Nitrate-Rock Interaction

[jeffery79]

Hello,
I am a beginer in PHREEQC trying to modify exampls in the manual to solve my problem. What I want to do is to inject Nitrate into a sandstone rock and analyze the effects of Nitrate-rock interaction on sandstone rock petrophysical properties (mineral dissolution and precipitation). i keep having inconsistent result from minerals dissolved and precipitated.
Below is my input file.

SOLUTION 1 Pure Water
    temp      25
    pH        7
    pe        4
    redox     pe
    units     ppm
    density   1
    Ag        0.29
    Al        3
    Cl        0.3
    Fe        0.5
    K         0.87
    Na        0.43
    Oxg       64.2
    Si        30.38
    -water    1 # kg

EQUILIBRIUM_PHASES 1
    Calcite   0 0.5
    Illite    0 0.5
    Kaolinite 0 0.5
    Quartz    0 0.5

REACTION 1
    NaNO3      1
    0  0.001  0.005  0.01  0.03  0.05 moles

SELECTED_OUTPUT 1
    -file                 selected_output_1.sel
    -totals               N(5)
    -equilibrium_phases   Quartz  Calcite  Kaolinite  Illite
    -saturation_indices   Quartz  Calcite  Kaolinite  Illite

USER_GRAPH 1
    -headings               Quartz Calcite Kaolinite Illite SI_Quartz SI_Calcite SI_Kaolinite SI_Illite
    -axis_titles            "Nitrate added in millimoles" "Millimoles dissolved" "Saturation Index"
    -chart_title            "Nitrate_Sandstone Rock Interaction"
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
    -plot_csv_file          Nitrate and Sandstone
    -plot_csv_file          Quartz Calcite Kaolinite Illite SI_Quartz SI_Calcite SI_Kaolinite SI_Illite
  -start
10 x = RXN * 1e3
20 PLOT_XY x, 1e3 * (0.5 - EQUI("Quartz")), symbol = Plus
30 PLOT_XY x, 1e3 * (0.5 - EQUI("Calcite")), symbol = Plus
40 PLOT_XY x, 1e3 * (0.5 - EQUI("Kaolinite")), symbol = Plus
50 PLOT_XY x, 1e3 * (0.5 - EQUI("Illite")), symbol = Plus
60 PLOT_XY x, SI("Quartz"), y-axis = 2, line_width = 3, symbol = Circle, Color = Magenta
70 PLOT_XY x, SI("Calcite"), y-axis = 2, line_width = 3, symbol = Circle, Color = Red
80 PLOT_XY x, SI("Kaolinite"), y-axis = 2, line_width = 3, symbol = Circle, Color = Blue
90 PLOT_XY x, SI("Illite"), y-axis = 2, line_width = 3, symbol = Circle, Color = Green
  -end
    -active                 true


Or do you have any examples of input files that I can modify to run my simulations?
I really appreciate your reply. Thank you.

[dlparkhurst]

Addition of NaNO3 is not going to have a large effect on solubility compared to dissolution in pure water. The main effect is the increase in ionic strength that affects the activity coefficients of the dissolved ions.

Look closely at the saturation index axis. The SIs are only varying at the level of 1e-15.

[jeffery79]

Sorry I could not reach you immediately because i have been struggling. But Thank you for the advice and guidiance. well appreciated.
However, Now I wish to model the effect of oilfield chemical-rock interaction on mineral dissolution/precipitation. the parameters for the model are;

Materials
Rock type – Carbonate Rock
Elemental composition
Mg (5.79 wt%)
C (5.16 wt%),
O (70.20 wt%)
Ca (10.88 wt%)
Al (2.20 wt%)
K (0.65 wt%),
Cl (0.44 wt%),
Si (4.30 wt%)
Fe (0.38 wt%).
Mineral composition
dolomite (73.8 wt%)
calcite (21.2 wt%)
quartz (3.7 wt%)
pyrite (0.2 wt%)
halite (0.2 wt%)
multi-layer illite/smectite (0.9 wt%)
Chemical used for the reaction - glutaraldehyde (C5H8O2)

Please provide me a code i can use to model this interaction. Thanking you as I look forward to yur response. I must confess though, you have been great with your teachings and i COULD NOT understand how you are able to attend to everyone else like me who has been bamboozled by PHREEQC.

 

[dlparkhurst]

Why don't you start by defining a SOLUTION of pure water and react with an EQUILIBRIUM_PHASES definition containing all of the minerals.

[jeffery79]

Hello Sir, Please see my code as directed below and file attached for my output file.

SOLUTION 1
    temp      25
    pH        7
    pe        4
    redox     pe
    units     ppm
    density   1
    -water    1 # kg

EQUILIBRIUM_PHASES 1
    Calcite   0 0.31
    Dolomite  0 1.7
    Halite    0 0.08
    Illite    0 0.41

Thanking you for the time

[dlparkhurst]

You must consider what it is you want to do.

[jeffery79]

Thank you for the response. What I intend to do is react oilfield chemicals on rock dissolution/precipitation to see the effect on the strength of rocks and to quantify the effects of these chemicals on sand failure. Another issue I have is that I cannot find the desired chemicals such as amino trimethylene phosphonic acid (ATMP), biocide (glutaraldehyde) and betaine in the PHREEQC data. What can I do about the absence of these chemicals i desire to use in the PHREEQC data? Wht data file can i use?
Please advice.

Thank you sir.

[dlparkhurst]

I am not sure how much PHREEQC will help you. There are a number of ligands included in the llnl.dat and minteq.v4.dat databases, but not the ones that you list. If your ligands are present in significant concentrations, they could make a difference in the solubility of minerals. You will need either to find thermodynamic data for the equilibrium constants for complexing with your ligands and add the definitions in the input file (or database), or try to guess suitable analogues from the ones that are available in the databases.

As for diminishing the strength of rock, PHREEQC is limited to estimating the amount of dissolution of the various minerals (as you calculated in the solubility calculation). TRANSPORT simulations can be used to consider flow rates of solutions through the medium. However, the relation between the strength of rock and the amount of dissolution is a more complicated question that is not addressed by PHREEQC.