numerical and analytical solution for natural gas production from methane hydrate dissociation
TRANSCRIPT
Numerical and analytical solution for natural gas production
from methane hydrate dissociation
By:
Behzad Hosseinzadeh
Introduction
Definition of the Natural Gas Hydrates
Where they can be found
Hydrate dissociation conditions
The problem of hydrate dissociation
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+
1m3
164m3
0.8m3
STP
Introduction
The problem of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
The problem of hydrate dissociation
hydrate dissociation → gasification of the drilling fluid → loweringof mud density → changes mud rheology → lowering hydrostaticpressure → further dissociation → wellbore enlargement andwellbore collapse
hydrate dissociation → change of mechanical and petrophysicalproperties of the sediment → increase in permeability →reduction in strength of the sediments
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Introduction
The problem of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
Some of the techniques adopted so far to avoid the risks of drilling in HBS
1. Cooling the drilling fluid
2. Increasing the mud weight
3. Adding chemical inhibitors and kinetic additives to the drilling fluid
4. Accelerating drilling by running casing immediately after hydrate areencountered and using a cement of high strength and low heat ofhydration
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
Production techniques
1. Thermal Injection
2. Inhibitors
3. Depressurisation
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
Review of Hydrate Reservoir Simulation Models
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
Santanu Khataniar
1. Hydrate dissociation occurs as soon as the reservoir pressure drops below the dissociation pressure for the hydrate at the reservoir pressure. The gas flows immediately to the free gas zone.
2. Hydrate decomposition is proportional to depressurization rate, and follows a first order kinetic model.
3. Rock and water expansion during gas production are negligible.
4. The model neglects heat transfer between reservoir and surroundings.
5. The reservoir is produced from a single well located at the center.
Analytical Model
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
Hydrate zone
Free gas zone
Analytical Model
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
for a closed system, the total volumetric change must be zero
using mass balance principles
GHi , GHr = initial and remaining gas in the form of hydrate, BgH = reservoir hydrate volumetric factor ,φ= reservoir porosity, SWi = initial water saturation , ∆hH = change in hydrate zone thickness, Gfi , Gp , GeH = initial free gas, total gas production and gas produced from hydrate ,Bgi , Bg = reservoir gas volumetric factor, Wp , WeH = total water production and water produced from hydrate dissociation, hg = gas zone thickness
After substitution , we have
Analytical Model
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
The volumes of initial free gas and initial gas in the form of hydrates (hydrated gas) in place are given by:
The ratio of initial free gas volume to initial hydrate volume is:
then
The water production rate is given by:
The pressure derivative respect to time isobtained from material balance equation
as:
Analytical Model
Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
This is done by using the approximation:
Z-factor is also pressure-dependent, and can be estimated using the Hall-Yarborough equation
Results of analytical
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
1. The gas hydrate in our assumed simulation is SI type, without the salt consideration;
2. Two-phase flow accords with Darcy’s law, and hydrate is stagnant in porous media;
3. The absolute permeability of porous media is the function of hydrate saturation;
4. The generated gas does not dissolve in water, and without hydrate reformation;
5. The diffusion and the dispersion are neglected in mass transportation;
6. There is no ice phase during the whole dissociation;
7. isothermal hydrate
8. the hydrate-bearing sediments are rigid and do not deform during hydrate dissociation.
Numerical Model
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
Model
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Infiltration equation Initial conditions
Supplemental formula
Auxiliary equation
Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
Results
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Introduction The problem
of hydrate dissociation
Some of the techniques
Production techniques
Review
Analytical Model
Results of analytical
Numerical Model
Results of numerical
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