Numerical Simulation of Numerical Simulation of Methane Hydrate in Methane Hydrate in
Sandstone CoresSandstone Cores
K. Nazridoust, G. Ahmadi and D.H. Smith
Department of Mechanical and Aeronautical Engineering Clarkson University, Potsdam, NY 13699-5725
National Energy Technology LaboratoryU.S. Department of Energy, Morgantown, WV 26507-0
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
Gas Hydrates
A 1 m3 block of hydrate at normal temperature and pressure will release ~ 164 m3
of methane
Methane hydrate energy content of ~ 6855.90 MJ/m3
Methane gas – 42.0 MJ/m3
Liquefied natural gas 16,025.90 MJ/m3
Energy Content
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
Potential Energy Resources
Potential Role in Climate Change
Issues During Oil and Gas Production
CO2 Sequestration
Importance of Gas Hydrates
kk0kkk St
mu.
)w,gk(
Continuity:Continuity:
1SSS Hwg
pKK
uk
rkDk
Saturation:Saturation:
Darcy’s Law:Darcy’s Law:
Hydrate Dissociation - (Kim-Bishnoi, 1986) Kinetic Model:Hydrate Dissociation - (Kim-Bishnoi, 1986) Kinetic Model:
PTPSAMkm eH0HSgBg
RT
Eexpkk 0
dBIntrinsic Diss. Constant = 124 kmol/Pa/s/m2,
and Activation Energy ∆E = 78151 J/kmol
0dk
ePP
Governing Equations
)w,g,Hk(
Energy EquationEnergy Equation
Hg,Dggw,Dwweff
ggg0www0HHH0RR0
QuhuhTK
USUSTCSTC1t
Effective Thermal ConductivityEffective Thermal Conductivity
)KSKSKS(K)1(K wwggHH0R0eff
H
HH M
T.dcmQ
Masuda, et al. (1999), c = 56,599 J/mol, d = -16.744 J/mol.K.
Hydrate Dissociation Heat SinkHydrate Dissociation Heat Sink
Governing Equations
Governing Equations
Equilibrium PressureEquilibrium Pressure
C 273.15)-(T B 273.15)-(T A Plog 2e10
Makagon (1997), A = 0.0342 K-1, B = 0.0005 K-2, C = 6.4804
Ambient Temperature
Outlet Press.
Initial ConditionsCore 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
- Case (2)
Cumulative Gen./Diss.: Comparison with Data
Ambient Temp. (K) Outlet Valve Pressure (MPa)
Case2 275.15 2.84
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
Aquifer Zone
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.
Conclusions