Interaction of phosphonates onto the        immobilized surface:Application to scale control in oil and gas flow assurance...
Outline•   Background and previous batch study•   Hypothesis/Objectives•   Challenges and Methods•   Results•   Conclusions
Scale in water transporting system Scale in oil and gas flow assurance (CaCO3,  FeCO3 ,CaSO4, BaSO4, SrSO4 , etc.)   Cha...
How much scale could potentially form ?Scale tendency                        0, " undersatur ated" and calcite dissolves  ...
Scale control with threshold inhibitor Conventional onshore and Unconventional offshore reservoir    Pushing and fixing ...
Inhibitor return after squeeze treatment         1000                                                                     ...
Phosphonates attachment to calcite surface(Previous Batch Study) Solid Phase NTMP Conc. ( mol/m2 )                        ...
Solubility of Ca-Inhibitor precipitates(Previous Batch Study) Inhibitor   Stoichiometry    Solubility product             ...
Hypothesis Inhibitor may deposit and retain on the surface by working with  the possible scale, such as CaCO3 Scaling ri...
Challenges   No robust experimental method for kinetics study   Difficult to convert beaker result to real prediction  ...
Modified Plug flow reactorModified carbon steel tube (AISI1010, 5in length, ¼ in OD)   1. Coat the outer surface with rust...
Modified Plug flow reactor3. Precoat uniform CaCO3 layer on the subsurface  Provide constant surface area                 ...
Apparatus                          pump                                           Sample Collection &                     ...
Inhibitor attachmentC0= 680ppm, ΔSI_CaCO3= 0.6, 0.2-1330 mg/L DTPMP, pH= 5.9, 70C, Q=100ml/h for 1 hr                     ...
.                Inhibitor conc. effect on the attachment                 Inhibitor attachment on the calcite surface (sur...
Ca conc. effect on the attachmentCca= 612-3833 mg/L, 100 mg/L DTPMP, pH= 6.2, 70C, Q=100ml/h            1.2             1 ...
Ca conc. effect on the attachment                                       SI_CaCO3               0.8     1.0         1.2    ...
CaCO3 facilitates phosphonate retention                                                                          SI_      ...
Inhibitor release      Cca= 680 mg/L, ΔSI= 0.6, No DTPMP, pH= 5.9, 70C, Q=100ml/h             DTPMP conc. (mg/L)   100    ...
“Memory effect” of inhibitor release           100                                                     800                ...
Ca Concentration effect                   2.5                                                                             ...
Flow rate effect on the inhibitor release               100                                                     10 ml/hr  ...
1.4                           DTPMP S.S. Effluent Conc. (mg/L)                                                            ...
Pipe length at equilibrium (c=cs)Q=1000 bbl/d,       c/cs(DTPMP) I.D.=2.5-4 inch,      1.2v=22.7-57.9 cm/sec,      1km=2.8...
Inhibitor-Saturation Index RelationshipAt a specific T, SI, pH, and molar ratio (cation/anion) for                        ...
2.5                                                                2.25                                                   ...
Conclusion The phosphonate inhibitor layer was built up on the pipe  surface with CaCO3 pre-coated layer. Amount of inhi...
Acknowledgements       • Rice Brine Chemistry Consortium (BCC)       • Fellowship, China Scholarship Council       [Grant ...
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Sigma xi nanzhang_20130312_3

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  • In addition to corrosion and gas hydrates scale is one of the three important problems in any water transporting system (Figure 1-2).
  • In addition to corrosion and gas hydrates scale is one of the three important problems in any water transporting system (Figure 1-2).
  • Earlier understanding and optimizing squeeze design was based on the empirical differences between different scale with a specific inhibitor performance and the assumption that inhibitors reduce the growth rate by the fraction of inhibitor critical coverage adsorbed on the crystal surface
  • Long inhibitor return tail with a constant concentration
  • (Static Result ) Go through three phase in the squeeze phase.
  • The biggest challenges in kinetics study is to find a proper experimental method. Conventional beaker, rotating disc, and constant composition are three common method for crystal kinetic study. Constant composition method is so far the best method to provide a constant pH, SI, IS, but it is still a beaker experiment and cannot control the surface area. Therefore results from those research are hard to convert for real kinetics prediction, not mention the inhibitor performance.
  • Want to Build the inhibitor on the surface (CaCO3 surface)The second step, is to polished inner surface with 2000? Grid sandpaper to remove the grease on the surface. There is no commercial available tool to clean the inner surface, so we took a rod stock which is smaller enough to put into the carbon steel tube. Wrap the tip of the rod stock with sandpaper, and put the whole part on a driller. Then carefully polish the tube from end to end.
