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Introduction to OLI Studio: ScaleChem for First-Time Users

Updated

Disclaimer: The user interface, calculations, and results displayed in this article are from OLI Studio: ScaleChem Version 12.0.0. Other software versions may appear different or present slightly distinct results due to continual developments to the software and thermodynamic databanks.

Why Use OLI Studio: ScaleChem?

Understanding Scale Problems

Scale problems arise when a fluid initially in equilibrium with its environment is disturbed, leading to instability. This instability results in the partitioning of H2O, CO2, and H2S across water, oil, and gas phases, corrosion of metal surfaces, and the precipitation or dissolution of solids. Accurate simulation and understanding of these effects are crucial for oil and gas production professionals.

The Role of Precipitates

Precipitates form when the concentration of mineral-forming elements in produced waters exceeds supersaturation, often due to changes in pressure, temperature, phase partitioning, and fluid mixing. OLI Studio: ScaleChem quantifies the effects on mineral scale potential while calculating the physical and chemical properties of fluid and gas phases, helping industry professionals devise effective scaling management strategies.

Capabilities of OLI Studio: ScaleChem

OLI Studio: ScaleChem allows users to calculate scaling at various specified temperatures and pressures. Key features include:

  • Mixing waters at specified ratios to determine compatibility.
  • Saturating water with respect to one or more solids to simulate reservoir conditions.

Input Objects in OLI Studio: ScaleChem

OLI Studio: ScaleChem offers three types of input objects, also known as analysis types:

Brine Analysis: Refers to all waters and aqueous samples. Users can add a brine by double-clicking on "Add Brine Analysis." Brine compositions are entered in terms of ionic concentrations, with additional specifications for pH, total inorganic carbon, and alkalinity.

Oil Analysis: Allows the entry of non-aqueous phase oils. Oil samples may consist of pure component hydrocarbons (e.g., alkanes), distillation data, pseudocomponents, or a combination of these.

 

Gas Analysis: Allows the entry of any hydrocarbon mixture, which may include water, carbon dioxide, or hydrogen sulfide. The default hydrocarbon is methane (CH4), but the list can be expanded to include higher carbon numbers.

 

Calculation Objects in OLI Studio: ScaleChem

There are five types of calculations available:

Saturator: Combines fluids at specified temperatures and pressures, saturating the combined phases with selected minerals.

 

Facilities: Mixes and separates fluids to simulate production operations.

 

Scale Scenario: Calculates the scaling of minerals from a fluid as temperature and pressure change, such as at different production locations.

 

Scale Contour: Calculates the scaling of minerals from a fluid over a matrix of temperature and pressure, creating a 2D contour plot.

 

Mixing Water: Mixes two potentially incompatible brines to identify the ratios at which scale will form.

 

Entering Data for a Brine Analysis

Adding a Brine Analysis

  1. Go to the toolbar menu and click on Streams > ScaleChem > Add Brine.
  2. Alternatively, select the Add Brine Analysis icon in the Actions Pane.

 

 

Navigating the Brine Analysis Tabs

You will see three different tabs for this analysis:

  • Description
  • Design
  • Report

The Brine Analysis opens in the Design tab, which contains two sub-tabs: Data Entry and Reconcile.

Data Entry Sub-tab

In the Data Entry sub-tab, you will enter the laboratory analysis information, specifically the concentrations of cations, anions, and neutrals. This sub-tab comes prepopulated with common species found in laboratory water/brine analyses (default units are in mg/L).

Entering Species Concentrations

  • If a species is not present in the prepopulated grid, click on the white grid and type the ion or neutral of interest.
    • For cations, type the element followed by a plus (+) sign and the corresponding oxidation state (e.g., Cu+2).
    • For anions, type the element followed by a minus (-) sign and the corresponding oxidation state (e.g., Br-1).
    • For neutrals, type the species using either the formula name or its chemical name.

Search Aids

  • The grid contains drop-down lists to help find specific cations, anions, or neutral species. The lists are alphabetical and can be activated using the drop-down arrow within the cell after typing the first few letters of the ion.

