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![Page 1: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/1.jpg)
Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate
Distribution in Marine Sediments
Sayantan Chatterjee Walter G. Chapman, George J. Hirasaki
Rice University, Houston, Texas
April 26, 2011
Consortium on Processesin Porous Media
DE-FC26-06NT 42960Shared University Grid at Rice
NSF Grant EIA-0216467
![Page 2: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/2.jpg)
Samples from Cascadia margin, offshore OregonTorres et al., Earth Planet. Sci. Lett., (2004)
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Gas hydrates: “Ice that burns”
Courtesy: USGS
![Page 3: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/3.jpg)
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Motivation
Potential energy resource
Geohazard:Submarine slope failure
Global climate change
Needed – A fundamental understanding of the dynamics of gas hydrate systems
![Page 4: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/4.jpg)
Simulate gas hydrate and free gas accumulation in heterogeneous marine sediment over geologic time scales
Key features: CH4 phase equilibrium and solubility curves
Sedimentation and compaction Mass conservation: organic matter, sediment, CH4 and water
CH4 generation by in situ methanogenesis (biogenic)
CH4 advected up from deep external sources (thermogenic)
Water migration with dissolved gas (advection) and diffusion
Heterogeneity: High permeability conduits (e.g., vertical fracture systems, chimney structures, and sand layers)
Model overview
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![Page 5: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/5.jpg)
Hydrate dissociation due to burial below BHSZ
Organic Carbon Seafloor
Sediment flux
Lt
BHSZ
Free gas recycleback into HSZ
Methane solubility curve
Geological Timescale
Subsidence
Schematic of hydrate formation and burial
Bhatnagar et al., Am. J. Sci., (2007)5
Sediment flux Sediment flux
BHSZ
Subsidence Subsidence
Seafloor
External fluid flux
Fluid fluxSedimentation Hydrate layer
extending downwards
![Page 6: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/6.jpg)
Hydrate dissociation due to burial below BHSZ
Organic Carbon Seafloor
Sediment flux
Lt
BHSZ
Free gas recycleback into HSZ
Methane solubility curve
Hydrate layer extending downwards
Geological Timescale
Subsidence
Schematic of hydrate formation and burial
Bhatnagar et al., Am. J. Sci., (2007)6
Sediment flux Sediment flux
BHSZ
Subsidence Subsidence
Seafloor,
1 f sed t
m
U LPe
D
,2 f ext t
m
U LPe
D
![Page 7: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/7.jpg)
Key dimensionless groups and scaled variables Peclet numbers:
Pe1: Ratio of advective fluid flux (due to sedimentation and compaction) to methane diffusion
Pe2: Ratio of advective fluid flux (due to external sources) to methane diffusion
Damköhler number:
Da: Ratio of methanogenesis reaction rate to methane diffusion
Beta:
β: Normalized organic matter concentration deposited at the seafloor relative to 3-phase equilibrium CH4 concentration
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![Page 8: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/8.jpg)
1-D model: Effect of upward fluid flux
Bhatnagar et al., Am. J. Sci., (2007)
ParametersPe1 = 0.1Da = 0β = 0
Peak Sh = 6%
Peak Sg = 5%
Pe2 = -5
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![Page 9: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/9.jpg)
1-D model: Effect of upward fluid flux
Bhatnagar et al., Am. J. Sci., (2007)
Peak Sh = 21%
Peak Sg = 21%
Pe2 = -15
ParametersPe1 = 0.1Da = 0β = 0
Peak Sh = 6%
Peak Sg = 5%
Pe2 = -5
![Page 10: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/10.jpg)
2-D homogeneous model (validation with 1-D)
BHSZ Peak Sh = 20%
Peak Sg = 17%
Parameters
Pe1 = 0.1Pe2 = -15Da = 0β = 0Nsc = 104
N’tϕ = 1.485
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2-D homogeneous model (validation with 1-D)
BHSZ Peak Sh = 20%
Peak Sg = 17% Sg = 19%
Sh = 20%
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Net fluid flux Pe1 + Pe2 Average hydrate flux Pe1<Sh> Hydrate saturation <Sh>
Net fluid flux and steady state average hydrate saturation <Sh>
ParametersPe1 = 0.1
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kfrac = 100 kshale
Effect of a vertical fracture system
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Seafloor
2 Lt
2700 mbsl
BHSZ
![Page 14: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/14.jpg)
BHSZPeak Sh = 26%
Peak Sg = 29%
Vertical fracture system with in-situ methanogenesis
Seafloor
Parameters
Pe1 = 0.1Pe2 = 0Da = 10β = 6
![Page 15: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/15.jpg)
BHSZPeak Sh = 48%
Peak Sg = 42%
Vertical fracture system with deep methane sources
Seafloor
Parameters
Pe1 = 0.1Pe2 = -2Da = 10β = 6
![Page 16: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/16.jpg)
BHSZPeak Sh = 53%
Peak Sg = 40%
Effect of permeability anisotropy (kv < kh)
Seafloor
Parameters
Pe1 = 0.1Pe2 = -2Da = 10β = 6kv/kh = 10-2
![Page 17: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/17.jpg)
BHSZPeak Sh = 53%
Peak Sg = 40%
Effect of permeability anisotropy (kv < kh)
Seafloor
Parameters
Pe1 = 0.1Pe2 = -2Da = 10β = 6kv/kh = 10-2
