Assessing the impacts of commercial gas hydrate development

Abstract

Gas hydrate offers a large prospective reserve of unconventional natural gas. While research continues into possible production technology, investigation of the broader impacts of commercial development is needed to determine its future. I present the first attempt to comparatively analyse different commercial gas hydrate projects considering economic, social and environmental impacts, providing a foundation framework for future study. To this end, I develop a protocol using the ELECTRE multi-criteria decision analysis method for assessing between different gas hydrate exploitation projects. I define possible economic, social and environmental impacts to measure within this protocol, and suggest how each can be appraised by quantitative or qualitative decision criteria. These criteria are used, in collaboration with stakeholders, for structured comparative evaluation of development alternatives by means of an impact matrix. I construct criteria weights and decision thresholds from stakeholder input and use this information to calculate alternative rankings. Uncertainty remains in the effect of heterogeneity in petrophysical parameters on gas production, and this uncertainty is currently poorly represented in many production models. Gas hydrate saturation heterogeneity has been seen in natural systems, but it has not been modelled adequately for my protocol needs. I use TOUGH+Hydrate, a numerical thermo-hydraulic code for gas hydrate bearing geological systems, to provide a detailed quantification of gas production error margins resulting from heterogeneity in gas hydrate saturation. This modelling indicates that 10% saturation heterogeneity causes gas production fluctuations of ±25%, and 1% saturation variation in heterogeneous systems has equivalent impact to 10% saturation variation inhomogeneous systems. I test the complete protocol in Alaska to explore wider public perception of gas hydrate development, where I find society split into two groups, those prioritising resource production and economic returns from development, and those prioritising maximum benefit, or minimum damage, in the affected social and environmental systems. During fieldwork, the protocol proved accessible to a wide range of stakeholders across Alaskan society, satisfying the need for a broadly applicable tool. In all cases, Alaskan gas hydrate development is unsupported under current conditions due to the high economic, social and environmental costs of necessary infrastructure. Lastly I give examples of three further sites where the protocol may see use to illustrate the range of problems it has been designed for. For each site I suggest a series of qualitative and quantitative impact measures that may be used in future work and highlight a range of operational issues to consider. I use scenario analysis to explore the impact of varying the input parameters and ensure the protocol computes rational and justifiable results. Future protocol applications will benefit from wider collaboration throughout for better understanding of stakeholder priorities, especially with traditionally under-represented groups. Each of these case studies allows ultimate protocol refinement into a powerful and versatile tool, suitable for evaluating any gas hydrate production proposal. These studies show how an MCDA approach can be applied to gas hydrate development, providing a framework for future impact analysis.

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Identifiers

ORCID for David Christopher Riley: orcid.org/0000-0001-9829-004X

ORCID for Timothy Minshull: orcid.org/0000-0002-8202-1379

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