Brine Analyses - Reporting Elements

Brine analysis data obtained from Inductively Coupled Plasma (ICP) measurements will often include concentrations for elements such as Boron (B), Phosphorus (P), Sulfur (S), and Silicon (Si). These elements do not exist in water as pure elements; instead, they exist as dissolved ions. If these elements are part of your analysis, you must convert them to their corresponding aqueous species before entering them into the Brine Analyses object in OLI Studio: ScaleChem.

Converting Element Concentration to Species for Brine Analysis

Here’s how to convert the concentrations of these elements to their respective aqueous species:

Boron (B)

  • Aqueous Species: Boric Acid
  • Formula to Enter: H3BO3
  • Formula Weight Multiplier: B (mg/L) × 5.72 = H3BO3 (mg/L)

Silicon (Si)

  • Aqueous Species: Silica
  • Formula to Enter: SiO2
  • Formula Weight Multiplier: Si (mg/L) × 2.14 = SiO2 (mg/L)

Phosphorus (P)

  • Aqueous Species: Dihydrogen Phosphate
  • Formula to Enter: H2PO4-1
  • Formula Weight Multiplier: P (mg/L) × 3.13 = H2PO4 (mg/L)

Sulfur (S)

  • Aqueous Species: Sulfate or Sulfide (depending on the form)
  • Formulas to Enter: HS-1 or SO4-2
  • Formula Weight Multipliers:
    • For Sulfide: S (mg/L) × 1.03 = HS-1 (mg/L)
    • For Sulfate: S (mg/L) × 3.0 = SO4-2 (mg/L)

Example Conversion

If your ICP measurement indicates:

  • Boron: 10 mg/L
  • Silicon: 15 mg/L
  • Phosphorus: 8 mg/L
  • Sulfur: 12 mg/L

You would convert these concentrations as follows:

  • Boron: 10 mg/L × 5.72 = 57.2 mg/L of H3BO3
  • Silicon: 15 mg/L × 2.14 = 32.1 mg/L of SiO2
  • Phosphorus: 8 mg/L × 3.13 = 25.04 mg/L of H2PO4-1
  • Sulfur:
    • For Sulfide: 12 mg/L × 1.03 = 12.36 mg/L of HS-1
    • For Sulfate: 12 mg/L × 3.0 = 36 mg/L of SO4-2

By using these conversions, you can accurately enter the concentrations of these elements into the Brine Analyses object in OLI Studio: ScaleChem, ensuring precise and reliable analysis.

Correcting Errors

  • If a name is misspelled or unrecognized, a red ‘X’ will appear to the left of the name. Correct the name or delete the row by selecting the wrong entry (which will turn black) and pressing the Delete key.

Reconcile Sub-tab

In the Reconcile sub-tab, you define the measured properties of the brine and instruct the software on how to reconcile the brine.

Entering Measured Properties and Conditions

  • Start in the Properties | Measured | Calculated table.
  • Default values for temperature and pressure are 25°C and 1 atm, respectively.
  • Enter measured values for properties in the aqua-blue cells, such as:
    • Measured pH
    • Measured Alkalinity
    • Density
    • Specific Electrical Conductivity
    • Total Dissolved Solids (TDS)

You can change the units of these properties by clicking on the blue-highlighted units, which opens the Units Manager Window. If you don’t have a measured property value (e.g., Specific Electrical Conductivity), leave it blank. The yellow cells under the Calculated column will display calculated values once the simulation is run.

