Molecular Thermodynamics of

Brine Chemistry

Chau-Chyun Chen

Jack Maddox Distinguished Engineering Chair

Department of Chemical Engineering

Texas Tech University

Presented at the UpTec Workshop, May 16, 2014

Slide 1

Slide 2

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1901/

Composition of Oilfield Produced Water

Slide 3

Igunnu and Chen, Int J Low Carbon Tech., 2012, 0, 1-21; Lou et al., 2014

Composition of Oilfield Produced Water

Slide 4

Igunnu and Chen, Int J Low Carbon Tech., 2012, 0, 1-21; Lou et al., 2014

Anions

Cations

Slide 5

Lou et al., 2014

Slide 6

Lou et al., 2014

Slide 7

Lou et al., 2014

Slide 8Accurate thermodynamic model is the scientific foundation of process simulation

Slide 9Accurate thermodynamic model is the scientific foundation of process simulation

Composition of Brines/Injection

Water/Formation Water

Slide 10

Fluid Phase Equilibria, 2014, 373, 43-54

Slide 11

Fluid Phase Equilibria, 2014, 373, 43-54

Important Salts in Hexary Oceanic Salt

Systems (Na+/K+/Mg2+/Ca2+,Cl-/SO42-)

Slide 12

Pure Appl Chem, 2001, 73, 831-844

Slide 13

Pitzer’s Ion-Interaction Model

Slide 14

Slide 15

Pure & Applied Chemistry, 2001, 73, 831-844

Slide 16

Pitzer Model for Hexary Oceanic Salt

Systems (Na+/K+/Mg2+/Ca2+,Cl-/SO42-)

o 3 parameters per binary and additional 2 per ternary

o 8 binary and 16 ternary systems

o 56 isothermal parameters and additional 2 for 2-2 valent

electrolytes (MgSO4 and CaSO4) -> 58 parameters

o Parameters & code available in PHREEQC, ChemApp,

GEMS, MINEQL+, etc.) for room temperature applications

To cover 0 to 200 °C, up to 8 temperature coefficients are

necessary for each Pitzer parameter -> 464 coefficients

Predictive power limited at ionic strength > 6 molal

Need models with smaller number of parameters -> one

general approach is NRTL+xDH

Slide 17

Pure Appl Chem, 2011, 83, 1015-1030

Slide 18

Electrolyte NRTL Model

Slide 19

I&ECR, 2009, 48, 7788-7797

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Development of TTU Thermodynamic

Model for Brines & Produced Water

Based on symmetric electrolyte NRTL model

An industry standard and a comprehensive thermodynamic

model capable of handling aqueous electrolytes, nonaqueous

electrolytes, nonelectrolytes, ionic liquids, etc.

Successfully used to model scale formation in oil reservoirs

during water injection, CO2 capture with amines, and CO2

solubility in saline water

Cover temperatures up to 200 °C and salt concentrations up to

saturation

Code available in Aspen process simulator

Slide 20

eNRTL Model for Hexary Oceanic Salt

Systems (Na+/K+/Mg2+/Ca2+,Cl-/SO42-)

2 parameters per binary and additional 2 per ternary

8 binary and 16 ternary systems

48 isothermal parameters

To cover 0 to 200 °C, up to 3 temperature coefficients

are necessary for each eNRTL parameter -> 144

parameters (vs. 464 for Pitzer)

Predictive up to saturation

Slide 21

Pure Appl Chem, 2011, 83, 1015-1030

Slide 22

Model Development: KCl-H2O Binary

Slide 23

Model Development: KCl-NaCl-H2O

Ternary

Slide 24

NaCl-Na2SO4 at 25 °C

Slide 25

NaCl-MgCl2 at 25 °C

Slide 26

MgCl2-MgSO4 at 25 °C

Slide 27

MgCl2-MgSO4 at 75 °C

Slide 28

MgSO4-Na2SO4 at 25 °C

Slide 29

Astrakhanite: MgSO4.Na2SO4.4H2O

MgSO4-Na2SO4 at 75 °C

Slide 30

Loweite: 2MgSO4.2Na2SO4.5H2O; Vanthoffite: MgSO4.3Na2SO4

Next Steps

Molecular thermodynamic model for the hexary

oceanic salt system within ~12 months

Molecular thermodynamic model for hydraulic

fracturing (adding Ba2+/Sr2+, HCO3-,) within ~24

months

TTU models should support process modeling and

simulation of produced water treatment processes and

mixing of brines/produced water

TTU models should have applications in many other

fieldsSlide 31