Numerical Simulation of Methane Hydrate in Sandstone Cores

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Numerical Simulation of Methane Hydrate in
Sandstone Cores
K. Nazridoust, G. Ahmadi and D.H.
SmithDepartment of Mechanical and Aeronautical
Engineering Clarkson University, Potsdam, NY
13699-5725National Energy Technology
LaboratoryU.S. Department of Energy, Morgantown,
WV 26507-0
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Gas Hydrates

• Ice-like Crystalline Substances Made Up of Two or
  More Components
• Host Component (Water) - Forms an Expanded
  Framework with Void Spaces
• Guest Component (Methane, Ethane, Propane,
  Butane, Carbon Dioxide, Hydrogen Sulfide) - Fill
  the Void Spaces
• Van der Waals Forces Hold the Lattice Together

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Energy Content
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Importance of Gas Hydrates

• Potential Energy Resources
• Potential Role in Climate Change
• Issues During Oil and Gas Production
• CO2 Sequestration

Objectives

• To Provide A Fundamental Understanding of Species
  Flow During Hydrate Dissociation
• To Assess the Reservoir Conditions During Hydrate
  Dissociation
• To Develop a Module for Simulation of Gas
  Hydrates Dissociation to be Incorporated in
  FLUENT Code

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Three-Phase Flow in Methane Hydrate Core,
Depressurization
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Hydrate Core
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Governing Equations
Continuity
Darcys Law
Saturation
Hydrate Dissociation - (Kim-Bishnoi, 1986)
Kinetic Model
Intrinsic Diss. Constant 124
kmol/Pa/s/m2, and Activation Energy ?E 78151
J/kmol
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Governing Equations
Energy Equation
Effective Thermal Conductivity
Hydrate Dissociation Heat Sink
Masuda, et al. (1999), c 56,599 J/mol, d
-16.744 J/mol.K.
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Governing Equations
Equilibrium Pressure
Makagon (1997), A 0.0342 K-1, B 0.0005 K-2, C
6.4804
Ambient Temperature
Outlet Press.
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Initial Conditions
Core Temperature (K) 275.45
Initial Pressure (MPa) 3.75
Initial Hydrate Saturation 0.443
Initial Water Saturation 0.351
Initial Gas Saturation 0.206
Initial Porosity 0.182
Initial Absolute Permeability (mD) 97.98
Boundary and Ambient Conditions
Ambient Temp. (K) Outlet Valve Pressure (MPa)
Case1 274.15 2.84
Case2 275.15 2.84
Case3 276.15 2.84
Case4 275.15 2.99
Case5 275.15 3.28
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Hydrate Core
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Tamb.275.15K
Simulation
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Tamb.275.15K
Simulation
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Temperature Comparison with Data
Ambient Temp. (K) Outlet Valve Pressure (MPa)
Case2 275.15 2.84
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Cumulative Gen./Diss. Comparison with Data
- Case (2)
Ambient Temp. (K) Outlet Valve Pressure (MPa)
Case2 275.15 2.84
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Five-spot Technique

• Four wells to form a square where steam or water
  is pumped in
• Gas is pushed out through the 5th well in the
  middle of the square

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Simulation
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Conclusions

• Depressurization method under favorable
  conditions is a feasible method for producing
  natural gas from hydrate.
• Gas generation rate is sensitive to physical and
  thermal conditions of the core sample, the heat
  supply from the environment, and the outlet valve
  pressure.
• Porosity and relative permeability are important
  factors affecting the hydrate dissociation and
  gas generation processes.
• For the core studied the temperature near the
  dissociation front decreases due to hydrate
  dissociation and then increases by thermal
  convection.
• Increasing the surrounding temperature increases
  the rate of gas and water production due to
  faster rate of hydrate dissociation.
• Decreasing the outlet valve pressure increases
  the rate of hydrate dissociation and therefore
  the rate of gas and water production increases.