Reconciliation Options in Brine Analysis - Definitions

When reconciling a Brine Analysis in OLI Studio: ScaleChem, you have five options:

  1. Concentration Data Only
    • Description: This option performs an electroneutrality reconciliation and computes water properties such as pH, density, etc., based on the entered concentrations of neutral species, cations, and anions.
    • Details: You can allow the program to automatically pick the species to adjust for electroneutrality, or manually choose the species for adjustment.
  2. Gas-phase CO2 Content (mole%)
    • Description: Useful when measuring gas-phase CO2 separated from the brine at the sampling point.
    • Details: This option, paired with another measured variable (usually alkalinity), allows the software to calculate the concentration of carbonate species and pH. The software performs a CO2 gas fraction calculation by taking the PCO2 and the calculated alkalinity to reconcile the system for pH and carbonate properties, adjusting CO2 to match a saturated gas composition.
  3. Measured pH Only
    • Description: Adjusts the brine analysis to match a reported measured pH.
    • Details: The software runs both an electroneutrality and pH reconciliation, matching the recorded pH and computing water properties like density and electrical conductivity. The pH is adjusted automatically by adding either HCl or NaOH, or you can select your preferred acids and bases for the adjustment.
  4. Measured pH and Alkalinity
    • Description: Matches computed pH and alkalinity values with measured values.
    • Details: The software runs electroneutrality, pH, and alkalinity reconciliations, computing water properties such as density and electrical conductivity. The pH is adjusted by adding HCl or NaOH, or other selected acids and bases. Alkalinity is calculated using CO2 as the titrant, H2SO4 as the pH titrant, and 4.5 as the endpoint pH. You can change the alkalinity titrant if preferred.
  5. Measured pH, Alkalinity, TIC
    • Description: Matches measured pH, total alkalinity, and total inorganic carbon (TIC).
    • Details: The software adjusts TIC using CO2 as the alkalinity titrant, H2SO4 as the pH titrant, and 4.5 as the endpoint pH. It adjusts acetate concentration to match total alkalinity by adding/removing acetic acid (this cannot be changed). The target pH is obtained using HCl or NaOH, or other selected acids and bases for pH adjustment.

Additional Option: Calculate Alkalinity

  • Description: This option only calculates alkalinity based on the entered concentrations and is not an alkalinity reconciliation.

By selecting the appropriate reconciliation option, the software will calculate the properties of the brine accordingly.

 

Adding a Gas Analysis

  1. Go to the toolbar menu and click on Streams > ScaleChem > Add Gas.
  2. Alternatively, select the Add Gas Analysis icon in the Actions Pane.

 

 

Navigating the Gas Analysis Tabs

You will see four different tabs for this analysis:

  • Description
  • Design
  • Definition
  • Report

The Gas Analysis opens in the Design tab, which contains two sub-tabs: Inflows and Reconcile.

Inflows Sub-tab

In the Inflows sub-tab, you enter the laboratory gas analysis information.

Entering Component Concentrations

  • Enter the concentration of a pure-component hydrocarbon gas in mole % units. The standard list includes components up to C6 alkanes.
  • If a component is not present in the prepopulated grid, click on the white grid and type the species of interest using the formula name or its chemical name. For example, to add Isooctane, type "isooctane" or "i-C8H18" in the white cell.
  • You can also use the drop-down arrow to search for and add specific components.

Correcting Errors

  • If a name is misspelled or unrecognized, a red ‘X’ will appear to the left of the name. Correct the name or delete the row by selecting the wrong entry (which will turn black) and pressing the Delete key.

Reconcile Sub-tab

The Reconcile sub-tab is used to calculate the properties of the gas at specified temperature and pressure conditions.

Entering Temperature and Pressure

  • By default, the values for temperature and pressure are 60°F (15.56°C) and 14.7 psia (1.002 atm).

Using these steps, you can effectively enter data for a Gas Analysis in OLI Studio: ScaleChem and perform necessary reconciliations to calculate the properties of the gas under specified conditions.

Entering Data for an Oil Analysis

Adding an Oil Analysis

  1. Go to the toolbar menu and click on Streams > ScaleChem > Add Oil.
  2. Alternatively, select the Add Oil Analysis icon in the Actions Pane.

 

 

Navigating the Oil Analysis Tabs

You will see three different tabs for this analysis:

  • Description
  • Design
  • Report

The Oil Analysis opens in the Design tab, which contains four sub-tabs: Combined, Pseudocomponents, Assay, and Reconcile.

