Methane in Gas Shows from Boreholes in Epigenetic Permafrost of Siberian Arctic

Gleb Kraev,Alexander Kholodov,Elizaveta Rivkina,Anton Kudryavtsev,Tatiana Vishnivetskaya,Andrei Belonosov,Alexander Smirnov,Jacobus Van Huissteden,Dmitrii Zamolodchikov,Kanayim Teshebaeva

doi:10.3390/geosciences9020067

Abstract

The gas shows in the permafrost zone represent a hazard for exploration, form the surface features, and are improperly estimated in the global methane budget. They contain methane of either surficial or deep-Earth origin accumulated earlier in the form of gas or gas hydrates in lithological traps in permafrost. From these traps, it rises through conduits, which have tectonic origin or are associated with permafrost degradation. We report methane fluxes from 20-m to 30-m deep boreholes, which are the artificial conduits for gas from permafrost in Siberia. The dynamics of degassing the traps was studied using static chambers, and compared to the concentration of methane in permafrost as analyzed by the headspace method and gas chromatography. More than 53 g of CH4 could be released to the atmosphere at rates exceeding 9 g of CH4 m−2 s−1 from a trap in epigenetic permafrost disconnected from traditional geological sources over a period from a few hours to several days. The amount of methane released from a borehole exceeded the amount of the gas that was enclosed in large volumes of permafrost within a diameter up to 5 meters around the borehole. Such gas shows could be by mistake assumed as permanent gas seeps, which leads to the overestimation of the role of permafrost in global warming.

Highlights

The most recent estimation of the global methane budget includes the following listed sources of methane, in order of decreasing significance: the natural wetlands, geological sources, freshwater sources, hydrates, and permafrost [1]
Boreholes in West Siberia were located at the boggy watershed plain, poorly drained by tributaries of the Khadutta River, which is the left inflow of the Pur River
The gas shows from boreholes in epigenetic permafrost could be a strong source of methane, especially right after drilling

Summary

Introduction

The most recent estimation of the global methane budget includes the following listed sources of methane, in order of decreasing significance: the natural wetlands, geological sources (including oceans), freshwater sources (lakes and rivers), hydrates, and permafrost [1]. The thawing of permafrost provides a substrate and creates a favorable environment for the bacterial production of methane in wetlands and lakes [2]. It provides an input of methane to Geosciences 2019, 9, 67; doi:10.3390/geosciences9020067 www.mdpi.com/journal/geosciences. Geological sources globally emit about 54 (33-75) Tg CH4 yr−1 [1], which is four times less than natural wetlands.

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Results

Conclusion