Difference between revisions of "Flow Assurance"
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==== Wax/Paraffin's ==== | ==== Wax/Paraffin's ==== | ||
[[File:Wax-Paraffin.png|300px]] | |||
* Wide range of high molecular weight paraffin's (alkalies or saturated hydrocarbons) | * Wide range of high molecular weight paraffin's (alkalies or saturated hydrocarbons) | ||
* Slightly soluble in oil | * Slightly soluble in oil | ||
* Solidify from oil primarily due to decrease in temperature | * Solidify from oil primarily due to decrease in temperature | ||
[[File:Wax-Paraffin Graph.png|right|450px]] | |||
* As wax solidifies from oil, there are three major concerns: | * As wax solidifies from oil, there are three major concerns: | ||
** '''Wax deposition''' on tubing or pipe walls during normal flow | ** '''Wax deposition''' on tubing or pipe walls during normal flow | ||
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*** During normal operation, low flow or turn down operation, or restart | *** During normal operation, low flow or turn down operation, or restart | ||
*** Note some high wax content oils tend to form stable emulsions | *** Note some high wax content oils tend to form stable emulsions | ||
[[File:Cloud Point.png|right|250px]] | |||
* Cloud Point or Wax Appearance Temperature | * Cloud Point or Wax Appearance Temperature | ||
** Temperature at which the first wax crystals form | ** Temperature at which the first wax crystals form | ||
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** As the temperature continues to drop more wax crystallizes | ** As the temperature continues to drop more wax crystallizes | ||
** Combine with thermal-hydraulic modeling to determine where wax can deposit | ** Combine with thermal-hydraulic modeling to determine where wax can deposit | ||
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[[File:Pour Point.png|250px]] | |||
* Pour Point | * Pour Point | ||
** Lowest temperature at which an oil can be poured under gravity | ** Lowest temperature at which an oil can be poured under gravity | ||
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** A yield force is required to break the gel and start the oil flowing | ** A yield force is required to break the gel and start the oil flowing | ||
** Defined by ASTM D97 test method | ** Defined by ASTM D97 test method | ||
[[File:Viscosity.png|right|250px]] | |||
* Viscosity | * Viscosity | ||
** An important parameter for sizing pipelines and pumps | ** An important parameter for sizing pipelines and pumps | ||
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** Above the cloud point the viscosity of oil only a function of temperature-Newtonian behavior. | ** Above the cloud point the viscosity of oil only a function of temperature-Newtonian behavior. | ||
** Below the cloud point, wax crystals suspended in the oil affect the viscosity, and viscosity is a function of temperature and shear rate-non-Newtonian behavior. | ** Below the cloud point, wax crystals suspended in the oil affect the viscosity, and viscosity is a function of temperature and shear rate-non-Newtonian behavior. | ||
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[[File:Wax Management.png|150px]] | |||
* Wax Management | * Wax Management | ||
** Mechanical | ** Mechanical | ||
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*** Operating procedures | *** Operating procedures | ||
==== Scale ==== | ==== Scale ==== | ||
[[File:Scale.png|300px]] | |||
* A deposit of inorganic mineral compounds from formation water | * A deposit of inorganic mineral compounds from formation water | ||
* Generally inorganic salts such as carbonates and sulfates of the metals calcium, strontium and barium | * Generally inorganic salts such as carbonates and sulfates of the metals calcium, strontium and barium | ||
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** Scale formation with sea water injection | ** Scale formation with sea water injection | ||
<!-- Enter the table here --> | <!-- Enter the table here --> | ||
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[[File:Scale Formation Table.png|right|200px]] | |||
* Scale can be managed by: | * Scale can be managed by: | ||
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** Allow scale to form and periodically remove it | ** Allow scale to form and periodically remove it | ||
*** Not practical for subsea developement | *** Not practical for subsea developement | ||
==== Asphaltenes ==== | ==== Asphaltenes ==== | ||
[[File:Asphaltenes.png|200px]] | |||
