A Study of Analytical Solution for the Special Dissolution Rate Model of Rock Salt

By calculating the concentration distributions of rock salt solutions at the boundary layer, an ordinary differential equation for describing a special dissolution rate model of rock salt under the assumption of an instantaneous diffusion process was established to investigate the dissolution mechanism of rock salt under transient but stable conditions. The ordinary differential equation was then solved mathematically to give an analytical solution and related expressions for the dissolved radius and solution concentration. Thereafter, the analytical solution was fitted with transient dissolution test data of rock salt to provide the dissolution parameters at different flow rates, and the physical meaning of the analytical formula was also discussed. Finally, the influential factors of the analytical formula were investigated. There was approximately a linear relationship between the dissolution parameters and the flow rate. The effects of the dissolution area and initial volume of the solution on the dissolution rate equation of rock salt were computationally investigated. The results showed that the present analytical solution gives a good description of the dissolution mechanism of rock salt under some special conditions, which may provide a primary theoretical basis and an analytical way to investigate the dissolution characteristics of rock salt

Compositional variation of the Zechstein Group in the Norwegian North sea: Implications for underground storage in salt caverns

Halite beds in the upper Permian Zechstein Group represent an opportunity for the future development of underground storage caverns. However, geological factors such as lithological heterogeneities, cap rock characteristics and depth can affect the sealing capacity and the integrity of the cavern or contaminate the stored fluid. The main objective of this paper is to evaluate these factors focusing on the compositional variation of the Zechstein Group in different salt structures in the Norwegian North Sea, and related opportunities and challenges for salt cavern storage. Based on deformation style, geometry, height and thickness of the salt structures, we have divided the Zechstein Group into four main categories: (1) thin beds, which can be either carbonate-anhydrite or clastic dominated. Halite is absent and therefore there is no potential for the development of salt caverns. (2 and 3) bedded to weakly deformed evaporites and intermediate size salt structures, where thick halite beds of more than 300 m are present, but they are usually deeper than 2000 m. Lithological heterogeneities in the halite consist of a mix of competent and incompetent (K-Mg salts) lithologies. (4) Tall diapirs, characterized by shallower structures (<2000 m), with large deformation and poor seismic image. Thin layers of incompetent K-Mg salts are observed in these diapirs. The composition, thickness and deformation of the cap rock vary greatly in the area. Thick halite beds are recognized in most salt structures, suggesting an opportunity for underground storage. The challenges are related to the depth of the halite, amount and type of heterogeneities, characteristics of the cap rock and deformation in the different salt structures. These results also have implications for the distribution of reservoir and source rocks, and the evolution of the Northern Permian Basin.acceptedVersio

中国石油储备的补仓与释放策略及最优规模分析

石油安全是能源安全的核心部分,保障石油安全对于国家经济社会的长期稳定发展具有重要意义。石油储备作为保障石油安全的重要手段之一,能够有效地减轻国际原油断供所带来的负面影响,最终平抑石油价格、保障原油供应。充分发挥石油储备的作用需要明确影响储备补仓与释放的不确定因素,构建合理的补仓与释放策略,最终实现长期成本控制,同时还需要结合当前中国经济发展与能源供需的现实情况构建出最优的石油储备规模,保证石油储备能够发挥足够的应急作用。影响石油储备补仓和释放的主要因素包括价格、供给以及需求的不确定性。定量模型测算结果显示,我国石油储备的最优规模应当在117天左右,储备成本的下降、石油供应中断天数的上升以及石油价格的下降都倾向于最优石油储备规模的提升。结合敏感性分析的结果可以看出,石油最优储备规模对于石油供应中断天数最敏感,其次是储备成本,对石油价格则较不敏感。同时,根据对模型加入GDP收益前后的情况进行分析的结果显示,当考虑GDP收益时,石油储备规模必然会相应上升,而在这一前提下得出的石油储备规模适用于我国当前的主要发展状况,具有更强的现实意义。国家社会科学基金重点项目“绿色金融创新与政策保障研究”(17AZD013)振华石油控股有限公司项目(16701

Examining the systemic accident analysis research-practice gap

In order to enhance safety and prevent the recurrence of major accidents it is necessary to understand why they occur. This understanding is gained by utilising accident causation theory to explain why a certain combination of events, conditions and actions led to a given outcome: the process of accident analysis. At present, the systems approach to accident analysis is arguably the dominant research paradigm. Based on the concepts of systems theory, it views accidents as the result of unexpected and uncontrolled relationships between a system s components. Various researchers claim that use of the systems approach, via systemic accident analysis, provides a deeper understanding of accidents when compared with traditional theories. However, the systems approach and its analysis techniques are yet to be widely adopted by the practitioner community and, therefore, a research-practice gap exists. The implication of such a gap is that practitioners may be applying outdated accident causation theory and, consequently, producing ineffective safety recommendations. The aim of this thesis was to develop the current understanding of the systemic accident analysis research-practice gap by providing a description of the gap, considering its extent and examining issues associated with bridging it. Four studies were conducted to achieve this aim. The first study involved an evaluation of the systemic accident analysis literature and techniques, in order to understand how their characteristics could influence the research-practice gap. The findings of the study revealed that the systems approach is not presented in a consistent or clear manner within the research literature and that this may hinder its acceptance by practitioners. In addition, a number of issues were identified (e.g. model validation, analyst bias and limited usage guidance) which may influence the use of systemic analysis methods within industry. The examination of how the analysis activities of practitioners may contribute to the gap motivated Study 2. This study involved conducting semi-structured interviews with 42 safety professionals and various factors, which affect the awareness, adoption and usage of the systems approach and its analysis methods, were highlighted. The combined findings of Studies 1 and 2 demonstrate that the systemic accident analysis research-practice gap is multifaceted in nature. Study 3 investigated the extent of the gap by considering whether the most widely used analysis technique (the Swiss Cheese Model) can provide a systems approach to accident analysis. The analysis of a major rail accident was performed with a model based on the Swiss Cheese Model and two systemic analysis methods. The outputs and usage of the three analysis tools were compared and indicate that the Swiss Cheese Model does provide a means of conducting systemic accident analysis. Therefore, the extent of the research-practice gap may not be as considerable as some proponents of the systems approach suggest. The final study aimed to gain an insight into the application of a systemic accident analysis method by practitioners, in order to understand whether it meets their needs. Six trainee accident investigators took part in an accident investigation simulation and subsequently analysed the data collected during the exercise with the Systems Theoretic Accident Modelling and Processes model. The outputs of the participants analyses were studied along with the evaluation feedback they provided via a questionnaire and focus group. The main findings of the study indicate that the analysis technique does not currently meet the usability or graphical output requirements of practitioners and, unless these issues are addressed, will struggle to gain acceptance within industry. When considering the research findings as a whole a number of issues are highlighted. Firstly, given the benefits of adopting the systems approach, efforts to bridge the systemic accident analysis research-practice gap should be made. However, the systemic analysis methods may not be best suited to analyse every type of accident and, therefore, should be considered as one part of an investigator s analysis toolkit . Adapting the systemic analysis methods to meet the needs of practitioners and communicating the systems approach more effectively represent two options for bridging the gap. However, due to the multidimensional nature of the gap and the wide variety of individuals, organisations and industries that perform accident analysis, it seems likely that tailored solutions will be required. Furthermore, due to the differing needs of the research and practice communities, efforts to bridge the gap should focus on collaboration between the two communities rather than attempting to close the gap entirely