  • The pure tube has a fix surface area, if we can successfully develop a CaCO3 surface covering the inner surface of tube, then the surface area during experiment can be better controlled. So the third step, is to precoat the inner wall with a uniform film of CaCO3. This is a critical step of pretreatment to eliminate the initial preference attachment and to provide a fix surface area of CaCO3 for crystal growth.However, since there have been a systematic theory to explain the initial attachment of crystal on the subsurface. This step of pretreatment is more like a art than a science. After numerous attempts, it was found that a uniform layer of well adhered CaCO3 could be deposited using a room temperature feed solution containing 470 ppm Ca as CaCO3 in 0.1 M NaCl. and this solution was flowed through the reactor at 80C for about 12hours at a flow rate of 250ml/hr.
  • Temperature is the driving force for experiment to create delta SI.A schematic representation of the experiment apparatus is presented in this slids, Feed solution containing calcium and carbonate ions and equilibrium with 100% CO2 was pumped through the preheat coil and then to carbon steel pipe placed in a water bath. Of course we can use other heat source if higher temperature need to be reached. A back pressure regulator was installed at the end of test tube to insure the CO2 dissolve in the solution during the entire experiment. Sample was collected for ICP analysis and monitored by pH meter right after back pressure regulator. Now we are ready to use this reactor for the CaCO3 crystal growth rate.
  • Surprisingly, 1. the inhibitor can be continuously added to the surface 2. and the amount of the inhibitor attached is with a perfect linear relationship. If this only the complex of Phosphonate with the surface. That wouldn’t go to the 267 layer. Although the surface area that one inhibitor molecule occupies is not known with certainty, it can be estimated by varous model assumptions and by avagadro’s number that 1 mg of inhibitor probably occupies approximately 1 m2 of surface area.
  • Break through didn’t occur like what happen when we change the inhibitor conc. We don’t know the reason yet, but we do realize the with increasing of ca conc. more calcium can be build up on the surface. Could be the CaCO3 and CaPhncoprecipitation !!!!!!!!!!!!!!!! So we took 1 hour injection data, do the integration to see how much total inhibitor attached on the surface
  • For 1 hour
  • For 1 hour
  • With this amount of
  • In order to prevent a solution from scaling with a higher SI CaCO3, it is desired to increase the return conc. We already know the ppt on the surface is control by the CaCO3ppt and CaPhnppt
  • Dissolution can be described as a first order reaction ???0.17 cm/sec= ~480 ft/d
  • Conclusion + Implication
  • Sigma xi nanzhang_20130312_3

    1. 1. Interaction of phosphonates onto the immobilized surface:Application to scale control in oil and gas flow assurance Nan Zhang Rice University nanzhang@rice.edu March, 2013
    2. 2. Outline• Background and previous batch study• Hypothesis/Objectives• Challenges and Methods• Results• Conclusions
    3. 3. Scale in water transporting system Scale in oil and gas flow assurance (CaCO3, FeCO3 ,CaSO4, BaSO4, SrSO4 , etc.)  Changes of temperature and pressure.  Variations of pH and CO2/H2S partial pressure during operation.  Mixing of incompatible waters.  Effect of other constitnents. Fouling in heat exchanger (CaCO3, CaSO4, etc.) Fouling on the membrane surface (CaSO4, BaSO4 ,etc.)
    4. 4. How much scale could potentially form ?Scale tendency 0, " undersatur ated" and calcite dissolves SI zero, " equilibriu m" and scale doesn t form 0, " supersatur ated" and calcite precipitates
    5. 5. Scale control with threshold inhibitor Conventional onshore and Unconventional offshore reservoir  Pushing and fixing inhibitors into the formation via squeeze treatment  Inject trace inhibitors downhole via a treat string Unconventional onshore reservoir  Inject trace inhibitors with the fracturing fluid DTPMP NTMP (methylene phosphonic acid) (Methylene phosphonic acid)
    6. 6. Inhibitor return after squeeze treatment 1000 1000 Phosphonate (mg/L) 100Phosphonate (mg/L) 100 Gladys McCall N. R. Smith 10 10 1 1 0 0 3.E+01 1.E+07 2.E+07 3.E+01 5.E+05 1.E+06 2.E+06 Volumes of Produced Water (bbl) Volumes of Produced Water (bbl) Minimum Downhole Ca Well Name TDS (mg/L) ΔSI Inhibitor Temperature (F) (mg/L) Needed Gladys 298 96340 4130 1.04 0.18 McCall N.R. Smith 160 50899 480 0.43 <0.7 Inhibitor return concentration is dropping to a few mg/L level in the early flowback stage, but the interaction mechanism between the phosphonate inhibitor and scale is unclear, so the return concentration of the inhibitor is unpredictable.