* What are Asphaltenes? | * What are Asphaltenes? | ||
[[File:What are Asphaltenes?.png|350px]] | |||
** Heavy, complex molecules | ** Heavy, complex molecules | ||
** Defined by solubility | ** Defined by solubility | ||
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** Do not have a single, unique structure or molecular weight | ** Do not have a single, unique structure or molecular weight | ||
** Do not melt | ** Do not melt | ||
[[File:Deposition.png|right|200px]] | |||
* Asphaltenes-Deposition | * Asphaltenes-Deposition | ||
** Asphaltenes can deposit due to a drop in pressure | ** Asphaltenes can deposit due to a drop in pressure | ||
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** Asphaltene deposits do not melt | ** Asphaltene deposits do not melt | ||
** Heat will not remove an asphaltene deposit or prevent asphaltenes from depositing | ** Heat will not remove an asphaltene deposit or prevent asphaltenes from depositing | ||
==== Calcium Naphthenates ==== | ==== Calcium Naphthenates ==== | ||
[[File:Calcium Naphthenates.png|300px]] | |||
* Naphthenates are solid that forms from a reaction between calcium in produced water and naphthenic acid in oil | * Naphthenates are solid that forms from a reaction between calcium in produced water and naphthenic acid in oil | ||
* Found in some West African and North Sea fields | * Found in some West African and North Sea fields | ||
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=== Internal Corrosion === | === Internal Corrosion === | ||
[[File:Internal Corrosion.png|right|300px]] | |||
* Corrosion can occur inside a pipe anytime water is present | * Corrosion can occur inside a pipe anytime water is present | ||
* Corrosion is accelerated by the presence of 0<sub>2</sub>, CO<sub>2</sub>, or H<sub>2</sub>S | * Corrosion is accelerated by the presence of 0<sub>2</sub>, CO<sub>2</sub>, or H<sub>2</sub>S | ||
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=== Emulsions === | === Emulsions === | ||
[[File:Emulsion.png|right|200px]] | |||
* Emulsions are complex mixtures of immiscible liquids consisting of a dispersed liquid in a continuous liquid phase | * Emulsions are complex mixtures of immiscible liquids consisting of a dispersed liquid in a continuous liquid phase | ||
* Water-in-oil emulsions | * Water-in-oil emulsions | ||
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* Viscosity | * Viscosity | ||
<!-- Insert "Viscosity" graph here --> | <!-- Insert "Viscosity" graph here --> | ||
[[File:Emulsion Viscosity.png|400px]] | |||
== Solids Management == | == Solids Management == | ||
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*** External or wet insulation-syntactic foams | *** External or wet insulation-syntactic foams | ||
* Insulation - flow line | * Insulation - flow line | ||
[[File:Insulation-Flowline.png|400px]] | |||
* Insulation - subsea manifold | * Insulation - subsea manifold | ||
[[File:Insulation-Subsea Manifold.png|400px]] | |||
* Active heating | * Active heating | ||
** Bundles | ** Bundles | ||
** Electrical flow line heating | ** Electrical flow line heating | ||
[[File:Active Heating.png|right|300px]] | |||
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== Chemical Injection == | == Chemical Injection == | ||
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** Umbilical and injection system design | ** Umbilical and injection system design | ||
** Operation monitoring | ** Operation monitoring | ||
[[File:Chemical Injection.png|300px]] | |||
== Operability == | == Operability == |
Latest revision as of 03:25, 3 October 2016
Flow Assurance
- Reservoir Fluids
- Sampling, lab fluid analysis, development of predictive reservoir fluid models
- Multiphase Flow
- Rheology, flow modeling – steady state and transient
- Pressure loss, diameter of tubing & flowlines
- Slugging and liquid surge
- Heat Transfer
- Insulation, heating
- Solids
- Hydrates, wax, asphaltenes, scale, etc.
- Flow restrictions or blockages
- Internal Corrosion
- Emulsions
- Sand
- Sand transport / deposition
- Erosion
- Production Chemistry
- System Operability
- Various operating modes: normal operation, shutdown, startup, well testing, turndown/rampup, pigging, etc.
Reservoir Fluids
- Fluid composition
- Gas
- Oil
- Water
- Reservoir "rock"
- Hydrocarbons
- Saturates/ Paraffins
- Aromatics
- Resins
- Asphaltenes
- Non-hydrocarbons
- Water
- Mineral salts
- CO2, H2S, mercaptans
- N2, He
- Metals
- Micro-organisms
- Saturation pressure (bubble point or dew point)
- Where does the density change?
