O This paper is a part of the hereunder thematic dossier
`
`published in OGST Joumol, Vol. 67, No. 6, pp. 883-1039
`ond avoilable online here
`thématique ci-dessous
`Cet article fait partie du dossier
`publié dans la revue OGST, VoL 67, n°6, pp. 883-1039
`téléchargeable içi
`et
`
`la direction de : B. Bazin
`DOSSIER Edited by/Sous
`Challenges and New Approaches in EOR
`Défis et nouvelles approches en EOR
`Oil &GasScienceand7Fehnology-Rev.IFPEnergiesnouvelles,Vol.67(2012).No.6,pp.883-1039
`20\2.lFPEnergiesnouvelles
`Copyright
`
`to considerwhenstudying krylomide-8 sed
`Enhanced
`0/I RecoverY
`tensidèler
`vue de
`du pëlrole
`
`l'étude des
`lors
`de
`leur utiisation
`pour
`
`en
`
`teractéristiques
`clés
`à base d'acrylomide
`polymères
`rëtupëration
`assistëe
`chimique
`la
`A.Ilanes, N. Gaillard
`
`883 >
`
`Editorial
`
`887 > some Key Features
`Polymers
`for Chemical
`
`Quelques
`
`ò
`
`und
`
`C.
`
`Favera
`
`903 >
`
`tiydrophobico#yModified sulfonoted Polyocrylamides
`for102:
`lujadivity in
`between Assodative ßellavior
`Correlations
`arid
`flie Biluted
`
`Regime
`
`Polyocrylemides
`
`conélations
`
`entre
`
`le
`
`G.0upuis,
`
`0. Rousseau,
`
`sulfonés
`
`hydrophobes pour
`modifiés
`careciëre
`associatif
`et
`l'in|ectivité
`R. Tobary, M. Argillier
`
`and
`
`B.
`
`Grassi
`
`la
`
`RAN
`
`:
`
`en
`
`régime
`
`dilué
`
`921 > Rormal Stresses
`Viscoelosticity
`
`and
`
`laterface
`
`Contreintes
`
`normales
`
`la viscaélusticité
`
`sur
`
`la
`
`of
`
`Influence
`Displacement:
`Oil Recovery Elficiency
`on Enhanced
`et déplacement d'interfete : influente de
`l'efficalité de
`récupération
`ossisiée
`8. Herzhnil,
`
`1. Avendano,
`
`N. Ponnatti,
`
`P. ßuienu
`
`and
`
`P.
`
`Coussai
`
`963 >
`
`fension
`
`Interlocial
`of Added Surfactants
`the Dynomic
`Effect
`on
`Belmviour of Alkaline/Diluted Ileavy Crude Oil System
`le comportementdynamique
`tensioatlif s
`l'elout
`Effet
`sur
`akeline/brut dilue
`tension
`interfaciale
`système
`solution
`du
`8. Barin ned
`Langevin
`
`de
`
`de
`
`de
`
`la
`
`5. Trabeki,
`
`A. Hutin,
`
`J.-F. Argillier,
`
`C. Dalmorene,
`
`D.
`
`969 >
`
`Predidica
`
`ÑOdeling
`
`of Surfactants'
`Ï00/S.
`A ÑeView
`
`Properties
`
`using kultiscale Molecular
`
`tensioactifs
`propriétés
`Prédioion
`de
`des
`modelisation moiëtulaire: une revue
`8. Crelen,
`N. Pannatti
`(. Nieto-Draghi
`
`and
`
`l'aide
`
`à
`
`d'outils
`
`de
`
`983 > Modeling themico/E0R Processes:
`to Reservo¡r
`Scale
`Modélisation
`réservoir
`
`des
`
`procédés
`
`EOR
`
`Some
`
`Illustmtions
`
`from lab
`
`chimiques:
`
`du
`
`laboratoire au
`
`F. Douarche,
`
`D. Rousseau, B.eurs, R.Tabory,
`
`P.Mareau
`
`und M. Morvan
`
`EOR ino Meander ßelt:
`
`de
`
`dans
`
`une
`
`931 > Mechanical
`Degradation Dnset
`Ilydrosoluble Model Polymer
`
`o
`
`of Polyethylene0xide t/sed
`for Enhanced
`Oil Recovery
`
`as
`
`Seuil
`
`de
`
`dégradolion
`
`en
`
`récuperation
`
`solutions
`méconique
`de
`des hydrocarbules
`assistée
`
`A. Dupos,
`
`i. Meneut, LF. Argillier
`
`and
`
`I. Aubry
`
`de
`
`polymères
`
`utilisés
`
`i 019> Numerical
`Modeling of Thermal
`Model of Thermal
`an AMR-Based
`
`f02: Comprehensive
`Coupling
`Fluid
`Flow ond Geomechanics
`
`of
`
`999 > Analysis
`of Heavy Oil Recovery by Thermal
`From 6eologicolto Reservoir Modeling
`10 fétupér0lion d'IluÏ
`Anolyse
`Í00Tde
`e
`de meendre: du modèle
`barre
`de réservoir
`t.fremand 0.terat
`
`R.Dessumps,
`
`N.Guy,
`
`modélisation
`
`per protéllé fliermique
`géologique
`In
`
`il
`
`941 >
`
`Volumes
`
`of Preformed Particle Gelfor Water
`
`large
`Infecting
`Conformance
`ControÏ
`d'importants
`pour
`
`In|ection
`
`préformées)
`réservoirs
`
`les
`
`volumes
`
`de
`
`gel
`
`de
`
`contröle
`
`du
`
`baloyage
`
`type GPP (gel
`ò particules
`inlettion d'eau
`
`dans
`
`en
`
`le
`
`matures
`
`Baulun Bui, MingåenWei
`
`ond Yukang
`
`Liu
`
`953 > Axisymmetric Dminage