    7. 7. Phosphonates attachment to calcite surface(Previous Batch Study) Solid Phase NTMP Conc. ( mol/m2 ) 100000 10000 3, Heterogeneous crystal growth 1000 precipitation 100 10 2, Crystal growth 1 0.1 Tomson et al., SPE, 2003 1, Langmuir adsorption 0.01 0.00001 0.001 0.1 10 1000 Solution Phase NaNa42NTMP Conc. (mmol/L) Solution Phase 4H H2 NTMP Conc. (mmol/L) Adsorption Langmuir adsorption Crystal growth CaCO3 Amorphous growth Kan et al., JCIS, 2005
    8. 8. Solubility of Ca-Inhibitor precipitates(Previous Batch Study) Inhibitor Stoichiometry Solubility product PKsp at 1 M Solubility1 I, 70 ºC (mg/L) NTMP CaH4P 32.46 32.46 22502 Ca2.5HP (am) 32.96 - 6.88 I(M) 2.17 I(M) 2380 / T(  K ) 21.31 174 Ca2.5HP (cr) 32.92 - 5.32 I(M) 1.76 I(M) 2023 / T(  K ) 23.46 0.92 Fe2.5HP (aged) 39.54 - 6.14 I(M ) 2.18 I(M ) 1315 / T(  K ) 31.74 0.0953 DTPMP Ca3H4P (am) 50.5 @ 1 - 2 M I, 70 C 50.5 250 Ca3H4P (cr) 58.95 0.048 I(M) 2084.5 / T(  K) 52.9 1.05 BHPMP Ca4H2P (am) 35.41 385 48.11 - 2.65 I(M) 3448 / T(  K ) Ca4H2P (cr) 48.46 - 2.60 I(M) 2998 / T(  K ) 37.12 7.0 PPCA Ca3(A·A·A)2 16.35 + 0.24·I(M) –252.1/(T( K) - 252.1) 13.82 1.45 (aged) Kan et al. Biogeochemistry of chelating agents chapter 15, 2005 The formation of CaPhn/FePhn precipitates with a low solubility may contribute to the low inhibitor return concentrations
    9. 9. Hypothesis Inhibitor may deposit and retain on the surface by working with the possible scale, such as CaCO3 Scaling risk can be controlled with a pulse injection of inhibitorObjectives1. Develop a CaCO3 pre-coated steel tubing for studies of CaCO3 crystal growth kinetics and inhibition kinetics.2. Evaluate the attachment kinetics of inhibitor on the surface3. Investigate the detachment kinetics and equilibrium of inhibitor from the surface and its inhibition impact on the CaCO3 scaling to the pipe.
    10. 10. Challenges  No robust experimental method for kinetics study  Difficult to convert beaker result to real prediction  Limited information on inhibitor performance Modified Conventional Rotating Constant Plug flow Plug flow Method free drift disc composition reactor reactor (this study) Surface area Variable Constant Variable Variable ConstantSaturation index Variable Variable Constant Constant Constant Ionic strength Variable Variable Constant Constant Constant pH Variable Variable Constant Constant Constant Hydraulic No Yes No Yes Yes condition Ultra High Hard Hard Hard Easy EasyTemp/Pressure
    11. 11. Modified Plug flow reactorModified carbon steel tube (AISI1010, 5in length, ¼ in OD) 1. Coat the outer surface with rust-oleum for corrosion control 2. Polish inner surface with sandpaper to create a smooth surface for CaCO3 deposition
    12. 12. Modified Plug flow reactor3. Precoat uniform CaCO3 layer on the subsurface Provide constant surface area Tubing surface area Eliminate initial preferential attachment A=18.3 cm2 Crystal surface area A=55 cm2 1.02 1.00 Ca Conc. Calcite 0.98 0.96C/C0 0.94 0.92 0.90 0.88 0.86 0.84 Aragonite 0 2 4 6 8 10 12 Time (hr)
