Presented by J. L. Salager M. Rondón, J. C. Pereira, P. Bouriat, J. Lachaise, A. Graciaa

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1 1/54 8th International Conference on Petroleum Phase Behavior and Fouling, Pau June 10-14, 2007 Presented by J. L. Salager M. Rondón, J. C. Pereira, P. Bouriat, J. Lachaise, A. Graciaa

2 2/54 Emulsion breaking issues Formulation and optimum formulation Asphaltenes / demulsifier mixture Phenomenology of demulsifier action Quantifying variables effects Conclusions

3 3/54 Crude oil is generally produced as a water-in-oil emulsion Water is conate or injected Down-hole, water and crude are not emulsified (v = 1 ft/d) Emulsion generated during production by different factors Emulsion must be resolved to separate water.

4 4/54 5-spot array for waterflood Emulsion at ground level Two-phase flow at 1 ft/day No Emulsion down-hole = 1 cm/h

5 5/54 gas leak valve pipe, elbow pump Emulsion requires O + W + S + stirring Where do W/O emulsions generate? defective pump foreign chemicals stirring -mixing in various places

6 6/54 Reductions, valves, tees, elbows etc

7 7/54 Natural Surfactants? Asphaltenes, resins, acids, porphirins slightly polar molecules, often large ones (very) lipophilic somehow flat cookroach piled aggregates with a few molecules slightly polar group legs Form aggregates ± like inverse micelle

8 8/54 Where do they come from? For instance from polyaromatic molecules in protopetroleum CH 2 Pophyrin structure CH CH 3 polar group legs H C 3 H C 3 N N N Mg N CH 2 CH 3 CH 3 Degradation, ion exchange NH N Ni N HN CH 2 O H 2 C CO 2CH 3 CO 2C H chlorophyll Contains at least one polar group

9 9/54 Natural Surfactants stabilize W/O emulsions Water drop Water drop Water drop CRUDE

10 10/54 Slow Adsorption (10-20 h) water slow diffusion in crude (large molecules) self-interaction and self-aggregation at interface (lateral interactions) Bhardwaj A., Hartland S., Ind. Eng. Chem. Res., 33, 1271 (1994)

11 11/54 Strong Adsorption (Frumkin) but once they are tightly adsorbed they do not desorb (lateral interactions) CRUDE water

12 12/54 Emulsion breaking takes place stage by stage If one of the stage is slowed down or inhibited, the emulsion could turn very stable Becher P., Ed., Encyclopedia of Emulsion Technology, 4 volumes, M. Dekker ( ) Sjöblom J., Ed., Emulsions and Emulsion Stability, M. Dekker (2006)

13 13/54 3 Stages in Emulsion Breakup 1. Long distance approach 2. Thinning of interdrop film 3. Rapid coalescence after film rupture

14 14/54 Approach to short distance (0.1 µm) Settling in natural gravity field Stokes and Hadamard s laws Settling in artificial gravity or electrostatic field similar law [body force] Brownian motion kinetic energy ± 15 kt

15 15/54 Thin Film Drainage Various Phenomena Equilibrium Phenomena Electrostatic and Steric Repulsions Dynamic Phenomena Electrokinetic phenomena Hydrodynamics

16 16/54 Steric Repulsion (surfactants, particles, polymers) Adsorbed molecules (or particles) at interface repeal and oppose film drainage

17 17/54 Interfacial Viscosity Fluid drainage drags adsorbed molecules but lateral interactions oppose the motion

18 18/54 Most important (crucial) effect on emulsion stability is formulation influence! Takes place when drops are almost in contact

19 19/54 What is formulation? Formulation describes the physico-chemical interactions of the adsorbed surfactant with oil and water. oil (O) surfactant (C) Aco Winsor s R Ratio R = Aco Acw water (W) Acw R < 1, R = 1 or R > 1 related to phase behavior Winsor P., Solvent Properties of Amphiphilic Compounds, Butterworth London (1954)

20 20/54 Formulation Scan changes the phase behavior R < 1 R > 1 R = Aco Acw For instance if Formulation Variable = Salinity of aqueous phase Increasing salinity If salinity increases Acw decreases R increases transition R < 1 R = 1 R > 1 Bourrel M., Schechter R. S., Microemulsions and Related Systems, Dekker (1988)

21 21/54 Winsor s types of Phase Behavior W I W III W II Surfactant prefers water R < 1 R = 1 R > 1 Surfactant prefers a third phase (microemulsion) Surfactant prefers oil

22 22/54 W III Bicontinuous Microemulsion Structure at Optimum Formulation µem R = 1 Zero curvature like LLC microemulsion1

23 23/54 Bicontinuous Microemulsion Structure microemulsion2 Thermodynamically stable Lowest chemical potential structure (satisfies dual affinity and zero curvature) microemulsion3

24 24/54 Surfactant Affinity Difference direct measurement SAD = µ* - µ* = RT ln C /C w In three-phase behavior optimum formulation systems, excess phases do not contain micelles nor any structure. Appropriate situation to evaluate C O and C W at equilibrium (HPLC analysis) o o w Surfactant Partition Coefficient C O C W µem Marquez N. et al. Colloid Surfaces A, 100: 225 (1995); 131: 45 (1998)

25 25/54 Optimum Formulation SAD = 0 Correlations (first empirical, then based on SAD) ionic HLD = lns - K ACN - f(a) + σ -a T T = 0 Surfactant nonionic Salinity Oil Alcohol Temperature Surfactant HLD = α - EON + b S - k ACN - φ(a) + c T T = 0 Salager J. L. et al., Soc. Petroleum Eng. J., 19: 107 (1979) ANIONIC SYSTEMS Bourrel M. et al., J. Colloid Interface Science, 75: 451 (1980) NONIONIC SYSTEMS Antón R. E. et al., J. Dispersion Science Technology, 18: 539 (1997) CATIONIC SYSTEMS Hydrophilic-Lipophilic Deviation HLD = SAD / RT HLD = dimensionless SAD Salager et al., Langmuir, 16: 5534 (2000)

26 26/54 What happens at optimum formulation? Properties Interfacial Tension Conductivity (type) Emulsion Stability Emulsion Viscosity Drop Size γ κ O/W tc η ø Tension - SAD = 0 + conductivity W/O Stability Viscosity - SAD = SAD = SAD = 0 + Drop size - SAD = 0 + Formulation Scan

27 27/54 Why emulsions are unstable at optimum formulation? Various explanations! Surfactant is trapped in a microemulsion Surfactant forms liquid crystal bridges Holes in films are not stable (ultralow tension) Tension gradient tends to break the film Zero curvature is incompatible with formation of spherical drops Bourrel M. et al., J. Colloid Interface Sci., 72: 161 (1979) Salager J.L. et al., J. Colloid Interface Sci., 77: 288 (1980) Anton R. E. et al. J. Colloid Interface Sci., 111: 54 (1986) Hazlett R. D. et al. Colloids Surfaces, 29: 53 (1988) Kabalnov A. et al., Langmuir, 12: 8 y 12: 276 (1996) Ivanov I. et al., Colloids Surf. A, 128: 155 (1997)

28 28/54 Stability vs. Formulation Experimental Results (change of salt) HexadecylTriMethylAmmonium Bromide / Kerosen / Brine / 4 % n-pentanol Stability as log (time in sec for 60% coalescence) STAB STAB NaCl ZnCl 2 AlCl3 NaCl ZnCl 2 AlCl3 RT units Ln S (wt% Salt) Generalized Formulation (SAD) Same plot in SAD scale >>> allows comparisons

29 29/54 Stability vs. Formulation Experimental Results (different surfactants) 0.5 wt% Surfactant / Kerosen / Brine / 4 % n-pentanol HTAB Dodigen 266 Stability as log (time in sec for 60% coalescence) STAB RT units Generalized Formulation (SAD) Same plot in SAD scale >>> allows comparisons

30 30/54 Emulsion Stability vs. Formulation STABILITY O/W MOW 1/3 t c for Vc/V = 1/2 2/3 W/O phases 0 4 SALINITY (wt% NaCl) Salager et al., J. Dispersion Science & Technology, 3 : 279 (1982)

31 31/54 Stability vs. Formulation General Phenomenology t c W I WIII WII Stability deep minimum at optimum formulation O/W MOW W/O SAD

32 32/54 At the well head Lipophilic (natural) surfactant stabilizes a W/O emulsion. Stable W/O Emulsion Stability natural surfactants asphaltenes Hydrophilic - SAD = 0 + Lipophilic

33 33/54 Desestabilization requires to shift formulation to SAD = 0 natural surfactant is lipophilic demulsifier surfactant should be hydrophilic so that the mixture of both is balanced (SAD = 0). unstable emulsion demulsifier surfactant proper mixture natural surfactant asphaltenes - SAD = 0 +

34 34/54 Stability vs. Formulation Experimental Results (different cases) Stability (min) Salinity Scan EON Scan HLB Scan Stability (min) Salinity Scan EON Scan HLB Scan HLB, EON or Salinity (% NaCl) scale 0.1 O/W W/O HLD Stability varies more or less strongly close to SAD = 0 depending on the system

35 35/54 Accurate Formulation If resulting mixture formulation is slightly on one side or the other of optimum formulation (SAD = 0), emulsion could be stable! Mixing rule should be accurate! Optimum Formulation demulsification Salager J. L., Int. Chem. Eng., 30: 103 (1990) Krawczyk M., Wasan D. T., Ind. Eng. Chem. Res., 30: 367 (1991) Kim Y., Wasan D. T., Ind. Eng. Chem. Res., 35: 1141 (1996) Goldszal A., Bourrel M., Ind. Eng. Chem. Res., 39: 2746 (2000)

36 36/54 Assume linear mixing rule (as for HLB) Assume optimum formulation at HLB =10. Interfacial concentration and HLB of asphaltenes HLB M = x A HLB A + x D HLB D = 10 unknown but fixed demulsifier adjust not only HLB D but also concentration

37 37/54 2 degrees of freedoms HLB M = x A HLB A + x D HLB D = 10 Stability (min) Nonylphenol 15EO HLBD =??? W/O O/W HLB*d Demulsifier Concentration CD Interfacial concentration X D is related to bulk concentration and overall copncentration C D thru adsorption isotherm Stability (min) Demulsifier Conc. CD = 100ppm 100 W/O O/W 10 1 HLB*D HLBD (Nonylphenol polyeo series) Demulsifier Concentration CD Hence 2 D plot! CD Scan HLBD Scan Demulsifier EON (HLBD)

38 38/54 Add x ppm of demulsifier Pour in bottle Wait some time original W/ O emulsion Homogenize Measure water separation "Bottle test" in practice crude water

39 39/54 But mass transfer lag time could fade the results Other method: each surfactant is placed in the phase where it will be at equilibrium. Asphaltenes in crude Demulsifier in water After equilibration stirring Pour into bottle and watch settling

40 40/54 unstable emulsion demulsifier surfactant proper mixture natural surfactant asphaltenes - SAD = 0 + Aspect of test bottles (changing formulación, type or concentration of demulsifier)

41 41/54 2 types of scan: demulsifier concentration at constant type demulsifier hydrophilicity at constant concentration HLB M = x A HLB A + x D HLB D = 10 Stability (min) Nonylphenol 15EO HLBD =??? W/O O/W HLB*d Demulsifier Concentration CD Interfacial concentration X D is related to bulk concentration and overall concentration C D thru adsorption isotherm Stability (min) Demulsifier Conc. CD = 100ppm 100 W/O O/W 10 1 HLB*D HLBD (Nonylphenol polyeo series) Demulsifier Concentration CD CD Scan HLBD Scan Demulsifier EON (HLBD) Hence 2 D plot!

42/54 2 D Stability map Stability (min) C D scans at cst HLB D 1000 100 10 20 1 15 4.75 10 5.