![Page 18: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/18.jpg)
Local fluid flux and Pe1<Sh>
![Page 19: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/19.jpg)
Result summary – Immobile gas
26%
29%
ParametersPe1 = 0.1Pe2 = 0Da = 10β = 6
11%
14%
Biogenic source only
Homogeneous Sh and Sg in fracture
![Page 20: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/20.jpg)
Result summary – Immobile gas
26%
29%
42%
48%
ParametersPe1 = 0.1Pe2 = 0Da = 10β = 6
ParametersPe1 = 0.1Pe2 = -2Da = 10β = 6
11%
14%
17%
14%
Biogenic source only
Biogenic + external flux
Homogeneous Sh and Sg in fracture
Homogeneous Sh and Sg in fracture
![Page 21: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/21.jpg)
Effect of free gas migration into the GHSZ
Parameters
Pe1 = 0.1Pe2 = -2Da = 10β = 6Sgr = 5%
Seafloor
BHSZ
Time = 6.4 Myr
Peak Sg = 33%
Peak Sh = 59%
![Page 22: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/22.jpg)
Effect of free gas migration into the GHSZ
Parameters
Pe1 = 0.1Pe2 = -2Da = 10β = 6Sgr = 5%
Seafloor
BHSZ
Time = 19.2 Myr
Peak Sg = 62%
Peak Sh = 75%
![Page 23: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/23.jpg)
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ksand = 100 kshale
Effect of a dipping sand layer
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Seafloor
10 Lt
2700 mbslHigh permeability sand layer deposited between two shale sediments
BHSZ
![Page 24: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/24.jpg)
Seafloor
Peak Sg = 38%
Peak Sh = 59%
BHSZ
Preferential accumulation within high permeability dipping sand layers
![Page 25: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/25.jpg)
Conclusions
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Enhanced hydrate and free gas saturations occur within high permeability conduits (e.g., vertical fracture systems, chimney structures, and sand layers)
Enhanced hydrate and free gas saturation within high permeability conduits is related to increased, focused, localized, advective fluid flux (PeLocal)
PeLocal can be used to compute average hydrate saturation <Sh> similar to our 1-D correlation
![Page 26: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/26.jpg)
Questions
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Back up slides
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Constitutive relationshipsDarcy flux for water
Darcy flux for free gas
Phase saturations
Effective stress - porosity relationship
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2-D water mass balance
Dimensionless water mass balance
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2-D sediment mass balance
Dimensionless sediment mass balance
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2-D organic mass balance
Dimensionless organic carbon mass balance
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![Page 32: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/32.jpg)
Dimensionless methane mass balance
2-D methane mass balance
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Porosity reduction (compaction) Biogenic source of methane
Organic matter leaving the GHSZ is dependent on the ratio Pe1/Da
,1 Sedimentation
Reactionf sed
t
UPe
Da L
Reduced porosity
Porosity and normalized organic carbon profile
33
1
0.7
0.1
t
o
N
Bhatnagar et al., Am. J. Sci., (2007)
Normalized organic content α
![Page 34: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/34.jpg)
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1-D model: Dissolved CH4 concentration, gas hydrate and free gas saturation
34
Seafloor
Seafloor
Adapted from Bhatnagar et al., Am. J. Sci. (2007)
Peak Sh = 2%
Peak Sg = 1%
Pe2 = -2
![Page 35: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/35.jpg)
Net fluid flux Pe1 + Pe2 Average hydrate flux Pe1<Sh> Hydrate saturation <Sh>35
Net fluid flux and steady state average hydrate saturation <Sh>
35
Bhatnagar et al., Am. J. Sci., (2007)
Pe1<Sh>Cascadia Margin (Site 889)Fluid velocity ~ 1 mm/yrPe1 = 0.061<Sh> = 3%
Increasing external flux
ParametersPe1 = 0.1, β = 6Nsc = 104 (Hydrostatic)N’tϕ = 1.485, tfinal = 12.8 Myr
![Page 36: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/36.jpg)
1-D and 2-D model liquid flux comparison
0
1 1
lm
l lw m
c
c c
0
1
lm
l lw m
c
c c
1-D model 2-D model
Pe2 = -40
Pe2 = -20
36
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ksand = 100 kshale
Effect of a high permeability sand layer
37
Seafloor
916 mbsf
4.58 km
2700 mbsl
High permeability sand layer deposited between two shale sediments
kfrac = 100 kshale
BHSZ
![Page 38: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/38.jpg)
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ksand = 100 kshale
Combined effect of vertical fracture system and dipping sand layer
38
Seafloor
916 mbsf
4.58 km
2700 mbsl
BHSZ
kfrac = 100 kshale
High permeability sand layer deposited between two shale sediments
![Page 39: Effects of Lithologic Heterogeneity and Focused Fluid Flow on Gas Hydrate Distribution in Marine Sediments Sayantan Chatterjee Walter G. Chapman, George.](https://reader033.fdocuments.net/reader033/viewer/2022051614/551a3540550346cb358b51c3/html5/thumbnails/39.jpg)
BHSZ Peak Sh = 11%
Peak Sg = 13%
Parameters
Pe1 = 0.1Pe2 = 0Da = 10β = 6Nsc = 104
N’tϕ = 1.485