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The effect of heterogeneities in hydrate saturation on gas production from natural systems

Riley, David; Marin Moreno, Hector; Minshull, Tim A.. 2019 The effect of heterogeneities in hydrate saturation on gas production from natural systems. Journal of Petroleum Science and Engineering, 183. 106452. https://doi.org/10.1016/j.petrol.2019.106452

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Abstract/Summary

Understanding the rate and time evolution of gas release from natural gas hydrate systems is important when evaluating the potential of gas hydrate as a future energy source, or the impact of gas from hydrate on climate. The release of gas from hydrate is heavily influenced by a number of factors, many of which vary through the hydrate system. The fundamental heterogeneity of natural gas hydrate systems is often poorly represented in models. Here we simulate depressurisation-induced gas production from a single vertical well in 34 models with heterogeneous 2D distributions of hydrate that include layered, columnar or random configurations and comparable models with homogenous saturation distributions. We found that the temporal evolution of gas production rate follows a consistent trend for all models, but at any time the gas production rate across the models varied by up to ±35% in the first year of production, and by up to ±25% thereafter. The primary control on the gas production rate is the overall amount of hydrate in the system, but local variations in hydrate saturation cause significant fluctuations in the time evolution of production. These hydrate variations can cause changes in the gas flow path through the system and associated drops in gas production rate continuing for multiple years. Overall, our results suggest that small levels of heterogeneity in hydrate systems can cause variations in the gas production rate similar in scale to much larger variations in homogenous systems. Our work provides an error margin for previously modelled gas production rates, and a note of caution for potential commercial development of gas hydrate.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1016/j.petrol.2019.106452
ISSN: 09204105
Date made live: 02 Oct 2019 09:36 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/525273

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