`Dreinege
`géométrie
`hydrophabes
`a deux
`
`en
`
`in Hydrophobit Porous Media Micromodels
`exisymétrique
`des milieux pereux
`dans
`dimensions
`
`A. Cuence,
`
`M. Chabert, M. Morvan
`
`and
`
`li. Bodiguel
`
`Madëlisation
`
`d'EOR thermique
`numérique
`d'écoulement thermique
`basé
`un modèle
`udoptativeet
`le géométonique
`6. Enchèry and C.Renard
`
`N. Guy,
`
`: couple
`
`e complet
`
`entre
`
`une Ëistrétisation
`
`sur
`
`1Û29> Evolution
`during
`
`of Seismic
`Velocities
`Ibermal Ñ0COvery
`
`Ÿf0COSS
`
`llemy Oil Sand Reservoirs
`
`in
`
`des
`
`vitesses
`
`cours
`
`Evolution
`bitumineux ou
`flouray,
`D.H. Dean,
`
`1.-F.
`
`sismiques
`
`dans
`
`les
`
`reserveirs
`
`des
`
`procédés
`
`de
`
`récupération
`
`de
`
`sables
`thermique
`
`N. Guy,
`
`A. Berosi,
`
`P. Delage and M.Muisguy
`
`SNF Holding Company et al v BASF Corporation,
`
`IPRP2a01e5-10
`
`g
`
`g
`
`60
`
`EXHIBIT
`
`

`
`Oil & Gas Science and Technology - Rev. IFP Energies nouvelles, Vol.67 (2012), No.6, pp.887-902
`Copyrigble20l3,1FPEnergiesnouvelles
`DOT: 10.2516/ogst2012065
`
`ChaÏfenges and New Approaches
`in EOR
`er nouvelles approches en EOR
`DéFis
`
`Some Key Features to Consider whenStudying
`Acrylamide-Based Polymers
`for Chemical Enhanced Oil Recovery
`
`A. Thomas, N. Gaillard and C. Favero
`
`SNF SAS, ZAC de Milieu×, 42263 Andrézieux Bouthéon - France
`e-maih olhomos@sof.fr - ogaillard@sal.Ïr
`- clavero@snf.fr
`
`à
`
`Résumé - Quelques caractéristiques clés à considérer
`lors de l'étude des polymères à base
`d'acrylamide en vue de leur utilisation pour la récupération assistée chimique du pétrole -
`Parmi
`l'injection de polymère est une technique
`les méthodes chimiques de récupération assistée du pétrolc,
`l'injection d'eau
`simple, connue de longue date et qui
`a démontré son efficacité.
`c principe repose sur
`le balayage et de diminuer le
`additionnée de polymore dans un réservoir pétrolier afin d'en améliorer
`contraste de mobilité entre cau et hydrocarbures grâce ò
`l'augmentation de viscosité. Cependant,
`la mise
`en œuvre d'une telle technique
`afin d'éviter
`toute dégradation
`un savoir-faire
`requiert
`spécifique
`potentielle du polymère, avec pour conséquence une chute de la viscosité de la solution injectéc.
`Le succës d'un projet d'injection de polymères commence avec
`la sélection du produit adapté aux
`la perméabilité ainsi que la
`du réservoir
`caractéristiques
`telles que la qualité d'eau,
`la température,
`l'oxygònc. Des études
`présence éventuc11e
`de contaminants
`comme le fer,
`l'hydrogène
`sulfuré et
`de
`stabi[ité menées
`long terme en laboratoire pennettent de s'assurer de la bonne tenue du produit
`tout au
`l'injectivité
`long de l'injection, tandis que des expériences d'injection sur carottes
`sont utiles pour vérifier
`le milieu porcux.
`la propagation de la solution de polymòre à
`travers
`et
`L'étape suivante concerne le design et
`la dissolution et
`la sélection des équipements qui vont servir
`l'injection de
`jouent un rôle primordial
`la solution dans le réservoir. Les installations de surface
`ce
`Ic but étant d'optimiser les étapes d'hydratation,
`de maturation et
`injection de
`la solution de
`stade,
`polymère en évitant
`toute dégradation,
`soit chimique (introduction
`d'oxygène),
`soit mécanique (duses,
`pompes centrifuges).
`important du projet
`dans l'eau de production est un autre aspect
`La dégradation du polymère présent
`d'injection. Plusieurs études ont montré qu'il n'y avait pas d'influence
`du polymère sur
`la séparation
`le polymère étant uniquement soluble dans l'eau.Une dégradation du
`entre le brul et
`l'eau de production,
`polymore résiduel préliminaire au passage des équipements de traitement d'eau peut être mise en œuvre
`afin d'abaisser la viscosité à 4 mPa.s et éviter
`toute difficulté dans Ic déroulement du processus.
