Introduction to gas hydrates

Transcription

1 Introduction to gas hydrates Jarle Husebø, UNC NVC FVC

2 Overview Gas hydrates (what, why and where) Gas hydrates as a future resource Production technology Gas hydrate production history Major players Statoil s research strategy 2

3 Gas Hydrates: What? Natural gas hydrate is a clathrate, an inclusion compound, where gas molecules are suspended within a crystalline structure of water molecules. Natural gas hydrates are stable under high pressure and low temperatures. 3

4 Hydrate structures Structure I Methane, ethane, Carbon Dioxide Structure II Propane, iso-butane Structure H Methane + neohexane, Methane + cycloheptane 4

5 GHSZ GHOZ GHSZ Depth Depth Hydrate stability window Base Permafrost BGHZ BGHZ Temperature Temperature GHSZ: Gas Hydrate Stability Zone GHOZ: Gas Hydrate Occurrence Zone BGHZ: Base Gas Hydrate Zone 5

6 Est. CH 4 in hydrate (10 15 Sm 3 ) Gas Hydrates: Why? Most confident estimate USA energy consumption over 1000 years at current rate Conventional gas reserve 0, Year Sloan and Koh (2008) 6

7 Reservoir quality ~100,000 tcf gas (~2, GSm 3 ) (~1, boe) Gas-hydrate-bearing sands seem the most feasible initial targets for energy recovery 85-10,000 tcf gas ( GSm 3 ) ( boe) 1 2 Undeformed muds Arctic sands Marine sands Fractured muds Mounds 1 Hydrate in sands Gas hydrate resources housed in sand reservoirs Shallow conventional reservoirs 2 Canada Solid hydrate Japan Coarse-grained continental sand Pore-filling marine turbidite sand Vein-filling, nodules and massive seafloor mounds Low resource density/environmentally sensitive Korea India GoM 3 Modified from Boswell 2009 Vein-filling in clay Nodules in clay Massive sea floor mounds Modified from Johnson (2011) 3 The Background Disseminated gas hydrate in fine-grained marine sediments Large volumes Very low (1-3 %) resource density China Disseminated in mud 7

8 Gas Hydrates: Where? Modified from Hester and Brewer (2009) 8 Classificati on: Internal

9 Hydrates in the industry today Flow assurance 9

10 Production strategies for gas hydrates Pressure depletion Heating Direct exchange with more stable hydrate former (e.g. CO 2 ) (Fire in the ice, May 2011, DOE) 10

11 Depth/Pressure Pressure depletion Advantage No need to add energy Pressure support from hydrate dissociation Disadvantage Dissociation is endothermic and will cool down the system Vast amounts of water produced with the gas Removing hydrate from consolidated sediments may compromise structural integrity Temperature seafloor 11

12 Depth/Pressure Heating Advantage Heating will counteract the cooling during dissociation Disadvantage Need to add large amounts of energy to the system Vast amounts of water produced with the gas Removing hydrate from consolidated sediments may compromise structural integrity Temperature seafloor 12

13 Direct exchange with more stable hydrate former (e.g. CO 2 ) Depth/Pressure Advantage Temperature No dissociation of hydrate. Keeping structural integrity Carbon neutral production process seafloor Long term storage of CO 2 Disadvantage Needs permeability/connectivity to access the entire reservoir with CO 2 - injection The exchange process is based on liquid-solid diffusion and is inherently slow (there are ways to speed this up) 13

14 Hydrate timeline 1969 Messoyakha starts production 1971 Imperial oil discovers hydrates in Northern Canada. Mallik site 1998 First hydrate research well at Mallik site 1999 Japan: Drilled first offshore hydrate research well Korea: KIGAM initiate hydrate program 2001 Japan: MH21 was created. Ultimate goal to make offshore production from hydrates viable by Mallik: Three research wells drilled. 470 Sm 3 of gas produced by depressurization 2003 Alaska: Dedicated hydrate research well drilled 2004 Japan: MH21 phase wells drilled offshore to map the Nankai Trough Korea: BSR indicating hydrate in the Ulleung basin India: NGHP expedition. Four separate legs of drilling. One site showed 128m hydrate Alaska: BP drills hydrate research well China: First hydrate expedition. Three sites show hydrates Korea: First hydrate expedition. Three sites show hydrates 2008 Mallik: Second production test finished (initiated in 2006) Sm 3 of gas was produced over a six day period 2009 Japan: MH21 starts Phase 2 with goal of two offshore production tests 2010 Korea: Drilled 10 sites. 10 LWD and 2 wireline logging and vertical seismic profiling Alaska: ConocoPhillips CO 2 injection test (Ignik Sikumi). Japan: Drilled first offshore production well 2013 Japan: Offshore flow test 2014 Korea: Offshore production test 2015 Japan: Long term offshore production test Alaska: BP planning for production test (date uncertain)

15 Hydrate players and activity 15

16 Statoil s research strategy Increase research activity on hydrate as a resource using our extensive knowledge of hydrate as a production problem Evaluate possible longterm production test 16

17 Introduction to gas hydrates Jarle Husebø Senior Researcher Reservoir Technology Tel: