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SOLIDS DEPOSITION: AN OVERVIEW

Inorganic ScaleHydratesWax / ParaffinAsphaltenes

Month 2010Footer

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Content

Inorganic ScaleHydratesWax / ParaffinAsphaltenes

Topics: Types Causes Related problems Prevention Remediation

INORGANIC SCALE

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Inorganic Scale Types

Common types BaSO4, SrSO4 , CaSO4, CaCO3 , SrCO3

“Exotic” types FeS, ZnS, PbS, NaCl, CaF2, FeCO3, Ca3(PO4)2,

Silicates and NORM (Ra-226, Ra-228 and Pb-210)

Main types of scale BaSO4, SrSO4, CaCO3 and FeS (plus NORM)

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Inorganic Scale Causes

Causes of scale deposition depends on type: BaSO4 / SrSO4 → Water incompatibility (Seawater +

connate water) and process changes (T, P and pH) CaCO3 → Temperature increase and pressure

decrease FeS → corrosion or presence in the reservoir

BaSO4BaSO4

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Inorganic Scale Related Problems

Related problems Plugging and flow restrictions (near wellbore ,

tubing, wellhead, Separators, pipelines …) Emulsion stabilization (oil-wet solids) Suspended solids / damage to equipment

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Inorganic Scale Related Problems

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Inorganic Scale Prevention

Prevention: Chemicals (Scale Inhibitors) Removal of ions Drawdown management Physical inhibition (not conclusive) Metal surface treatment (coating and periodic

actuation)

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Inorganic Scale Remediation

Remediation: Chemicals ( Scale dissolvers = chelants) Acid Stimulation Mechanical removal (scrapers, brushers, pigs, jets and

mills)

HYDRATES

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Hydrate Types

Types:

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Hydrate Causes

Causes are the combination of: Low temperatures High Pressures Excess of water Hydrate agents (light hydrocarbons, H2S, CO2 and

N2)

Temperature

Pre

ssu

re Hydrate region

Hydrate free region

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Hydrate Problems

Problems: Plugging and flow restrictions (tubing, valves,

wellhead, risers, manifolds, jumpers, … ) Pipeline rupture Erratic pressure readings (oscillations)

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Hydrate Prevention

Prevention Chemicals (THIs, KHIs and AAs) Gas dehydration (e.g. glycol tower, molecular sieves

…) High temperature maintenance (e.g. insulation, burial,

external heaters, …)

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Hydrate Remediation

Remediation: Chemicals (THIs) Heat (e.g. Exothermal reactions) Depressurization

NH4Cl + NaNO2→ N2 + 2 H2O + NaCl + HEAT

MEG DEG

TEG

WAX/PARAFFINS

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Wax Types

Types: Straight Chain* Branched Chain Cyclic Chain

Wax definition= Paraffins with C16+

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Wax Causes

Main causes: Low temperature Low Pressure (Lost of light ends ) Crude with high content of C16+

Oil Characterization (GC-FID)

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Wax Related Problems

Problems: Plugging and flow restrictions (tubing, valves,

wellhead, risers, manifolds, jumpers, … ) Gelling and start up problems Increase of viscosity

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Wax Prevention

Prevention: Chemicals (Wax Dispersants and Inhibitors) Pipeline insulation, burial or heating Coating of metal surfaces High Shear flow

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Wax Remediation

Remediation: Chemicals (Wax Dispersants and Dissolvers) Heating (Exothermal reactions) Electrically heated pipelines Pigging, brushing and scratching Hot oiling

ASPHALTENES

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Asphaltene Causes

Causes: Mixture of different crudes Pressure changes

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Asphaltenes Related Problems

Problems: Plugging and flow restrictions (tubing, valves,

wellhead, risers, manifolds, jumpers, … ) Emulsion stabilization

Hypothesis - “Continental model”

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Asphaltenes Prevention

Prevention: Chemicals (Asphaltene Dispersants and Inhibitors) Minimize different fluid mixing Minimize pressure drops

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Asphaltenes Remediation

Remediation: Chemicals (Asphaltenes Dispersants and Dissolvers) Pigging, brushing and scratching

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