- Switch from single to multiphase flow
- GOR
- How much does the density change?
- How much gas is with the oil?
- API gravity
- Measure of density
- Viscosity
- How does the fluid flow?
Multiphase Flow
- Multiphase flow is the simultaneous flow of multiple fluid phases (gas, oil, and water) inside a pipe.
- This flow can be in:
- Reservoir
- Wellbore
- Flowlines
- Risers
- Export pipline
- Flow Regimes
- Describe how the gas and liquid are distributed within a multiphase pipeline.
- Vertical Flow Regimes
- Horizontal flow map
Slip
- Under most conditions, the liquid, being more dense and viscous, moves more slowly than the gas
- Dispersed bubble and annular flow generally have little slip
- In downwardly inclined pipes, the liquid velocity can be greater than the gas velocity.
Holdup (HL)
- Relative amount of liquid at one point in a pipeline.
- Due to slip HL
Slugging
- Hydrodynamic
- Terrain
- Riser slugging
- Pigging
- Rate change
Solids
- Hydrates
- Wax/Paraffins
- Scale
- Asphaltenes
- Calcium Naphthenates
Hydrates
- Crystalline compounds of water and light hydrocarbon and other gas molecules
- Ice-like solid crystals
- Cages of water molecules surrounding hydrocarbon molecules
- Can form with methane, ethane, propane, isobutane, n-buttane, n2, CO2 and H2S
- Forms at temperatures higher than 32°F (up to ~80°F) at high pressure (> 50psia)
Hydrate prevention
- Chemical
- Thermodynamic inhibitors (shift chemical equilibrium)
- Methanol and other alcohols
- Glycols (MEG, DEG, TEG, others)
- Salt (brine)
- Low dosage hydrate inhibitors (a.k.a. LDHI)
- Anti-agglomerants
- Kinetic Inhibitors
- Thermal
- Maintain temperature above hydrate formation conditions
- Insulation
- Active heating
- Water removal
- Low pressure operation
- Maintain pressure below hydrate formation
- Thermodynamic inhibitors (shift chemical equilibrium)
- Blockage Remediation
- Remediation techniques are similar to prevention techniques
- Depressurization
- Most common method
- Chemical
- Thermal
- Depressurization
- Safety considerations
Wax/Paraffin's
- Wide range of high molecular weight paraffin's (alkalies or saturated hydrocarbons)
- Slightly soluble in oil
- Solidify from oil primarily due to decrease in temperature
- As wax solidifies from oil, there are three major concerns:
- Wax deposition on tubing or pipe walls during normal flow
- During normal operation
- Gelling of the oil during shutdown
- During shutdown and subsequent restart
- Primarily a dead oil problem
- Increases in viscosity due to wax particles suspended in the oil
- During normal operation, low flow or turn down operation, or restart
- Note some high wax content oils tend to form stable emulsions
- Wax deposition on tubing or pipe walls during normal flow
- Cloud Point or Wax Appearance Temperature
- Temperature at which the first wax crystals form
- At the cloud point, only a small fraction of wax molecules crystallize
- As the temperature continues to drop more wax crystallizes
- Combine with thermal-hydraulic modeling to determine where wax can deposit
- Pour Point
- Lowest temperature at which an oil can be poured under gravity
- Below the pour point, wax crystals form a matrix structure or a gel
- A yield force is required to break the gel and start the oil flowing
- Defined by ASTM D97 test method
- Viscosity
- An important parameter for sizing pipelines and pumps
- Is strongly dependent upon the temperature
- Above the cloud point the viscosity of oil only a function of temperature-Newtonian behavior.
- Below the cloud point, wax crystals suspended in the oil affect the viscosity, and viscosity is a function of temperature and shear rate-non-Newtonian behavior.
