Deep Sea Hydrate Flow Assurance Challenges - Forsiden · PDF fileParticle Size Analysis...

Center for Research on Hydrates & Other Solids, Colorado School of MinesCenter for Research on Hydrates & Other Solids, Colorado School of MinesCenter for Research on Hydrates & Other Solids, Colorado School of Mines

Deep Sea Hydrate Flow Assurance Challenges

Kelly Miller

Center for Research on Hydrates and Other SolidsColorado School of Mines

Norway - North America Petroleum Research WorkshopNovember 2, 2005


The CSM Hydrate Flow Assurance Team

John Boxall, Craig Taylor, Patrick Rensing, Joseph Nicholas, David Greaves, Simon Davies, Kelly Miller, Carolyn Koh, Dendy Sloan

Industrial CollaboratorsPatrick Matthews, Alberto Montessi, Ron Morgan,

Larry Talley, Douglas Turner, Zheng Gang Xu


Acknowledgements

DeepStar

CSM Hydrate Consortium

Additional Funding: NSF, DOE, NURP


Hydrate Flow Assurance Challenges

� Oil & Gas Production Moving to Harsher Conditions• Longer Flowlines• Transient Behavior: Shut-in and Restart• Traditional Hydrate Inhibition Impractical

� Need to Manage Hydrate Formation• Thermodynamics• Nucleation and Growth Kinetics• Aggregation and Flow Behavior• Hydrate Detection

� CSM Goal: Develop Tool to Predict Blockage Formation• If• Where• Approximately When


SimulationCSMHyK / OLGA 2000

Laboratory� Autoclave Cell� Particle Size Analysis� Rheometry� Micromechanical Testing� Calorimetry

Flow Loops• Texaco• ExxonMobil• University of Tulsa

CSM Hydrate Flow Assurance Approach


CSMHyK Hydrate Kinetics ModuleOLGA 2000: Industry Standard for Transient Multiphase Flow

fluid properties thermodynamic properties

system properties

growth rateamount of hydraterelative viscosity

CSMHyK Module

PipelineSection n-1

PipelineSection n

PipelineSection n+1

Yes

No DissociationModel

Hydrates?

FormationModel

ThermoProperties

RelativeViscosity

DrivingForce


Subcooling [K] �T=Teq-Top

0 1 2 3 4 5 6

Mol

es c

onsu

med

[mol/m

2 -sec]

0.0000

0.0001

0.0002

0.0003

278 K281 K284 KRegressed

Subcooling (K)

Met

hane

Con

sum

ed(m

ol /

m 2

s)Experimental Goal: Improve Model Assumptions

CSMHyK Assumptions

� Formation model• First order rate equation, proportional to:

� Subcooling� Water surface area

• Rate constant regressed from Bishnoi’smethane-water data

� Rheology model (Camargo & Palermo)• Hydrate aggregation in oil• 40 µm primary particles• Aggregates partially broken by shear• Aggregates flow as effective hard spheres


CSMHyK / OLGA 2000:Flow Loop Gas Consumption Predicted

600

700

800

900

1000

1100

1200

0 2 4 6 8 10 12 14 16 18 20Time (hr)

Pres

sure

(psi

a)

DataModel

Two fitting parameters:

� Subcooling atnucleation (matched toexperiment)

� Modified rate constantk = u kB

Petronius Oil in Texaco Flow Loop, 35 GPM Flow Rate


Industrial Use of OLGA/CSMHyK:Heat Transfer from Flow Line Limits Formation

30

40

50

60

70

80

90

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000Distance (m)

Tem

pera

ture

(F)

ambient T

hydrate formation T

10% water cut Alberto Montessi,Chevron

Understanding Hydrate Slurry Behavior is Key!


SimulationCSMHyK / OLGA 2000

Laboratory� Autoclave Cell� Particle Size Analysis� Rheometry� Micromechanical Testing� Calorimetry

Flow Loops• Texaco• ExxonMobil• University of Tulsa

CSM Hydrate Flow Assurance Approach


Conceptual Model forHydrate Plug Growth

Water

Oil

time, distance Hydrate Shells

WaterEntrainment

Hydrate ShellGrowth Agglomeration Plug

Gas


10-6

10-5

10-4

10-3

101 102 103 104

Conroe (Flow Loop)ConroePetroniusWest AfricanAlbacora Leste

Mea

n D

ropl

et D

iam

eter

(m)

��/� (m-1)

•

d �

��10/9

��1/2

�3/5

250

•

d = mean diameter� = shear rate� = oil viscosity� = oil/water interfacial tension

