Methane hydrates and sea floor processes and emissions Jrgen - PowerPoint PPT Presentation

Methane hydrates and sea floor processes and emissions Jürgen Mienert 30.October 2013

Wood and Jung, 2008 GLOBAL ASSESSMENTS

Global resource estimates decrease Global “Resource” Estimates - GIP

V Variety of Hydrate Forms in Nature Pore-filling in coarse grained sand Massive lenses and nodules in Disseminated in muds (China) (Canada) muds (India) 50,000 tcf 100,000 tcf 700,000 tcf 4,000,000 tcf Collett et al, 2008 Dallimore and Collett, 2005 Massive mounds on Sea-floor Thin veins in muds Pore-filling in fine-grained marine (Gulf of Mexico) (Korea) sands (Japan) Fujii et al, 2009 Park et al, 2005 Texas A&M and Scripps Institute

GH Energy Resource Assessment USGS (Collett et al., 2008) • Technically-Recoverables! • Discrete Accumulations – Used the USGS methodology that is used for “conventional” reservoirs – Three AUs; with size range and accumulations numbers for each • 85 tcf mean estimate – Existing Technology – High ultimate tech recoverability

Nankai Trough Fujii et al., 2008 Takano et al., 2007

Nankai Trough • Geologic GIP Assessment • A, H, Φ , S gh from log and seismic data • Area = 5,000 km 2 (10% of total prospective area) • 20 tcf in 10 high-S gh zones • 40 tcf in full section • % in sand- “anomalies” – Nankai Trough = 50% – Gulf of Mexico = 30% – Alaska N. Slope = 100% Saeki, et al., 2008

NW Svalbard • Vestnesa Ridge is a large sediment drift west of Svalbard. • Situated on relatively young Oceanic crust (< 20Ma). • Sediment thickness increases west to east, where it is about 6-8 km.

Vestnesa Ridge • Pockmarks at the top of the ridge. • Active venting system. • Faults at seafloor indicate recent tectonic activity. Hustoft et al., 2009

Vestnesa Ridge Hustoft et al., 2009 Hustoft et al., 2009

Active methane venting from the Vestnesa Ridge Smith et al., submitted . Gas bubble plumes above pockmarks at Vestnesa in 2010 and 2012

Bottom simulating reflector (BSR) indicates base of the gas hydrate stability zone

Vestnesa gas-hydrated ridge • BSR widespread covering an area of > 3000 km 2 . • Recognize 3 different BSR zones with differing controls (Vestnesa Ridge, continental slope, Molløy Transform, Knipovich Ridge). • Covers Vestnesa Ridge crest continuously. • Often absent at the foot of the Vestnesa Ridge. • Significant BSR occurrence at or across the Molloy Transform Fault. • BSRs north and south of the Vestnesa Ridge area.

Gas release at massive Hinlopen slide in the Arctic? Variable conditions in the area: • Geothermal gradient • GHSZ • Free gas area • Biogenic gas • Thermogenic gas • High Temperature