- Wax Management
- Mechanical
- Pigging
- Chemical
- Thermal
- Insulation
- Active heating
- Other
- Operating procedures
- Mechanical
Scale
- A deposit of inorganic mineral compounds from formation water
- Generally inorganic salts such as carbonates and sulfates of the metals calcium, strontium and barium
- May also be the complex salts of hydrous oxides and carbonates
- Scale formation and deposition occurs due to:
- Temperature and pressure changes
- Mixing of different waters
- Adding methanol or glycol to production stream
- Corrosion
- Deposition can occur in the:
- Formation
- Wellbore
- Flowlines
- Process Equipment
- Scale formation with sea water injection
- Scale can be managed by:
- Prevent deposition using chemical inhibitors
- Preferred approach for subsea
- May need to inject deep in the well
- May need to perform squeeze treatments in the formation
- Pre-treatment to remove scale formers in injection water (e.g. SRM - sulfate removal membranes)
- Allow scale to form and periodically remove it
- Not practical for subsea developement
- Prevent deposition using chemical inhibitors
Asphaltenes
- What are Asphaltenes?
- Heavy, complex molecules
- Defined by solubility
- ASTM D-3279-90
- Solid that precipitates when an excess of n-heptane or n-pentane is added to an oil
- Do not have a single, unique structure or molecular weight
- Do not melt
- Asphaltenes-Deposition
- Asphaltenes can deposit due to a drop in pressure
- Gas lifting can cause asphaltene deposition
- Asphaltenes can deposit due to the mixing of different oils
- Asphaltenes can deposit in the formation, well-bore tubing, flow-lines, and topsides
- Asphaltenes can cause emulsion problems
- Asphaltenes-Control
- Chemical
- Chemical inhibitors are available to prevent asphaltene deposition
- Mechanical
- Pigs can be used to periodically remove asphaltene deposits in flow-lines
- Must be combined with large quantity of aromatic solvent
- Chemical
- Asphaltenes-Remediation
- Asphaltene Solvents
- Asphaltenes are soluble in aromatic solvents (e.g. xylene, toluene)
- Used to remediate wellbores or other equipment
- May be used with coiled tubing
- Asphaltene Solvents
- Thermal methods
- Asphaltene deposits do not melt
- Heat will not remove an asphaltene deposit or prevent asphaltenes from depositing
Calcium Naphthenates
- Naphthenates are solid that forms from a reaction between calcium in produced water and naphthenic acid in oil
- Found in some West African and North Sea fields
- High TAN oils (TAN = total acid number)
Internal Corrosion
- Corrosion can occur inside a pipe anytime water is present
- Corrosion is accelerated by the presence of 02, CO2, or H2S
- Pipeline failures are a big potential liability
- Corrosion prevention
- Chemical inhibitors
- Protective coatings, corrosion resistant alloys
- Limit flow rates/velocities
- Other
Emulsions
- Emulsions are complex mixtures of immiscible liquids consisting of a dispersed liquid in a continuous liquid phase
- Water-in-oil emulsions
- Most common in crude oil systems
- Exists in water cuts as high as 80%
- Oil-in-water emulsions
- High water cuts
- Increased viscosity
- Separation
- Viscosity
Solids Management
- Thermal
- Insulation
- Active heating
- Chemical
- Inhibitors
- Disperants
- Coatings
- Mechanical
- Pigging
- Coiled tubing
Thermal Management
- Why are we interested in thermal management?
- Many of the potential solids are temperature sensitive, particularly hydrates and wax
- Viscosity increases (sometimes significantly) with decreasing temperature
- Thermal management options
- Insulation - keep the heat you have
- Active heating - add energy
- Insulation
- Flow lines
- External or wet insulation- syntactic foams
- Pipe-in-pipe
- Burial
- Bundle
- Subsea equipement
- External or wet insulation-syntactic foams
- Flow lines
- Insulation - flow line
- Insulation - subsea manifold
- Active heating
- Bundles
- Electrical flow line heating
Chemical Injection
- Chemicals are needed to control a number of potential solids and production chemistry concerns
- Chemical compatibility
- Chemical Injection- Design Philosophy
- Reservoir fluid analyses
- Chemical performance testing
- Umbilical and injection system design
- Operation monitoring
Operability
- Development of Operating Philosophies, Strategies, and eventually Procedures
- Integration of Flow Assurance Design
- Management of solids - chemical injection, insulation, etc.
- Deliverability, need for artificial lift
- Life of field assessment
- Definition of operating boundaries/ranges
- Consider various modes of operation
- Normal operation, well testing, shutdown, startup, etc.
- Operational monitoring
- Intervention requirements