`
`à
`
`d
`
`à
`
`à
`
`-
`
`-
`
`Some Key Features to Consider When Studying Acrylamide-Based Polymersfor Chemical
`Abstract
`Among Chemical Enhanced Oil Recovery (CEOR) methods, polymer
`Enhanced Oil Recovery
`It consists
`flooding is a straightforward
`technique with a long commercial history and proven results.
`in
`injecting polymer-augmented water
`into a subterranean formation in order
`to improve,
`thanks to the
`in the reservoir and provides a mobility control between water
`increase,
`the sweep efficiency
`viscosity
`implementingsuccessfrdly
`a polymer flood in the field requires specific
`and the hydrocarbons. However,
`know-how to avoid polymer degradation and associated viscosity
`loss.
`
`Page 2 of 17
`
`

`
`888
`
`Oil & Gas Science and Technology - Rev.1FP Energies nouvelles, Vol.67 (2012).No.6
`
`tire right polymerfor the reservoir, depending on the water
`The first stage begins with the selection of
`such as iron, hydrogen sulfide and
`quality, temperature, permeability and presence of contaminants
`tests have to be performed to ensure the long term stability of the product as
`oxygen. Several
`laboratory
`weU as core flooding experiments to check parameters sucli as injectivity and propagation through the
`porous medium.
`The next step is the design and selection of equipment for the dissolution and the injection of
`the polymer
`for the quality of
`the injected solution: the
`solution into the reservoir. Swfoce facilities are paramount
`to allow a good hydration, maturation and transport
`the solution while avoiding any type of
`goal
`of
`is
`can occur either chemically (oxygen ingress) or mechanically (chokes, centrifitgal
`degradation that
`plunps).
`the back-produced polymer. Several studies
`the degradation of
`Another aspect
`that can be assessed
`is
`the polymer
`the polymer on the separation of crude asul water;
`there is no influence of
`Irave shown that
`the produced water
`is above 4 mPa.s,
`being water-soluble. However, when the viscosity
`a treatment
`of
`may be operated before the water treatment process to avoid any dgiculty in the surface facilities and an
`optinuun eßiciency.
`
`INTRODUCTION
`
`An increasing number of oil
`fields has become mature and
`their production or
`has accordingly seen a decline of
`is on the
`point of doing so. The recovery
`these fields is
`rate of
`the oil
`currently about 15% to 35% on average of
`in place
`Hence, they still offer considerable production potential. The
`crude oil contained in the reservoirs is generally recovered in
`several
`steps.
`Production first
`the fluids
`results from the natural energy of
`and the rock decompression. Fonowing this depletion phase,
`of oil
`the quantity
`recovered at
`the surface represents on
`the initial
`It is
`some 5
`therefore
`average
`to 15% of
`reserve.
`in a second step,
`to employ techniques designed to
`necessary,
`the recovery yield while maintaining the pressure of
`boost
`the field.
`frequently used method consists in injecting
`The most
`through dedicated injection wells,
`water
`into the reservoir
`This is commonly referred to as secondary recovely. This
`second phase stops when the water content
`in the produced
`fluid is
`In terms of additional
`too high.
`recovery rate,
`the gain
`here is about 10-20%.
`The next usable techniques are combined under the name
`of Enhanced Oil Recovery (EOR). Their aim is
`to recover
`10 and 35% of additional oil. The term EOR
`between
`includes thermal
`techniques,
`non-thermal
`techniques such
`as electrical, miscible, steam or chemical
`techniques
`for
`the oil remaining in place (Willhite and
`enhanced recovery
`of
`Green, 1998).
`Among the
`possibilities, Chemical Enhanced Oil
`Recovery (CEOR), involving at
`the injection of water-
`least
`a dilute solution is
`a straight.
`soluble polymers in the form of
`long commercial history
`forward
`technique with a
`and
`in injecting polymer dissolved in
`proven results.
`It consists
`into a subterranean formation in order
`to improve,
`water
`to the viscosity increase,
`the sweep efficiency
`thanks
`in the
`reservoir and provide a mobility control between water and
`
`a viscous polymer solution
`the hydrocarbons. The injection of
`can be carried out alone or
`in combination with other chemical
`recovering additional oil. Among these
`compounds useful
`for
`other chemical compounds, mention can be made of
`the use of
`a weak, strong or extm-strong,
`inorganic or organic base capa-
`the crude oils and
`forming surfactant
`ble of saponifying
`species in situ for solubilizing the oil. By way of example,
`these include sodium carbonate,
`caustic soda, borate and
`metaborate compounds, silicates, metasilicates, amines, basic
`family of compounds commonly
`polymeric species. Another
`injected with polymers is based on surfactant compounds. The
`are mostly anionic and sometimes also zwitterionic,
`surfactants
`cationic and non-ionic. These compounds can be injected pure
`or along with a co-surfactant and/or a co-solvent
`to improve
`their compatibility and effectiveness
`in the reservoir.
`In all
`the propagation of
`these variations,
`the chemicals is
`improved by the addition of water-soluble
`polymers over
`injection alone, especially when it
`implemented
`water
`et al., 2010).
