Lection 7 Gas Hydrates in the Arctic Course

Lection 7 Gas Hydrates in the Arctic Course: Particularities and Features of Cold Region Geology by Alexey A. Krylov, Institute for Earth Science, St. Petersburg State University

GAS-HYDRATES: INTRODUCTION Importance Methane hydrate dissociation and methane emission : induces submarine slope failures makes a contribution to the global warming Arcti c What are gas hydrates? Crystalline solid consisting of gas molecules, usually methane, each surrounded by a cage of water molecules

GAS-HYDRATES: INTRODUCTION

GAS-HYDRATES: INTRODUCTION Gas-hydrates

GAS-HYDRATES: DISTRIBUTION Direct observations: more than 47 Gas Hydrate Accumulations (4 in the Arctic) Indirect evidences observations: 52 Gas Hydrate Accumulations

GAS-HYDRATES: MECHANISMS OF FORMATION Types of Gas-Hydrates accumulation Sea surface Fish Top of GHSZ Sea floor Near-surface gas-hydrates Deep-seated gas hydrate BSR-related gas-hydrate Gas-seep/gas vent/mud volcano Base of GHSZ Free gas BSR 1) Near-surface gas hydrates are being formed close to sediment-water boundary since P-T-solubility conditions here are most favorable 2) Deep-seated gas hydrates are usually related to sandy layers sealed with clay 3) BSR-related gas-hydrates are being formed at the base of GHSZ

GAS-HYDRATES: MECHANISMS OF FORMATION Bottom-simulating reflector - BSR

GAS-HYDRATES: MECHANISMS OF FORMATION GAS GENERATION IN THE SEDIMENTS AND SEDIMENTARY ROCKS

AMOUNT OF GAS IN THE GAS-HYDRATES Gas resources, trillion m 3 Gas hydrates (max estimation) Global Gas hydrates resources of natural (min gas estimation) Gas of deepwater areas

GAS HYDRATES IN THE WORLD OCEAN FLUID VENTING STRUCTURES 1) Mud volcanoes (shale diapirs) 2) Discharge of water-dissolved gas (cold seeps, water seeps, vents) 3) Flows of free gas (gas vents, gas seeps)

FLUID VENTING STRUCTURES IN THE OCEANS MUD VOLCANOES Worldwide distribution of onshore (1) and submarine (2 – without GH, 3 – GH bearing, 4 – inferred) mud volcanoes. 5 – “possible sediment diapirs” (Milkov, 2000)

FLUID VENTING STRUCTURES IN THE OCEANS: MUD VOLCANOES

FLUID VENTING STRUCTURES IN THE OCEANS MUD VOLCANOES Haakon Mosby mud volcano

FLUID VENTING STRUCTURES IN THE OCEANS MUD VOLCANOES The HMMV is approximately 1. 4 km in diameter, about 1. 2 km 2 in area, and has about 7– 15 m relief.

FLUID VENTING STRUCTURES IN THE OCEANS Discharge of water-dissolved gas

FLUID VENTING STRUCTURES IN THE OCEANS Flows of free gas Gas hydrates within gas venting sites are known in the following areas: in the Sakhalin slope of the Derugin Basin and near Paramushir Island in the Sea of Okhotsk; in the Gulf of Mexico; offshore Northern California.

FLUID VENTING STRUCTURES IN THE OCEANS The Flare-type anomalies on echo-sounder record

FLUID VENTING STRUCTURES IN THE OCEANS Sea of Okhotsk

FLUID VENTING STRUCTURES IN THE OCEANS Gas hydrate-bearing sediments Kitami Chaos

PROMISSING GH-BEARING AREAS IN THE WESTERN ARCTIC SHELF Eastern-Novaya Zemlya Trough Shtokman Area in the Barents Sea 0 temperature, C Sea level 0 -5 0 5 10 15 0 400 Глубина моря, м 200 Base of GHSZ 600 800 1000 200 400 Base of GHSZ 600 800 1000 1200 10 15 20 25 Ze ml ya Tr ou gh 5 No va ya ion ress Dep s rent a th B Sou ste rn 0 St. Anna Trough -5 Ea Water depth, m 20 1200

GH IN THE MESSOYAKHA AREA

GH IN THE CHUKCHI SEA GH (95% CH 4) GH (85% CH 4)

GH IN THE CHUKCHI SEA Last glacial maximum 100% CH 4 -bearing Gas Hydrates GH stability zone

GH AROUND SVALBARD Portnov et al. , 2016

GAS IN THE ARCTIC SHELF Hydrocarbon gases in shallow sediments based on coring results

PROMISSING GH-BEARING AREAS IN THE ANTARCTIC