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E351A

by Jean-Louis Salager,Lab. Formulation, Interfaces, Rheology and ProcessesChemical Engineering School,University of the AndesMrida, Venezuela

A presentation for EniTecnologie, Milano-Italia, Oct. 2nd, 2002 2 / 60 E351A

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What is a Surfactant ?

SO3 Na+-

Dodecyl Benzene Sulfonate Sodium Salt

Lipophilic / Hydrophobic (non polar) Group

Hydrophilic Group(polar)

Usual representation

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12 25

O

OC H O S O Na

Dodecyl (ester) sulfateSodium Salt (foaming agent)

ANIONIC

CATIONICN

C H12 25

Cl -+

n-DodecylPyridinium Chloride

(desinfectant)

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pH 8C H

CH -CH -COO

12 25

2 2-

CH -N-CH3 3+

n-Dodecyl Betaine(cosmetic Soap)

AMPHOTERICor

ZWITTERIONIC

NONIONIC

H C3 OH C3 O

P-C HO

14 29

Dimethyl ether of TetradecylPhosphonic Acid (agro-emulsions)

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ADSORPTIONADSORPTION at interfaces ASSOCIATION ASSOCIATION in solution

ADSORPTIONADSORPTION ASSOCIATIONASSOCIATION

All Surfactants exhibit2 Fundamental Properties :

bactericideSome are

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ADSORPTION at interface

oil air

water water

water

NonpolarSolid

The Surfactant molecule adsorbsat interface to satisfy its dual affinity

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ADSORPTIONliquid-liquid interface

low tension emulsification capillarity speading adhesion instability

adsorption

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ADSORPTION solid-liquid interface

hydrophobation lubrication flotation wetting detergency

adsorption

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ADSORPTION Dispersions

= stabilization mechanisms foremulsions, suspensions and foams

electrostatic orsteric repulsion

drop, bubble, particle

drop, bubble, particle

Liquid Film

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ASSOCIATIONin solution

is spontaneous results in G < 0 reduces the contact between the solvent

and the solvent-hating group results in an organized structure:

normal or inverse micelle liquid crystal, microemulsion bilayer, membrane, vesicule, liposome

micelle

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Equilibrium between structures

sphericalmicelle

cylindricalmicellelamellar liquid crystal

surfactant in solution

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A Liquid Crystal is ... not a liquid ... nor a crystal

It is not stchiometric and can take up ...

water

oil solid

liquid

water

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Many Cases of Application Drilling Muds Acid Stimulation Injection control Asphaltenes control Enhanced Oil Recovery Crude Deshydration Emulsified Fuels Asphalt Emulsions etc ...

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Drilling Fluids should ...Cool and lubrificate the drilling bitTake away suspended cuttingsCounter-pressure & anti-filtration effects

mud

Bit

oilwater

cuttingclay

p

pp

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Drilling Fluids(water base)

water (cools, disolves and suspends things ) clays (viscosity, rheology) additives to increase density oil (lubrificates, facilitates drilling) surfactants (dispersants, emulsifiers) polymers (filtration control, rheology) etc ...

contain :

Lets see the role of some ingredients!

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Dispersing Agentsfor suspended solids

Should pull apart (clay) particles Should counter (clay and barite) flocculation Should provide plasticity and thixotropyLignin Derivatives, LignosulfonatesTanins (quebracho)Polyelectrolytes

reduce clay swelling emulsify

oilshelp controlling fluid losses

Ecological

Problems wi

th

Chromium sa

lts

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gasoils, residues, asphalts ... mono di-esters of vegetal oils from 5 to 15 % oil content

Other Surfactants(emulsifiers, foamers)

emulsify oils foaming and antifoaming agents corrosion inhibitors polymer activators

p

more

ecologi

cally

friendly

Oils22 / 60 E351A

Polymers(viscosity control)

polysacharides, polyacrylamides (pseudo) plastic rheology

special polymers associative, thermoassociative hydrophobically modified interactions with surfactants T

HIXOTRO

PY

PROBLEMS : biodegradation and thermodegradation

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Example of Surfactant-Polymer Interationanionic surfactant - polyethylene glycol

necklace type

100 EO unitsby SDS micelle

PEG

SDS Micelle

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Shear thinning RheologyVery fluid athigh shearin nozzle

newtonian fluid

plastic fluidbetter cleaning near wall !

reduces caking !

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Polymers(for filtration control)

natural polymer (xanthane, starch, gums) natural modified polymer (CMC, HEC) synthetic (part. hydrolized polyacrylamide) ... eventually + surfactants

1. Cover clay particles2. Link particles3. Gelify water

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Acid Stimulation a W/O emulsion is injected W = (HF+HCl) aqueous solution

Emulsion ofacid inaromatic gasoil

Porous medium

Sandgrain

attackacid

Gas oil

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Injection Problems due to Gravity Segregation

Steaminjection

Low oil saturation

High oilsaturation

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Foam Injectionto plug cracks and

high permeability zonesFoamingliquid

Pluggingfoam

Gasbubble

gaz

Porousrock

crack Sandgrain

Foam Plug

N2 gasorsteam

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Production of Petroleum + Water

Dehydration

Water must be separated (it is generally emulsified water)

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valve

tube,elbow

pump

defectivepump

gas

leak

incomingforeignsubstances

Emulsion formationrequires O + W + S

+ mixing

Where are W/OEmulsions formed ?

stirring - mixingin variouslocations

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Natural Surfactants ? Polyaromatic molecules as asphaltenes

NH N

HNNNi

N N

NNMg

CH2

H C3

CH

CO C H2 20 39

CH2CH3

CH2CH3

CH3

OCO CH2 3

H C3

H C2chlorophyll

Degradation,ion exchange

e. g. porphyrin structure

contains at leastone polar group

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Natural Surfactants ?