    13. 13. Apparatus pump Sample Collection & Analysis: ICP, ICP-MS Soln. A Reactor: CaCl2+ NaCl Carbon steel AISI1010 tubing pre-100% CO2 coated with CaCO3 75 psi Soln. B pump NaHCO3+ NaCl Water Bath Parameter Value ICP_MS STD P Flow rate 10 -250 ml/min 0.6 Reactor I.D. 1/8 inch 0.5 Intensity Reactor Length 5 inch 0.4 y = 0.001x 0.3 R² = 0.999 Temperature 70 °C 0.2 Reactor volume 2.09 cm3 0.1 Residence time 75sec- 12.6 min 0 Reynolds’s 0 200 400 600 9-100 P conc. (ug/L) number
    14. 14. Inhibitor attachmentC0= 680ppm, ΔSI_CaCO3= 0.6, 0.2-1330 mg/L DTPMP, pH= 5.9, 70C, Q=100ml/h for 1 hr 1.2 DTPMP Effluent C/C0 1 0.8 0.6 0.4 0.2 Time (min) 0 0 10 20 30 40 50 0.2 mg/L 2.5 mg/L 5 mg/L 50 mg/L 100 mg/L 363 mg/L 1331 mg/L K tracer • The break through occurs in 20 min • Inhibitor cannot accumulate on the surface with time
    15. 15. . Inhibitor conc. effect on the attachment Inhibitor attachment on the calcite surface (surface area 55cm2) DTPMP f=129.4087*(1-exp(-0.0145*x)) DTPMP (retaine 140 (injected) d) 120 q 100 mg/L mg/m2 q (mg/m2) 80 0.22 0.20 60 2.5 2.01 40 5 7.05 10 18.73 20 47 56.89 0 0 200 400 600 800 1000 1200 1400 102 107.39 DTPMP (mg/L) 363.6 127.10 1331.8 128.78
    16. 16. Ca conc. effect on the attachmentCca= 612-3833 mg/L, 100 mg/L DTPMP, pH= 6.2, 70C, Q=100ml/h 1.2 1 C/C0 0.8 0.6 0.4 0.2 Time (min) 0 0 60 120 180 240 300 360 420 480 Ca=612 mg/L Ca=1704 mg/L Ca=3833 mg/L • The break through didn’t occur • Inhibitor can accumulate on the surface with time
    17. 17. Ca conc. effect on the attachment SI_CaCO3 0.8 1.0 1.2 1.4 1.6 1.8 1100 SI_ DTPMP SI_ 1000 Ca vs q Ca Ca3H4 (retained q SI_CaCO3 vs q DTPM CaCO3 for 1 hour 900 P injection)q (mg/m2) mg/ 800 mg/L mg % m2 700 612 1.76 0.9 3.4 33 618 1704 1.85 1.35 4.6 50 836 600 3833 1.77 1.73 5.3 52 1019 500 0 1000 2000 3000 4000 Injected Ca (mg/L) • Both Ca3H4DTPMP and CaCO3 precipitates affect the inhibitor attachment
    18. 18. CaCO3 facilitates phosphonate retention SI_ 1200 SI_ Ca HCO3 Ca3H4 q 1000 DTPM CaCO3 P 800 mg/q (mg/m2) mg/L m2 600 579 1224 2.09 0.01 59.2 583 1770 2.02 0.34 60.64616 400 581 2538 1.86 0.66 71.1 200 612 3274 1.76 0.9 609 0 1704 3274 1.85 1.35 835 0.0 0.5 1.0 1.5 2.0 CaCO3 SI 3833 3274 1.77 1.73 966 • SICaCO3 > 0.9, Ca concentration control the inhibitor attachment • SICaCO3 > 0.6, Phosphonates concentration control the inhibitor attachment
    19. 19. Inhibitor release Cca= 680 mg/L, ΔSI= 0.6, No DTPMP, pH= 5.9, 70C, Q=100ml/h DTPMP conc. (mg/L) 100 q= 4.75 mg/m2 102.5 mg/L DTPMP 2 47.4 27.9 mg/m q= mg/L DTPMP 10 2 10 mg/L mg/m q= 125 DTPMP 2.5 mg/Lmg/m2 q= 267 DTPMP 1 0.25 0.02 mg/L 0.1 0.01 60 80 100 120 140 Time (min)DTPMP return• starts with a short desorption and then followed by a long term dissolution process.• doesn’t change with the amount of inhibitor attachment on the surface conc.