•

Water Entrainment: Droplet Size PredictableFrom Oil Properties, Shear


Hydrate Growth:Water Droplets Directly Convert to Hydrates

Particle Size Distribution Unchanged Upon Hydrate Formation


Hydrate Growth From Water Droplets

� Hydrates Grow as Shell onDroplet Surface

� Three Kinetic Limitations• Intrinsic crystal growth kinetics• Mass transfer through oil, hydrate• Heat transfer from hydrate

� Moving Toward Integrated ModelConsidering All Three Effects

Oil

Water

Hydrate Shell

Gas


100

101

102

103

100 101 102 103 104

34 vol%27 vol%22 vol%12.5 vol%10 vol%7.5 vol%5 vol%0 vol%

Visc

osity

(mPa

s)

Shear Rate (s-1)

Strongly Suggests Particle Aggregation

T = 4 oC

THF Hydrate/Oil Slurries:Shear Thinning, Yield Stress Fluids

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5Yi

eld

Stre

ss (P

a)Volume Fraction

T = 4 oC


0

5

10

15

20

25

30

35

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Hydrate volume fraction

�P

(psi

)

Anti-agglomerantsNo anti-agglomerants

Speed: 520 RPM (+)Gas Fraction: 46% (+)Water Cut: 35% (+)

Flow Loop: Aggregation Causes Large ?P

Need to Understand Agglomeration Under Real Conditions


Hydrate Flow Assurance:Research Challenges


Hydrate Plug Growth Research Challenges

Water

Oil


WaterEntrainment


Gas

Need to Understand and Quantify MechanismsNeed Real World Flow Line Data


Water Entrainment:Emulsion Formation and Stability

Water

Oil


WaterEntrainment


Gas


Emulsion Formation and Stability

� Hydrates Form at Water-Oil Interface� Emulsion Formation: Predictable Drop Size?

• Crude Oil Properties• Shear in Flow Lines

� Emulsion Property Quantification• Stability and Aging• Surface Properties of Water-in-Oil Emulsions• “Non-plugging” Brazilian Crude Oils

� High Water Cuts• End-of-Life Fields: Up to 90% Water


Hydrate Nucleation and Growth

Water

Oil


WaterEntrainment


Gas


Hydrate Nucleation and Growth

� Nucleation Mechanisms• Traditional Nucleation

� Induction subcooling: outrunning the hydrates• Particle Collision• Effect of Oil Chemistry

� Formation Rates and Mechanisms• Shell Growth• Interior Growth

� Kinetic Inhibitors• Nucleation Inhibition• Growth Inhibition


Hydrate Aggregation and Rheology

Water

Oil


WaterEntrainment


Gas


Hydrate Aggregation and Rheology

� Even Small Amounts of Hydrates Could Cause Plugs� Need to Understand and Quantify Complex Slurry

Mechanical Properties• Hydrate volume fraction• Hydrate microstructure

� Shells, particle size, particle roughness, aggregate fractaldimension

• Oil properties• Multiphase morphology

� Hydrates in oil, hydrates in water, hydrate slippage� Hydrate Adhesion Strength

• Hydrate-hydrate and hydrate-wall• Temperature dependence

� Anti-agglomerants


Hydrate Blockage Formation

Water

Oil


WaterEntrainment


Gas


Blockage Formation: What Is A Plug?

� Qualitative Descriptions• Slush-like, powder-like, dry hydrates, etc.• Pass/fail results for flow loop, wheel tests• Continuous behavior can masquerade as qualitative changes

� Need a Quantitative Answer for “What is a Plug?”• Multiphase problem• Complex fluid: hydrates, oil, gas, water, wax

� Answer Will Involve:• Mechanical properties of multiphase mixture

� Yield stress, viscosity, shear thinning behavior, etc.• Multiphase flow regime and fluid morphology• Flow line dimensions, driving pressure• “In pipeline x, a plug has a yield stress �, a viscosity �, and spans

the pipeline”


Cold Slurry Flow

Water

Oil


WaterEntrainment

Hydrate Seedingand Growth Hydrate Flow

Gas

Requires Understanding of Nucleation, Growth, Aggregation


Gas Dominated Systems

� Very Different Mechanisms from Oil Systems

� Need Basic Understanding of Mechanisms• What is the conceptual picture?• Hydrate formation in mist?• Hydrate formation on contact with wall?

� Field Data is Available


Conclusions

� CSM is developing CSMHyK, a hydratekinetics simulator integrated into OLGA2000

� Need to understand and quantify hydrateformation mechanisms• Emulsion formation and stability• Hydrate nucleation and growth• Hydrate aggregation and complex slurry rheology• Quantitative definition of pipeline blockage• Cold slurry flow• Gas dominated systems

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