological sites for storage. The most efficient method for the transportation of CO2 is via pipeline in the dense phase. CO2 is a hazardous substance which, in the unlikely event of an accidental release, could cause people harm. To correspond with United Kingdom (UK) safety legislation, the design and construction of proposed CO2 pipelines requires compliance with recognised pipeline codes. The UK code PD-8010-1 defines the separation distance between a hazardous pipeline and a nearby population as the minimum distance to occupied buildings using a substance factor. The value of the substance factor should be supported by the results of a Quantitative Risk Assessment (QRA) approach to ensure the safe design, construction and operation of a dense phase CO2 pipeline. Failure frequency models are a major part of this QRA approach and the focus of this paper is a review of existing oil and gas pipeline third-party external interference failure frequency models to assess whether they could be applied to dense phase CO2 pipelines. It was found that the high design pressure requirement for a dense phase CO2 pipeline typically necessitates the use of high wall thickness linepipe in pipeline construction; and that the wall thickness of typical dense phase CO2 pipelines is beyond the known range of applicability for the pipeline failure equations used within existing failure frequency models. Furthermore, even though third party external interference failure frequency is not sensitive to the product that a pipeline transports, there is however a limitation to the application of existing UK fault databases with to onshore CO2 pipelines as there are currently no dense phase CO2 pipelines operating in the UK. Further work needs to be conducted to confirm the most appropriate approach for calculating failure frequency for dense phase CO2 pipelines, and it is recommended that a new failure frequency model suitable for dense phase CO2 pipelines is developed that can be readily updated to the latest version of the fault database. Document type: Article