    20. 20. “Memory effect” of inhibitor release 100 800 0.30 800 0.25 80 600 600 DTPMP (mg/L)DTPMP (mg/L) Ca (mg/L) 0.20 Ca (mg/L) 60 400 0.15 400 40 0.10 DTPMP 200 200 20 Ca 0.05 DTPMP Ca 0 0 0.00 0 0 500 1000 1500 2000 2500 0 100 200 300 400 500 600 700 Time (min) Time (min) DTPMP Injection DTPMP Protection q (injected) time (retained) time mg/L hr mg % mg/m2 hr 0.22 1 0.003 1.04 0.41 5.7 47.4 1 0.69 1.45 125 17 SI_CaCO3=0.59
    21. 21. Ca Concentration effect 2.5 4500 4000 2.0 DTPMP (mg/L) 3500 Ca (mg/L) 3000 1.5 2500 SI=0.29 SI=0.74 SI=1.1 SI=-3.3 SI=-0.28 1.0 2000 1500 0.5 1000 500 0.0 0 180 240 300 360 420 480 DTPMP Ca Time (min) Ca HCO3 SI pH mg/L mg/L • Ca precipitation and dissolution were both prevented.612.37 1643.73 0.29 5.891703.86 1643.73 0.74 5.90 • DTPMP failed when SI_CaCO3 > 1.13969.95 1643.73 1.11 5.92 5.88 • DTPMP return increased with a lower SI_CaCO3 . 0.175 1643.73 -3.25163.69 1691.89 -0.28 5.88
    22. 22. Flow rate effect on the inhibitor release 100 10 ml/hr Return LinearDTPMP (mg/L) Q DTPMP 50 ml/hr Velocity 10 Steady state 100 ml/hr 250 ml/hr ml/hr cm/sec mg/L 10 0.017 1.3 1 50 0.08 0.4 100 0.17 0.25 250 0.42 0.12 0 60 110 160 210 260 310 360 Time (min)
    23. 23. 1.4 DTPMP S.S. Effluent Conc. (mg/L) 1.2 1.0Advection Dissolution 0.8 0.6 0.4 0.2 0.0 0 200 400 600 800 L/v £s(sec) Return Overall Mass Linear DTPMP Solubility Dissolution transfer Velocity Steady (cs) rate rate state constant (k) constant cm/sec mg/L mg/L sec-1 cm/sec 0.017 1.3 0.08 0.4 2.86 1.73 0.0018 0.17 0.25 E-4 0.42 0.12
    24. 24. Pipe length at equilibrium (c=cs)Q=1000 bbl/d, c/cs(DTPMP) I.D.=2.5-4 inch, 1.2v=22.7-57.9 cm/sec, 1km=2.86 E-4 cm/sec, 0.8c/cs=1-exp(-3)=0.95L=1250-3200 ft 0.6 0.4 ID=4 inch ID=2.5 inch 0.2 0 0 1000 2000 3000 4000 pipe length (ft)
    25. 25. Inhibitor-Saturation Index RelationshipAt a specific T, SI, pH, and molar ratio (cation/anion) for Bariteeach specific inhibitor concentration, CInh (mg / L)there is a ,unique saturation index value, SI Bartiefor those conditions. ,These were solved for using Goal Seek. Illustrated here forbarite, the same applies for calcite. a2 a3 a4 t0Barite 10 ^ a1 SI Barite TK SI BartieTK Barite b3 [ Ba 2 ]M b Inh b1 b2 SI Bartie b4 pH b5 log10 2 TK [ SO4 ]M Barite Bartie Barite 1 f safety t Inh CInh (mg / L) Barite log10 bInh t0Barite
    26. 26. 2.5 2.25 Barite Calcite and barite Saturation IndexesDTPMP (mg/L), blue diamonds 2 2 1.75 1.5 1.5 Calcite 1 1.25 1 0.5 0.75 0 0.5 0 1000 2000 3000 4000 5000 6000 Feet of flow in 2.5in. pipe with Ca-DTPMP on steel surface
    27. 27. Conclusion The phosphonate inhibitor layer was built up on the pipe surface with CaCO3 pre-coated layer. Amount of inhibitor attached is related with the DTPMP adsorption on the CaCO3 surface. CaCO3 can facilitate the inhibitor attachment on the surface, may suggest the copercipitation of CaCO3 and CaPhn crystal. The DTPMP return is controlled by the dissolution of the Ca3H4DTPMP precipitates attached on the surface with a dissolution rate about 0.0018 cm-1. Ca precipitation and dissolution were both prevented.
    28. 28. Acknowledgements • Rice Brine Chemistry Consortium (BCC) • Fellowship, China Scholarship Council [Grant 2008102375] (2008-prsent) • DOE (DE-FE0001910) •Dr. Mason Tomson and Dr. Amy Kan

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