Demulsification

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Demulsification
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OIL/WATER EMULSIONS IN PETROLEUM PRODUCTION

As water generally exists with oil in the reservoir, the oil is in most cases produced in the form of an oil/water emulsion.


During extraction, the shearing effect of flow in formations pores, pumps and completion restrictions leads to build up more or less stable emulsions.


Emulsion stability is increased by native or added surfactants: naphtenic acids, amine or sulphur derivatives, organo-metallic compounds, treatment chemicals (biocides, corrosion and scale inhibitors…)


Finely divided solids like iron sulfide, asphaltenes, paraffins, clays and silts could also participate to emulsion stabilisation. Those different products concentrate at oil and water interfaces and enable even low shear rate to fragment dispersed water droplets and form a more or less rigid film at the interface, preventing dispersed phase coalescence.

Electric charges of those elements create repulsive strength between droplets, leading to more stable emulsion.

Production

Producers are compelled to separate water from produced fluids for several reasons:

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  • Achieve refinery or customer specifications: Basic Sediment and Water (BSW) and salt content
  • Reduce production energy request by decreasing fluids viscosity
  • Reduce fluids volume to transport by early discharge of water
  • Reduce corrosion hazards

Driving mechanism of demulsifiers

In an emulsion, the speed of droplets settling depends on their radius, mass difference between the phases and viscosity (Stoke law)


Demulsifiers (emulsions breaker) act to increase water droplets radius and decrease viscosity.This is achieved by reducing the repulsive forces and interfacial tension, dewatering, neutralising zeta potential and reducing viscosity of interfacial film.

Demulsifiers design

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  • Due to diversity of oil and productions parameters demulsifiers must be designed specifically for each oilfield.
  • Aging of emulsions leads to changes in their characteristics.


For these reasons, demulsifiers must be formulated on site by bottle test method

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Formulated emulsion breaker comprise several different active substances carefully balanced.
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Scomi Anticor being an independent company, we use the best raw materials available on the market from selected sources without being bounded to procure from any upstream supplier.


Scomi Anticor's technicians are trained and experienced in bottle testing to design:

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  • The type and amount of non ionic surfactants for interfacial film destructuration
  • The type and amount of ionic surfactants for electric forces neutralisation
  • Final tuning of demulsifier, taking in account production specificities and other chemicals in the stream

On site deployment

Localization of injection point is also a key factor.


It must be located as upstream as possible, to allow longer contact time and shear of emulsion in the facilities. The resulting decrease of fluids viscosity reduces production costs and enable higher flow rate.

Proprietary chemicals

Scomi Anticor has patented chemicals for asphaltenes and paraffins treatments.   Those specifics products are very efficient to control hard to break emulsions generated by paraffinic or asphaltenic crudes.

Cases history of demulsification of stable emulsions

South Europe:

Oilfield was facing difficulties of production induced by very stable emulsion due to asphaltenes precipitated in the crude and accumulating at the oil/water interface.

The application of Anticor DSA 711 dual effect asphaltene dispersant / demulsifier is leading to fast separation with dry oil and clear water (SPE paper n° 30128)
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Northern Europe:

Gas field with condensates was producing water/condensate emulsions stabilised by asphaltenes. Design and application of a specific formulation Anticor DSA 801 BE has allowed the operator to control separation process at lower cost

Nigeria:

Oil production of acidic crude was requesting 150 to 200 ppm of acetic acid to obtain acceptable demulsification. Design of a specific demulsifier in cooperation between the producer and Scomi Anticor's technical staff resulted in suppression of acetic acid utilization.