`field (Morel
`early in the life of
`Synthetic water-soluble
`polymers and in particular
`acry-
`lamide based polymers are the most common and advanta-
`increasing the viscosity
`of aqueous solutions and
`geous
`for
`are therefore widely used in EOR. Biopolymers can also be
`used for EOR but
`this paper will
`focus on synthetic polymers
`due to their industrial significance.
`The main polyacrylamides used
`are anionic in nature.
`studied and used for EOR,
`They have already been widely
`"Polymer",
`"Surfactant-Polymer",
`techniques
`called
`in
`"Alkali Surfactant Polymer" (P, SP, ASP) techniques.
`Many key aspects
`need to be considered for
`the design of
`a polymer
`reservoir characteristics
`(lithology,
`flood such as
`fractures), distribution of
`remaining oil, well
`stratigraphy,
`pauern and spacing, polymer degradation,
`rheology of polymer
`solution, compatibility with other chemicals, cost-effectiveness,
`intend to give a comprehensive
`etc. This paper does
`not
`overview of polymer flooding design but
`on several
`focuses
`
`is
`
`a
`
`Page 3 of 17
`
`

`
`A Thomas et al./ Some Key Features to Consider When Studying Acrylamide-Based Polymers
`for Chemical Enhanced Oil Recovery
`
`889
`
`important aspects that need to be taken
`field implementation.
`successful
`
`into account
`
`for
`
`a
`
`1 THE SELECTIONOF THE POLYMER
`
`1.1 Polymer Flooding: A Reminder
`
`The value of adding polymer to a conventional waterflood
`can be explained by considering the mobility ratio which is
`defined by the following formula:
`
`M -
`
`Ik,,
`- µ,,
`µ, /k"
`
`.
`where X , µ and k are the mobility, viscosity and effective
`permeability respectively and where the subscripts w and o
`to water and oil. Oil is
`left behind in a waterflood either
`refer
`(residual oil) or
`trapped by the capillary forces
`because
`it
`is
`1991). The mobility ratio
`because it
`is bypassed (Sorbie,
`improvement associated with the use of polymers minimizes
`the bypassing effect. Another parameter is the viscoelasticity
`associated with the use of high Molecular weight
`(Mw)
`or
`associative polymers. Some studies
`(Wang et al., 2000) tend
`to claim that
`the viscoelasticity may also contribute to
`recover additional entrapped oil compared to a conventional
`Newtonian fluid injection, but
`there is some
`controversy
`whether it applies to real
`reservoir conditions or not.
`can be divided in two
`Polymer-augmented waterflooding
`as described by Willhite and Green (1998).
`classifications,
`Firstly, when the mobility ratio during a waterflood is unfa-
`injection can increase the microscopic
`vorable, continuous
`in the reservoir. Secondly,
`even with a
`sweep efficiency
`favorable mobility ratio,
`the reservoir
`is heterogeneous,
`if
`can be implemented to
`polymer-augmented waterflooding
`reduce the water mobility in the high-permeability layers
`in
`order to recover the oil from the low-permeability
`layers.
`A typical polymer flood project
`involves mixing and
`injecting polymer over several months for surfactant slugs
`years for polymer alone at concentrations ranging
`and several
`from 300 to 3000 ppm, until 30% or more reservoir pore
`volumes have been affected.
`Reservoirs that are good candidates can be recognized by
`(Willhite and Green, 1998) and
`poor volumetric
`efficiency
`tolerance limits
`selected if the conditions respect
`the polymer
`(temperature, salinity). Thanks to the new developments
`in
`flooding can be implemented in higher
`chemistry, polymer
`salinity, higher temperature and lower permeability reservoirs.
`the boundaries that can be achieved
`At
`the laboratory scale,
`with new polymem (Vermolen et al., 2011; Kulawardana et al.,
`in Table 1. The success depends also on the
`2012) are given
`in place, as described by the permeability
`the oil
`viscosity
`of
`in the mobility ratio equation.
`factor
`
`a
`
`TABLE I
`Current limiis of some relevant parameters for polymer flooding
`implementation
`
`Reservoir temperature
`
`Reservoir permeability
`
`<13D*C
`
`> 40 mD
`
`Salinity
`oi! viscosity
`
`< 250 000 TDS (hardness dependent)
`
`2 mPa.s < µ < 10 000 mPa.s
`
`(SP) and Alkali-Surfactant
`1.2 Sudactant-Polymer
`Polymer Flooding (ASP)
`
`It is recognized that capillary forces
`cause large quantities of
`zones of waterflooded oil
`to be left behind in well-swept
`oil
`.
`reservoirs (Lake, 1989). Injecting surfactants (surface
`active
`.
`tension between oil and
`agents) can reduce the mterfacial
`water and therefore release trapped oil. Mobility control
`is
`by the injection of a polymer slug. However,
`it
`assured
`is
`of surfactants to bal-
`to inject costly
`dosages
`often necessary
`(0.5 to 1%). This effect
`ance the adsorption on rocks
`can be
`by adding alkalis to the solution. Alkalis, such as
`offset
`sodium carbonate, will adsorb on rocks
`(reducing surfactant
`increase the pH and generates in situ surfactants.