Combined Sub-tab

In the Combined sub-tab, you can enter pure components (organic and inorganic).

Entering Components

  • If a component is not present in the prepopulated grid, click on the white grid and type the species of interest using the formula name or its chemical name. For example, to add Isooctane, type "isooctane" or "i-C8H18" in the white cell.
  • Use the "show non-zero only" option to hide all zero values, as they are not needed.

Pseudocomponents Sub-tab

In the Pseudocomponents sub-tab, you can enter pseudocomponents.

 

Entering Pseudocomponents

  • Provide the following information for each pseudocomponent:
    • Molecular Weight
    • Normal Boiling Point (NBP)
    • Specific Gravity (SG)
    • Thermodynamic Method
    • Mole%

Assay Sub-tab

In the Assay sub-tab, you can enter distillation curves. The Assay screen contains three data entry grids: Component, Entry Options, and Distillation Data.

Component Grid

  • Name your assay (no more than 5 letters allowed for the name).
  • The mole% represents the total hydrocarbon mass.

 

Entry Options Grid

  • Fill out the following information:
    • Assay Type: Choose from the following experimental methods used to create distillation curves:

      • ASTM D86: Runs at atmospheric pressure and is used for all oil types.
      • ASTM D1160: Runs at vacuum pressure and is used for heavy oils.
      • ASTM D2887: Runs on a gas chromatograph and is used for light oils.
      • TBP: The true boiling point curve.

 

    • Thermo Method: Choose from the following methods for calculating thermodynamic properties:

      • API-8: Uses specific gravity to determine critical parameters.
      • API-5: Uses specific gravity to determine critical parameters.
      • Cavett: Uses API gravity to determine critical parameters.
      • Lee-Kessler: Uses the Watson K to determine critical parameters.
    • Density: Provide the average bulk density using one of the following options:
      • Specific Gravity (SG): The ratio of the material density to water. Must be between 0.228 and 1.6.
      • API Gravity: Defined as API Gravity = (141.5/SG) – 131.5.
      • Watson K: Relates density to boiling point.
    • No. of Cuts: Specify the number of cuts.

Distillation Data Grid

  • Enter the distillation data in this section.

Reconcile Sub-tab

The Reconcile sub-tab is where equilibrium calculations are performed to calculate the properties of the gas at specified temperature and pressure conditions.

Entering Temperature and Pressure

  • By default, the values for temperature and pressure are 60°F (15.556°C) and 14.7 psia (1.002 atm).

Using these steps, you can effectively enter data for an Oil Analysis in OLI Studio: ScaleChem and perform necessary reconciliations to calculate the properties of the oil under specified conditions.

Putting Together a Complete Calculation in OLI Studio: ScaleChem

Now that we have defined some terms, we are ready to begin entering the information required to run a calculation. In this example, we will enter the concentrations of a single brine and calculate its scaling tendency.

Task 1 – Create a Brine Analysis

  1. Add Brine Analysis
    • From the Actions Panel, add a Brine Analysis.
  2. Description Tab
    • Click on the Description tab if it is not currently displayed. Enter the name “Brine”
  3. Enter Brine Chemistry
    • Enter the following concentrations, alkalinity, pH, and density information in the Design tab (Data Entry sub-tab):
Cations (mg/L) Anions (mg/L) Measured Properties
Na+1: 36000 Cl-: 57000 Temperature: 25°C
K+1: 300 SO4-2: 250 Pressure: 1 atm
Ca2+: 600 HCO3-1: 600 pH: 7.67
Mg2+: 150   Alkalinity: 600
Sr+2: 80   Density (mg/L): 1.064
Ba+2: 5   TDS (mg/L): 96280

  1. Select AQ Thermodynamic Framework
    • Ensure the AQ thermodynamic framework is selected for these calculations.
  2. Show Non-zero Only
    • Select the "Show non-zero only" box to display only species with actual concentrations.

Balance Option

    • Select the Dominant Ion balance option type.

Review the Dominant Ion Charge and Ions needed to balance in the tables presented in the Summary Box.

