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

Three-Phase Flow in Methane Hydrate Core,

Depressurization

Hydrate Core

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

Hydrate Core

0.375 cm 15 cm

22.5 cm

29.625 cm

Simulation Tamb.=275.15K

Simulation Tamb.=275.15K

Temperature: Comparison with Data

Ambient Temp. (K)

Outlet Valve Pressure (MPa)

Case2 275.15 2.84

- 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

Simulation

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