`adsorption),
`require expensive water treatment
`However, such process will
`facilities, and combined with the surfactant,
`can generate
`difficulties to break the produced emulsion. SP and ASP
`therefore be carefully designed and monitored.
`must
`New chemicals are currently being developed and studied
`the apparent viscosity of oil either by encapsula-
`to decrease
`tion or by thinning the micro-emulsion containing the oil.
`These new strategies have not been implemented in the field
`broaden the field of application of CEOR
`yct
`but may
`technologies in the forthcoming decades.
`
`1.3 Choosing the Right Polymer
`
`1.3.1 Properties of Polyacrylamide Polymers
`
`-
`
`-
`
`-
`
`flooding
`in polymer
`the polymers used
`The majority of
`applications is anionic acrylamide-based polymers and
`derived from:
`of acrylamide and sodium acrylate (or/
`copolymerization
`and sodium Acrylamido-Tertio-Butyl Sulfonate (ATBS));
`a polyacrylamide;
`cohydrolysis or post-hydrolysis
`of
`ter-polymerization of acrylamide
`copolymerization or
`or non-ionic functional monomers.
`ionic
`with other
`improve polymer thermal or salt
`Functional monomers
`of N-Vinyl
`tolerances (for example,
`incorporation
`improved thermal
`Pyrrolidone (NVP) for
`resistance).
`the repartition
`Depending on the manufacturing
`process,
`the polymer
`the anionic charges along the backbone chain of
`of
`physical properties when
`is changed and induces different
`
`Page 4 of 17
`
`

`
`890
`
`(cid:127)Acrylamide
`+ Water
`
`Oil & Gas Science and Technology- Rev IFP Energies nouvelles, Vol.67 (2012).No.6
`
`lusoluble
`Grairts
`of
`homopolymer of
`pofyacrylamide
`
`OO
`
`Q
`
`Granulation
`
`Polymerization
`T'C increases
`
`1
`
`- Acrylamide
`Sodium acrylate
`(cid:127) Water
`
`-
`
`-
`
`T*C
`
`incinases
`
`Grain
`
`of soluble
`
`Poly(acrylamum aaylate)
`
`copolymer
`
`wKh anionic
`
`charge
`
`randomly
`
`disitibu1ed
`
`NaOH dillusion
`the grain generales
`in
`diflerentiat
`hydre
`
`s
`
`32
`
`..I
`
`Granulation
`
`Drying
`
`and sieving
`
`copolymer
`01 soluble
`Pawder
`Poly(actylamide-co-sodium
`acrylate)
`for anionic
`with dilit
`composIllon
`charge
`
`r
`
`C
`
`g og
`
`gb3
`
`Sodium actylate
`
`Acrylamide
`
`Figure
`
`1
`
`Powderoi
`soluble
`Poly(acrylamide-co-sodlum
`*llit
`anlonic
`randomty
`
`copolymer
`acrylate)
`distribuled
`
`Sodium actylate
`Aclylamde
`
`( 4:*.a
`
`O
`
`Figure
`
`2
`
`Scheme of the post-ilydrolysis manufacturitig process.
`
`Scheme of tLie capolymerization
`
`process.
`
`TABLE2
`Range of products for several field conditiotts
`
`Form of product
`
`Type of polymer
`
`Monomer
`
`Example of product
`
`Copolymer
`
`Acrylamide - Sodium acrylate
`
`Flapaani 36305
`
`Powder
`
`Homopolymer
`
`post hydrolysed
`
`Acrylamide
`
`Copolymer
`
`Terpolymers
`
`Associative polymers
`
`Acrylantide - ATBS
`
`Acrylamide - Sodium
`Acrylate-ATBS
`Acrylantide- Sodium
`
`Flopaam6030S
`Flopaam ANI25SH
`
`Flopaam 5205SH
`Flopaamall5SH
`
`_
`
`Remarks
`T< 80°C medium hardness
`T<75°C low Itardness
`T<95°C all salinities
`
`.
`T<90°C all salinities
`
`Superpusher C319
`
`High resistance factor in
`
`reservoir
`
`Liquid O/W Emulsion
`
`Terpolymers
`
`Copolymers
`
`Acrylate - Hydroptiobic monomer
`Acrylamide-ATBS-NVP
`
`FlopaamSAV225
`
`Acrylamide - Sodiunt acrylate
`
`Flopaam EM533
`
`Medium hardness
`T<l20°Calisalittities
`T< 80°C medium hardness
`
`polyacrylamides are
`in water. Posthydrolysed
`dissolved
`a wide range of anionic chains (Fig. 1). Some
`composed of
`arc highly charged, others are less charged. The copolymeriza-
`tion of acrylamide and sodium acrylate leads to polymer with
`the anionic charges (Fig. 2).
`a more uniform repartition of
`These properties are very
`important
`the behaviour of
`for
`the
`polymers in aqueous solution especially
`the presence of
`in
`calcium and magnesium
`are also characLcrized by their
`Anionic
`polyacrylamides
`the molecular weight distribution (polydis-
`Mw as well
`as
`index: PDI). The range of Mw is between 4 and 30
`persity
`million g/mol and is determined using intrinsic viscosity
`measurement. PDI cannot
`be determined since neither
`standards with law PDI nor GPC (Gel Permeation
`Chromatography)
`technics exist
`today for
`such high Mw.
