A method to reveal workload weak-resilience-signals at a rail control post

Reorganization of a rail control post may affect its ability to cope with unexpected disruptions. The term ‘resilience’, the ability to manage spare adaptive capacity when unexpected events occur, encapsulates this situation. This paper focuses on the workload adaptive capacity through a method for revealing workload weak-resilience-signals (WRS). Three different workload measurements are adapted to identify structural changes in workload. The first, executed cognitive task load, targets system activities. The second, integrated workload scale, is a subjective measure. The last, heart rate variability, identifies physiological arousal because of workload. An experiment is designed to identify the workload change and distribution across group members during disruptions. A newly defined Stretch, the reaction of the system to an external cluster-event, is used to reveal a workload WRS. The method is suitable for real-time usage and provides the means for the rail signaler to influence the system through his subjective workload perception

CO2 sequestration in a UK North Sea analogue for geological carbon storage

The Fizzy discovery, a southern North Sea (UK) gas accumulation with ~50% natural CO<sub>2</sub> content, provides an opportunity to study the long-term quantity of CO2-related mineral reaction as an analogue for engineered CO<sub>2</sub> storage. The reservoir contains diagenetic dolomite typical of the formation; to identify and quantify any sequestration-related dolomite is challenging. To this end, CO<sub>2</sub> was extracted by stepwise extraction from dolomite from both the Fizzy discovery and equivalent sandstones from a low-CO<sub>2</sub> location. Between 0% and 22% of the dolomite in the Fizzy discovery precipitated due to the high CO<sub>2</sub> concentration. This corresponds to 11% ± 8% of the recent high-CO<sub>2</sub> charge sequestered as dolomite, a relatively low proportion after ~50 m.y. of potential CO<sub>2</sub>-water-rock interaction

Modelling carbon dioxide storage within closed structures in the UK Bunter Sandstone Formation

The Bunter Sandstone Formation in the UK Southern North Sea has the potential to become an important CO2 storage unit if carbon dioxide capture and storage becomes a widely deployed option for the mitigation of greenhouse gases. A detailed geological model of a region of the Bunter Sandstone consisting of four domed structural closures was created using existing seismic, well log and core data. Compositional simulation of CO2 injection was performed to estimate the storage capacity of domes within the system. The injection was constrained by both pressure and CO2 migration criteria, and the storage efficiencies of the domes (volume of stored CO2 divided by the pore volume of the dome) were calculated when injection ceased. A sensitivity study evaluated the effect of varying the total aquifer volume, reservoir heterogeneity and injection well location. A wide range of storage efficiency values were obtained across the different simulation cases, ranging from 4% (closed dome) to 33% (homogeneous model). Intra-reservoir heterogeneity, specifically in the form of continuous low permeability layers has an important effect on storage capacity in dome-like structures, because it increases the tendency for CO2 to migrate laterally from the storage complex via structural spill points

Geological storage of CO₂:Site appraisal and modeling

AbstractThe assessment of CO2 storage sites is similar in many ways to reservoir characterisation in the oil industry: An integrated team of geoscientists and engineers is required to collect and analyse data, generate models and perform flow simulations in order to make predictions. The main difference, in the case of storage in saline aquifers, is that there is usually less geological and petrophysical data available. It is therefore useful to know if storage assessments will be adversely affected by this lack of data.The CASSEM project (CO2 Aquifer Storage Site Evaluation and Monitoring), was initiated in 2008 to address this issue by studying two analogue storage sites in the UK. Although CO2 storage may not be undertaken at these sites, similar formations off-shore will likely be used for CO2 storage in the future. The two sites were modelled at three levels, proceeding from simple models based on little data to more complex models using more detailed geological data and simulating geomechanical and geochemical processes. The results of each level of modelling were compared in order to measure the effect of increasing model complexity.The conclusions from this work are that, in order to model CO2 storage accurately, a significant amount of geological information is required and that an integrated approach to reservoir characterisation for CO2 storage is very important. It is also very important to consider the geomechanical effects, both during the injection period and for several decades after injection has ceased