Reconcile Tab

    • Select the Concentration Data Only option.
    • Check the Calculate Alkalinity box.
    • Enter the measured pH (7.67), density (1.064 g/mL), and TDS (96280 mg/L).
    • Leave the Allow solids to form option unchecked.

Calculate

    • Select the Calculate button or press the <F9> key.
    • The calculated column will display results based on the entered concentrations, including a calculated pH of 7.43 and 564.26 mg/L as HCO3 in total alkalinity.

Report Tab

    • Scroll down to the Pre and Post Scaling Tendencies to find the results of Scaling Tendencies with Solids off.

Task 2 – Create a Scaling Scenario

Add Scale Scenario

    • Select Add Scale Scenario from the Actions panel.

  • This will display the design tab.

Inlets Tab

    • Select Brine in the Type column.

    • Select the brine created in Task 1 from the drop-down menu in the Name column.

    • Enter 1400 (bbl/day) in the Flow column. Change units if necessary

Description Tab

    • Rename the Scale Scenario as "Brine Scale Scenario."

 

Conditions Tab

    • Enter the following conditions for each location:

Location Temperature (C) Pressure (bar)
Reservoir 125 275
Bottomhole 125 280
Downhole 115 190
Midwell 105 130
Wellhead 100 100
Choke 90 80
Separator 60 30
    • As you build the calculation the design box updates. You can see how the process is connected.

    • The graphical view clearly shows the five locations and their Temperature and Pressure conditions.
    • The Drop Solids checkbox column is designed to help the users decide if they want to carry forward solids from certain locations or not.

Solid Tab

    • Ensure the solid button in the menu bar is selected.

    • Select the Standard checkbox.

Calculate

    • Press the Calculate button or select the <F9> key

Plot Tab

    • The default plot is to display the dominant pre-scaling tendencies v. location

View Data

    • The View Data button shows the pre-scaling tendency at each location.

Task 3 – Create a Gas Analysis

Add Gas Analysis

    • Double-click on the Add Gas Analysis object in the Actions Panel.

Description Tab

    • Rename the object to "Gas Analysis."
    • Select AQ Thermodynamic Framework
      • Ensure the AQ thermodynamic framework is selected for these calculations.
      • The same thermodynamic framework must be used for the Brine, Gas, and Oil in order to be utilized in the Scenario.

Inflows Grid

    • Enter the following composition and values:

Formula Component Name mole % Formula Component Name mole %
H2O Water 1.80 C3H8 Propane 8.00
N2 Nitrogen 3.00 i-C4H10 Isobutane 1.00
CO2 Carbon dioxide 1.50 n-C4H10 n-Butane 3.00
H2S Hydrogen sulfide 0.50 i-C5H12 Isopentane 0.50
CH4 Methane 65.5 n-C5H12 n-Pentane 0.70
C2H6 Ethane 14.0 n-C6H14 n-Hexane 0.50

 

Task 4 – Recalculate Scale Scenario with Gas

Add Gas to Scale Scenario

    • Select the “Brine Scale Scenario” icon in the navigator panel.

    • Select the Design Tab and then the Inlets tab.
    • In the Type column, add Gas.

    • In the Name column, select Gas Analysis.

    • Enter a flow rate of 250 std E3m3/day in the flow cell.

Calculate

    • Press the Calculate button or select <F9>.

Plot Tab

    • This should be the default plot (dominant pre-scaling tendencies)

    • Select the Variables button.
    • Remove all variables from the Y1 and Y2 axes.
    • Expand the Pre-scaling Tendencies and add CaCO3 (Calcite) to the Y1 Axis.

    • Expand the Additional Stream Parameters and add pH to the Y2 Axis.
    • Click OK.

View Data

    • The table will show the pre-scaling tendency at each location.
    • The plot view will show the decreasing calcite saturation trend and increasing pH.

By following these steps, first-time users can effectively utilize OLI Studio: ScaleChem to analyze brine, oil, and gas samples and calculate scaling tendencies under various conditions.

The completed example case is attached to this article.

 

 

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