`like for
`However,
`the anionicity,
`a wide range of molecular
`weights is present
`in one product. Moreover, copolymers are
`more under control
`than post hydrolysed stmetures. Table 2
`
`products that can be
`some examples of manufacturing
`gives
`used in oilfields. Figures 3, 4 and 5 show some common
`polymer molecules.
`
`1.3.2 Properties of Polyacrylomide Polymers
`in Water Phase
`The thickening capability of anionic polyacrylamides is
`linked to the level
`of entanglement of
`the high molecular
`weight macromolecules and also lo the electrostatic repulsion
`between polymer coils and between segments in the same
`(Lake, 1989). When polyelectrolytes are dissolved in
`coil
`water containing electrolytes (salts),
`reduction in viscosity
`et al, 1995). This effect
`(Borthakur
`is auributed
`is observed
`leading to a reduction in
`to the shielding effect
`of
`the charges
`electrostatic repulsion and thus lo a
`less significant EXpanSiOn
`the polymer coils in the solution. The consequence is
`of
`volume and therefore a
`relatively lower hydrodynamic
`lower
`et al., 1980). Besides
`(Ellwanger
`the salt dependency,
`viscosity
`
`a
`
`a
`
`Page 5 of 17
`
`

`
`A Tlwmas et al./ Some Key Features to Consider When Studying Acrylonide-Based Polymers
`for Chemical Enhanced Oil Recovery
`
`891
`
`n
`
`_
`
`O
`
`NH,
`
`O¯
`
`m
`
`O
`
`Na
`
`Figure
`
`3
`
`of acrylamide and sodium acrylate (Flopaans
`Copolymer
`306305 type).
`
`molecular weight
`7). Moreover,
`the polymer
`(Fig.
`of
`in porous media for synthetic
`rheology
`polymers
`is quite
`different
`than in
`a viscometer
`topic is beyond the
`but
`this
`scope of
`this paper.
`the field, polyacrylamides have to be solubilized in
`In
`injection brine that contains dissolved salls. Total dissolution
`is achieved when no insoluble or swollen particles remain in
`filtration test. When high molecular weight (Mw> 1 million)
`(Mw around 18 million)
`or even very high molecular weight
`injectivity
`polymers
`are used,
`be observed.
`issues
`can
`sers are chemicar
`npartiall'ybsolu
`le
`
`co s-
`
`in
`
`e
`
`ch
`
`NH
`
`2
`
`Figure 4
`
`SOaNa
`
`Copolymer of acrylamide and ATBS (Flopaam ANI25 Lype).
`
`1 000
`
`Impact of shear
`
`rate on poly(acrylamide-co-acrylic
`Flopaam 36305
`
`acid)
`
`Bohlin Gemini. one-plate2*.
`/ = BS'C
`Brine
`3 360 TOS
`
`170 TDS Ca+Mg
`
`6
`
`cm
`
`740 TDS carbonate
`
`o
`
`N
`
`100
`
`Terpolymer of acrylamide, ATBS and NVP (Flopaani
`SAV225 typc).
`
`+
`
`-=-.
`
`1
`
`soeppm
`1000
`ppm
`
`-
`
`-
`
`+
`
`isoappm
`2000 ppm
`
`other factors
`influencing the viscosity of Partially Hydrolyzed
`(PHP) solutions are the degree of hydrolysis,
`Polyacrylamide
`struc¯
`solulion temperature, molecular weight,
`tri-dimensional
`ture and solvent quality (Sukpisan et aL, 1998).
`a polyelec-
`iso-molecular weight and iso-concentration,
`At
`trolyte is susceptible
`to have different conformations depending
`If compatible with the brine,
`on its chemistry.
`the molecule
`will uncoil, allowing inter-chain interactions. If not compatible
`with the brine, coiling will occur, resulting in intra-molecular
`associations. Other strategies have been developed to enable
`associations independently
`intermolecular
`from the molecu-
`lar weight of
`the polymer. The most advanced lechnology
`in incorporating hydrophobic moietics within a
`consists
`hydrophilic molecule. A concise overview of
`the technology
`and the chemistry for
`these so-called associative polymers is
`given by Wever et al. (2011).
`il
`fluids;
`as non-Newtonian
`Polyacrylamide
`fluids behave
`rate applied
`the viscosity depends on the shear
`means
`that
`(Fig. 6). They show a pseudo plastic (or shear
`thinning)
`behavior:
`decreases when shear
`viscosity
`increases-
`stress
`The viscosity
`is dependent upon the concentration
`and the
`
`Shear rate (s
`
`)
`
`Figure 6
`function of shear rate of FE3630S at different
`Viscosity as
`concentrationsal 6fC.
`
`a
`
`impact of concentration on viscosityon poly(acrylamide-co-acrylic
`acid)with different Mw. Flopaam3130 to3630S types
`Flopaam 31305
`sonin.onopswier,sem.
`
`-
`
`-
`
`45
`
`--
`
`Flopaam3430S
`
`29soros
`
`30
`
`-
`
`c
`
`e
`
`15 -
`
`j
`à
`$
`$
`
`1000
`
`y,
`Viscosity
`polymers.