macromolecules (very) lipophilic flat ... cockroache piled up aggregates containing ... ... a few molecules

polar group

legs

= micelle= micelle

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Natural Surfactantsstabilize W/O emulsions

Waterdrop

PetroleumWaterdrop

Waterdrop

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Bottle testin practice

originalW/ Oemulsion

Add x ppmdehydrant

Homogenize

Pour inbottle

wait some time

Measure water separation

crude

water

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naturalsurfactant

efficientMixturedehydrantsurfactant

unstableemulsion

- SAD = 0 +corresponds to

Aspect of bottles (at variable formulation, concentration or dehydrant type)

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Orimulsion = Emulsified Fuel Heavy crude oil in water emulsion

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Emulsified Fuels O/W (or W/O)

the presence of water in a fuel-> reduces the burning temperature -> reduces corrosion and NOx formation-> increases gas density and Cp -> favors heat transfer -> reduces scale formation

pre-atomization makes combustion easier better control of oil spills available treatments (metals, sulfur, ashes)

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If 1/3 of this residual oil is producedultimate recovery is x 2

at 10 $/bbl benefit : 66 x x 10101212 $ $R&D incentive for EOR

Enhanced oil recovery

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First, only oil is produced

Then a oil + water mixture is produced, asituation that goes on with water flooding

Finally oil residual saturation is attained(Sor) and only water is produced

Capillary Trapping of Oil40 / 60 E351A

saturationOIL WATER

rela

tives

per

mea

bilit

ies

ko kw

2 Phase Flow

2 phases

Sor

Productionhistory

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WATEROIL

Pres

in

Cap

ilar

1 oil injectionrst

Waterinjection

oilinjection

2 phase motion in porous mediaimbibition and drainage

hysteresiscycle

Cap

illary

Pre

ssur

e

Saturation = memory

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advancing > receding

Contact Angle Hysteresis

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This complicates the motion problem

Because even in a cylindrical capillarya non-zero P is required to induce motion !

P = 0 P > 0

Without hysteresis With hysteresisadvancing > receding

Even worse if the capillary is not cylindrical

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Poiseuille P = v

Laplace P = 2 ( - )1R 1R 1 2

Hysteresis due to geometry

coniccapillary

LAPLACE Law :

P is curvedinterface

= 2 / R

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1

2

3

(1) when water is injectedit penetrates into thesmaller diameter pore(Laplace P)(2) then oil moves back intothe larger pore(3) and finally getsdisconnected from other oiland ends up trapped

oil

2 cylindrical capillarieswith different diameters

Hysteresis due to geometry46 / 60 E351A

Typical situation after waterflooding

disconnected Globulesresidual saturation 30 %

P Laplace >>> P Poiseuille

P Laplace = 2 / RP Poiseuille = v L

Capillary Number NCa v = = 10 -6

Mobilization requires a x 1000 increase

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Correlation NCa Recovery

NCa = v

Resi

dual

Sat

urat

ion

S or

10 - 4 10 - 210 - 6 10 - 4 10 - 210 - 6

Viscous forces

Capillary forces

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which alter capillary number Increase in v or Reduction in interfacial tension Wettability change

which alter saturations (phase volumes) Oil Swelling Oil Solubilization

others and combined mechanisms Miscibility (surfactant, CO2 sc) Emulsification (spontaneous or not)

Mobilization Mechanisms

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hydrocarbon-water = 1-10 mN/m hydrocarbon-surfactant solution 0.1 mN/m

near optimum formulation 0.001 mN/m

which alter capillary number bydecreasing tension (ultralow )

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ASP Process Engineering

1 injector 4 Producers

oil bank

injection in a 5-spot pattern

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General Principle Trapped oil is mobilized by something expensive ($$$)

which is injected as a narrow slug Mobilized oil moves forward and increases saturation

beyond Sor, Which results in an oil bank (2 phase flow) Everything is pushed by something viscous Which is in turn pushed something cheap (water)

$$$$

Sor

Sor

injec

tion

prod

uctio

n

saturation

drivewater

mobilitybuffer

oilbank

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At optimum formulation

Minimum Tension Easy Deformation Easy Emulsification

Low Viscosity Emulsion Very Unstable Emulsion

Can be different if formulation is off optimum as in thecase of pure alkaline flooding stable emulsion

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Asphaltenes Asphalt EmulsionsStructured Dispersions

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PROBLEM

Asphaltenes form colloids inapolar medium

slightly polarmacromoleculesthat are able to aggregate in micelles (stable colloid)

form deposits

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Colloids in apolar medium(asphaltenes)

Asphaltenic micelles can be stabilizedby resins (= surfactants or dispersants whichare even less polar than asphaltenes)

resinresin

asphalteneasphaltene

crude

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Asphalts are fluidized by solvent dilution heating emulsification

Asphalt Emulsionsfor road pavement

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Asphalt Emulsions

adsorption on rockadsorption on rock

ElectrostaticRepulsion

flocculation

hydrophobationhydrophobation

adhesionadhesion

Equilibria

1

2

2

3

3

4

breaking

4

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(acid) Corrosion Inhibition

waterH+ H+

Me Me Me

electrochemicalreaction =corrosion

adsorptionof H +

Me MeH2

Me++

adsorptionof cationicsurfactant

H+X

Me Me Me

protectionagainstcorrosionMe Me Me

hydrophobation

H S HS + H HS S + H2+ +- - - -

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Single layer structure in apolar medium results inWater in oil mini / microemulsion

waterdroplet

DIESELFUEL

100 - 1000 nm

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