1. TPG 4140 NTNU Natural Gas Hydrate
Professor Jon Steinar Gudmundsson
Department of Petroleum Engineering and Applied Geophysics
Norwegian University of Science and Technology
Trondheim
October 22, 2013

2. Outline Flow assurance solids Cooling with distance in pipeline
Relevance of gas hydrates
Hydrate formers (smallest gas molecules)
Liquid water and water vapour
Gas molecules inside ice crystal cages
Dissociation pressure (equilibrium)
Antifreeze and Hammerschmidt’s equation
Ormen Lange and Melkøya (MEG use)
Glycol dehydration
Gas reserves?
Global warming?
Cold flow?

3. FLOW ASSURANCE CONCERNS

4. Flow Assurance
Flow assurance is a concept used to describe the phenomena of precipitation and deposition of solids (and multiphase flow, not discussed here) in flowlines and pipelines. Flow assurance offers technical solutions at reasonable costs without risk to installations, operators and the environment.
Precipitation is not the same as deposition…

5. Flow Assurance Solids Asphaltene (pressure changes)
Heavy, polar molecules, amorphous solid
Paraffin wax (pipeline cooling)
Normal paraffin C20 to C40
Gas hydrate (pipeline cooling)
Methane, ethane, propane and butane
Inorganic scale (fluid mixing…)
Carbonates and sulphates

6. Hydrocarbon Solids
A: Phase envelope, B: Gas hydrate, C: Paraffin wax, D: Asphaltene, E: Multiphase flow

7. Siljuberg 2012 (from Rønningsen 2006)

8. Cooling, Wellhead to Platform/Terminal

9. Temperature and Distance

10. Relevance of Natural Gas Hydrate
Deposits in oil and gas pipelines!!!
Gas kick in offshore drilling!!
Storage and transport of gas!
Cold flow in subsea pipelines?
Gas resource (big claims)??
Global warming (hyd. melting)???

11. Mary Boatman, unknown reference

12. Gas Hydrate Formers

13. Natural Gas Hydrate
Major obstacle to production of oil and gas through subsea pipelines (due to cooling). Blocks pipelines.
Form when liquid water (condensed out from moist reservoir gas) and natural gas are present at “wrong” side of equilibrium line (typically 20 C and 100 bara).
Water molecules are stabilized by small gas molecules such that hydrates form (physical process, not chemical reaction).
Antifreeze chemical used/injected to lower the T at which hydrates form (lower “freezing” point of hydrate).
Typically, 50 % antifreeze (in liquid phase) required to prevent hydrate formation. Expensive, very expensive.

14. Produced Fluids NCS

15. A: Gas reservoir,
B: Oil reservoir,
C: Aquifer,
D: Cap rock,
E: Sealing fault.
A/B: Gas-oil-contact.
B/C: Oil-water-contact.
Gas in A saturated with water vapour (condenses out at surface).
Oil formation B contains formation water (saline).

16. GPA (1998)

17. Water Vapour at 10 (Top), 20 Middle) and 30 (Bottom) MPa

18. Gas Molecules Trapped in Cages 12-sided, 14-sided and 16-sided polyhedra
Small non-polar molecules, methane, ethane, propane and butane form gas hydrate. Carbon dioxide, hydrogen sulphide and nitrogen also form hydrate.