42 42/54 2 D Stability map Stability (min) C D scans at cst HLB D C D Demulsifier Concentration CD (ppm) O/W Stability (as time for 50% water separation) < 1 min 1-20 min min min min >200 min Demulsifier EON Demulsifier Concentration CD 10 Nonylphenol EON W/O HLB ,75 5, HLB D

43 43/54 Same with two different demulsifier families More hydrophilic the demulsifier, lower the required amount C D Demulsifier Concentration CD (ppm) HLB Nonylphenol EON Nonylphenol Ethoxylates O/W W/O ,75 5, HLB D C D Demulsifier Concentration CD (ppm) EO-PO Block Copolymers HLB W/O Pluronics (R) 6200 O/W HLB D Pluronics (R) 6400 Stability (as time for 50% water separation) <1min 1-20 min min min min >200 min

44 44/54 What happens now if asphaltenes change in type or concentration? This term is now changing HLB M = x A HLB A + x D HLB D = 10 Two different effects need to be studied: Asphaltene concentration (change in X A ) = dilution by solvent allows to include all existing natural surfactants Asphaltene type (HLB A ) = change of crude oil

45 45/54 For a given crude oil (HLD A =cst) and a given demulsifier (HLB D = cst) What is the C* D at different C A? Optimum when HLB M = x D HLB D + x A HLB A = 10 Em. Stab. Stabilityy (V/Vo=0.5, min) 1, C A (Asphaltene Concentration ppm) 10,000 3,500 1, C* D ,000 C D C D (NP5.5EO Concentration, ppm) 1, C DT O/W T W/O C AT ,000 3,500 10,000 35,000 <10 min min min min >100 min C D (NP5.5EO Concentration, ppm) C (Asphaltene Concentration, ppm) A C D C A

46 46/54 Locus of minimum stability C* D vs. C A exhibits 3 branches and Threshold T C D C D (NP5.5EO Concentration, ppm) 1, C DT C* D O/W T W/O C AT ,000 3,500 10,000 35,000 C (Asphaltene Concentration, ppm) A <10 min min min min >100 min C A

47 47/54 Locus of minimum stability C* D vs. C A exhibits 3 branches and Threshold T C D C D (NP concentration, ppm) 1, EO 5.5 EO 10 EO Asphaltene concentration in crude oil For various demulsifiers (various HLB D ) ,000 10, ,000 C A (Asphaltene concentration, ppm) C A

48 48/54 C D Locus of minimum stability C* D vs. C A exhibits 3 branches and Threshold T C D (Tween 80 concentration, ppm) Furrial Hamaca O/W W/O Vic-Bihl T 5 10% ,000 2,000 5,000 C A. (Asphaltene concentration, ppm) < min min min min >100 min C A For various crudes (various HLB A ) and another demulsifier (Tween 80)

49 49/54 Proportional Regime (C D <C DT ; C A <C AT ) Unit slope in log-log plot C D overall C A C DT O/W T W/O crude interface X A C AT C D /C A = X D /X A = k C A water X* D HLB m = HLB A + khlb D 1+ k overall C* D Allows to estimate HLB A

50 50/54 1,000 Diluent = cyclohexane 4.75 EO Effect of diluent C D (NP concentration, ppm) EO 10 EO Asphaltene concentration in crude oil 10,000 Diluent = toluene C* D much lower ,000 10, ,000 C A (Asphaltene concentration, ppm) C D (NP concentration, ppm) 1, EO 10 EO 15 EO CRUDE OIL C A =10% ,000 1, ,000 C (Asphaltene Concentration, ppm) A C DT ± the same; C AT much higher

51 Graciaa A. et al. Langmuir 9, (1993) 51/54 Diluent : cyclohexane / toluene mixtures C* D 1, C = 1,000 ppm A in 50% Toluene in CycloHexane in Toluene % of cyclohexane in the mixture cyclohexane-toluene Seggregation of toluene close to interface

52 52/54 CONCLUSIONS Generalized formulation numerical concepts apply to Asphaltenes / Demulsifier mixtures Asphaltenes characteristics parameters may be estimated from proportional regime. Optimum Demulsifier Dosage depends on its hydrophilicity Its nature asphaltenes content (only below threshold) diluent or crude polarity These advances might lead to predict, design and optimize demulsifier formulations in the near future.

53 53/54 Thanks and Acknowledgments To my coauthors M. Rondón, J. C. Pereira, P. Bouriat, J. Lachaise, and A. Graciaa To our universities in France and Venezuela To different R&D programs, particularly RITMER and AGENDA PETROLEO projects. To the French-Venezuelan graduate cooperation exchange program (PCP) for PhD students To the organizers of this conference for inviting me to present this talk.

54 54/54 More info

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