`
`2000
`
`3000
`concentration (ppm)
`
`4000
`
`5000
`
`as
`
`a
`
`function of concentration
`
`of different Mw
`
`Page 6 of 17
`
`

`
`892
`
`Oil & Gas Science and Tecimology - Rev. IFP Energies nouvelles, Vol.67 (20 I 2), No.6
`
`amounts duc to the manufacturing process. When solubilized
`injected with
`in water,
`these species give micro gels that are
`the polymer in
`the formation. These micro gels
`can either
`propagate or damage the formation since they can plug pores
`to injectivity (increase
`the rock. Micro gels are detrimental
`of
`in injection pressure) and can block targeted areas.The areas
`that still contain oil arc no more accessible for
`further EOR
`a polymer
`therefore of
`importance
`techniques. For
`flood,
`it
`is
`to avoid accumulation of micro gels in the formation or make
`and soft enough to propagate deep in
`sure the gels are small
`the formation,
`Dissolution and viscosity depend on the chemistry of
`the
`polymer (manufacturing process, anionic
`content,
`of
`type
`anionic monomer).
`In Figures 8 and 9,
`it can be seen that
`post-hydrolyzed
`products FP 6030S is much
`tolerant
`less
`to
`calcium than polymer obtained by copolymerization
`process,
`regular HPAM (Partially Hydrolyzed
`FP 36305. Moreover,
`Polyaclylamide) polymers are known to suffer
`from modifi-
`cation with time if exposed to high temperature, which can
`Lead to incompatibility of
`the polymers Wilh the brine if diva-
`(Zaitoun and Potie, 1983). It is necessary
`ions are present
`Lent
`to change the chemistry to improve their stability. The poly-
`mers containing a sulfonated monomer ATBS are the best
`candidates for calcium tolerance, with an increased resistance
`for polymers with high ATBS content.
`.
`.
`Polyacrylamides
`are chemicals that can experience degra-
`.
`.
`dation. During the dissolution and injeclion processes
`three
`.
`main types of degradations can occur:
`chemical,
`thermal and
`.
`mechanical degradations, briefly described below.
`
`100
`
`g.
`
`10 -
`
`10
`
`a
`
`Effect of CaClg concentration
`of different polymers
`
`on viscosity
`range
`
`-
`
`,-
`
`-
`
`-
`
`-
`
`-
`
`-
`
`FP51155H
`AN125SH
`FP 36305
`FPSD30s
`
`PolymerconcentraIion:1500mm
`B cm, Espm, 25%
`2·,
`Bolilin, Cone pla1e
`geometry,
`Brine.10000TDS,noCa+Mg,nocamonale
`
`--
`
`- -------·---A------------(cid:127)
`
`.,
`
`-----
`
`-----
`
`........._
`
`Dilferences
`
`of vemsities
`
`are
`
`signifmanL
`
`O
`
`1
`
`i
`
`2
`
`3
`
`% caCl2
`
`>
`
`4
`
`I
`
`5
`
`6
`
`of different products,
`comprising a
`Ca[cium tolerance
`standard copolymer
`(FP 36305),
`a sulfanated copolymer
`terpolymers (FP 5205SH, FP Sil5SH) and a
`(AN 125SH).
`pos!-flydrolyzed polymer (FP6030S).
`
`the plateau as compared to initial viscosity
`
`Residual viscosity at
`50
`
`45 -
`
`92cos
`
`7.45eps
`
`assrange
`
`8.4
`
`Cps
`
`escos
`
`hydrolyzed
`
`40 -
`g35
`a 30 -
`i es
`
`.
`
`¯
`
`e-
`
`20
`
`15
`
`10
`
`5
`
`0
`
`-
`
`-
`
`O
`
`FP
`3630$
`Figure9
`
`FP
`6030S
`
`FP
`5205SH
`
`FP
`51155H
`
`AN
`1255H
`
`the plateau (Fig.
`Comparison
`the viscosity
`of
`at
`different polymers in the calcium lofemnce test.
`
`5)
`
`for
`
`1.4 The Main Types of Degradation
`
`a
`
`Few data exist on the quality of
`the produced fluid when
`using CEOR Lechniques. However,
`from internal
`reports and
`.
`.
`papers published by the Daqing and Shengli
`(Chma),
`fields
`.
`low viscosity of produced water
`frequently
`reported (Xie
`is
`and Liu, 2007). Typically, polymer concentration
`has been
`reduced by more than a half, anionicily has increased, and
`molecular weight
`five to ten times lower compared to what is
`injected. The arising question
`is whether
`this degradation
`occurs between surface and down hole or within the reservoir.
`In any case, preventing any of
`these degradations, would sig-
`.
`nificantly improve the control over
`the mobility ratio and
`consequently the amount of
`incremental oil
`recovered using
`POÍyCÌCCifOlyl€S.
`
`is
`
`lA.1 Chemical Degradation
`Chemical degradalion is ælated to the fonnation of
`free radicals
`that can reacL with the polymer backbone
`resulting in a
`(Grollman and Schnabel, 1982;
`drop of molecular weight
`Wellington, 1983) and a viscosity drop due to a
`reduclion of
`bydodynamic volume.Red/Ox systems
`are often involved in
`the generation of
`(Fenton, 1894). The presence of
`free radicals
`chemicals or
`impurities in the water, as well as oxygen, partic-
`in the formation of such radicals. For
`instance,
`Iron 11
`ipates
`and/or H2S in contact with oxygen contribute to the degrada-
`the polymers. Some commercial grade polymers
`tion of
`include systematically a minimal amount of stabilizers
`against
`the unavoidable occurrence of chemical degradation.