19. Gas Inside Ice Crystal Cages
Skalle 2009
Carroll 2003

20. Structure II Gas Hydrate

21. Dissociation Pressure
Holder et al. 1988

22. Equilibrium & Flow Assurance
Cooling w. distance
Carroll 2003

23. Hydrate Equilibrium (Dissociation Pressure)

24. Dissociation Pressure Gas Hydrate
Lower line natural gas mixture; upper line with CO2 and N2

25. Christiansen 2012

27. Glykol %

28. Hammerschmidt’s Equation

29. Properties of Alcohols, Glycols and Water

30. Hydrate Equilibrium Midgard Field Gas
Lunde (2005): Design av flerfasesystemer for olje og gass, Tekna

31. Ormen Lange, Nyhamna

32. Ormen Lange til Nyhamna
Ormen Lange, 121 km, 70 MSm3/d gass, 445 tonn/d MEG (=5,2 kg/s)

33. Snøhvit til Melkøya
Snøhvit, 143 km, 20 MSm3/d gass, 125 tonn/d MEG (=1,5 kg/s)

35. Natural Gas Resource? Hydrate Zone Limited by Subsurface Temperature
Senger 2009

36. Krey et al. 2009

37. Global Warming & Gas Resource
William Dillon, USGS

39. Hedne (2012)

40. NTNU Cold Flow

41. SINTEF Cold Flow

42. SINTEF Cold Flow
Sintef 2010

43. Summary
Natural gas hydrate one of several flow assurance solids in oil and gas production
Cooling along a pipeline gives rise to conditions for hydrate formation (free water and condensed water vapour)
Methane, ethane, propane and butane plus carbon dioxide, hydrogen sulphide and nitrogen form hydrate
Small gas molecules form hydrate inside an ice crystal cage at typically 20 C and 100 bar pressure (subsea systems)
Antifreeze (commonly MEG) used to move equilibrium line to lower temperature such that hydrate does not form
Drying (dehydration) of natural gas by TEG used to meet transport and sales specifications
Gas hydrate may give problems in offshore drilling
Gas hydrate considered a potential gas resource?
Gas hydrate a potential contributor to global warming?

44. References
Aske, N. (2011): Wax Control, Guest Lecture, TPG 4035 Processing of Petroleum, Department of Petroleum Engineering and Applied Geophysics, NTNU, March 7, 27 pp.
Carroll, J.J. (2003): Natural Gas Hydrates: A Guide for Engineers, Gulf Professional Publishing, Elsevier Science, 270 pp.
Christiansen, H.E. (2012): Rate of Hydrate Inhibitor in Long Subsea Pipelines, M.Sc. Thesis, Department of Petroleum Engineering and Applied Geophysics, Norwegian University of Science and Technology, Trondheim, ix+107 pp.
Hedne, P. (2012): Subsea Processing and Transport of Hydrocarbons, Guest Lecture, TPG 4035 Processing of Petroleum, Department of Petroleum Engineering and Applied Geophysics, NTNU, January 30, 34 pp.
Holder, G.D., Zetts, S.P. and Pradhan, N., Phase Behavior in Systems Containing Clathrate Hydrates, Reviews in Chemical Engineering, Vol. 5, Issue 1-4, 1-70.
Krey, V. & 17 Others: (2009): Gas Hydrates: Entrance to a Methane Age or Climate Threat?, Environ. Res. Lett., Vol. 4.
Lunde (2005): Design of Multiphase Systems for Oil and Gas, TEKNA Conference.
Mienert, J. (2012): Signs of Instability, Nature, Vol. 490, October 25, 2 pp.
Rønningsen, H.P. (2006): Transportation of Waxy Crudes in Multiphase Pipelines, Presentation in TPG 4135 Processing of Petroleum, Department of Petroleum Engineering and Applied Geophysics, Norwegian University of Science and Technology, Trondheim, 52 pp.
Siljuberg, M.K. (2012): Modelling of Paraffin Wax in Oil Pipelines, M.Sc. Thesis, Department of Petroleum Engineering and Applied Geophysics, Norwegian University of Science and Technology, Trondheim, xi+68 pp.
Senger, K. (2009): First-Order Estimation of In-Place Natural Gas Resources at the Nyegga Gas Hydrate Prospect, Mid-Norwegian Margin, M.Sc. Thesis, Deparment of Geology, University of Tromsø, 211 pp.
Skalle, P. (2009): Pressure Control During Oil Well Drilling, BookBooN.com, 100 pp.