`Fine-tuning of
`the type of stabilizers and an merease of
`their
`respective dosages
`is also possible when chemical degradation
`is expected to be more significant.
`
`.
`
`.
`
`Page 7 of 17
`
`

`
`A Thomas et al./ Some Key Features
`to Consider When Studying Acrylamide-Based Polvmers
`for Chemical Enhanced Oil Recoverv
`
`893
`
`Viscosity as a
`
`function of shear stress
`
`concernraron
`(aenve):
`Petymer
`2',
`Bohltn. Cone plate geomelry,
`rale of 134 s '
`Shear
`Brine: 32265 TDS, 2265 TOS divalents
`
`1500 ppm
`6 cm,
`20
`
`c
`
`30
`
`25 -
`
`impact of shear rate on viscosity loss %
`on poly(acrylamide-co-acrylic
`acid)
`Flopaam 36305 - Flopaam 34305 - Flopaam 32305 types
`
`100
`
`-
`
`-n-
`
`-
`
`Flopaam 38305
`Flopaam 34305
`Flopaam3230S
`
`Polymerconcenitation:2000ppm
`rpm, 20°C
`Brooklieki,
`UL Spmdie,
`6
`Brine:25000
`TOS.
`and Mg,
`180 TDS Ca
`no carbonate
`I
`80000
`Shear rate (s¶
`
`I
`
`120000
`
`160000
`
`25 -
`
`0
`
`0
`
`1
`
`40000
`
`10 -
`
`,.
`
`5
`
`0
`
`-
`
`O
`
`-
`
`..
`
`'
`
`_
`
`111111
`50000
`100000 150000 200000 250000 300000 350000
`Shear stress (s
`
`1)
`
`Figure
`
`f0
`
`of mechanical degradation on a copolymer
`Impact
`(FP36305).
`a post-hydrolyzed
`polymer
`(FP 6030S) and
`recently developed salt
`tolerant polymers (Floc¤mb C3525
`and Flocumb C6225).
`
`1.4.2 Mechanical Degradation
`Mechanical degradation
`occurs in pipes,
`through chokes,
`above a certain velocity or pressure drop as
`valves
`or pumps
`as down hole through perfamtions.
`well
`the polymer is very
`The choice of
`important:
`the higher
`the molecular weight,
`the higher the sensitivity to mechanical
`degradation. Shearing a high molecular weight polymer
`can
`improve the injectivily of
`the solution inlo the reservoir with
`a minor viscosity
`loss. A drawback to this method can be the
`the viscoelastic effect which is mainly given
`loss of
`by the
`highest molecular weight
`the polymer
`fraction of
`(Wang ei «L,
`l show the impact of shear degrada,
`2001). Figures 10 and I
`tion on polymers with different molecular weights (Fig. 11)
`or according to two manufacturing
`(copolymeriza-
`processes
`(Fig. 10).
`tion for FP 3630S, post-hydrolysis
`for FP 6030$)
`The experiment was carried out with a pipe of 0.875 mm in
`length of 200 mm. As mentioned before,
`diameter and a
`the
`the higher the irreversible viscosity
`higher the molecular weight,
`loss.
`
`1.4.3 Thermal Degradation
`
`Thermal degradation depends on the type of polymer and the
`regulut HPAM polymers, an
`reservoir
`temperature.
`For
`increase in temperature will
`lead to an increase of
`the hydrolysis
`of acrylamide moieties (Fig. 12) generating a higher charge
`of anionic functionalities along the polymer backbone-
`density
`If the brine contains significant amounts of divalent cations
`such as calcium and magnesium,
`a viscosity drop is observed
`
`Figure 11
`copolymers with decreasing
`Impact of shear
`rate on ihree
`molecular weights:
`FP 3630S (high molecular weight)
`FP3430S (medium molecular weighl) and FP 3230$ (low
`molecular weight).
`
`CH2-CH
`
`o
`
`NHg
`
`Figure
`
`I.
`
`CH2-CH
`
`o
`ΠNH4+
`
`Hydrolysis of acrylamide moÍclies along the backbone chain.
`
`due to ionic bridges that can ultimately result
`in precipitation
`(Moradi-Araghi and Doe, 1987). Figure 13 shows that post-
`polymer (FP 6030S) precipitates
`hydrolyzed
`faster
`than
`in presence of calcium at 90°C
`copolymer (FP 3630$)
`their heterogencous charge distribution
`because of
`as
`explained earlier. The incorporation of sulphonated monomer
`to calcium (AN 125SH) at
`improves the Lolerance
`(ATBS)
`high temperature but
`the expense of
`in general at
`the molecu-
`cost. An optimal
`lar weight and with an
`increased polymer
`composition exists
`for each salinity and hardness and its
`determination requires laboratory studies,
`Taking into account the aforementioned parameters, it must
`be understood that
`is essential
`to fine-tune the structure,
`the
`it
`to optimize the resis-
`composition and the molecular weight
`a give