Add fitted properties

Properties in the product can be modelled or non-modelled. Modelled properties are those properties included in the statistical model in the product. These properties were included in the original assays for the crude oil and so may be verified or predicted during generation of the assay.

Non-modelled properties are those properties which are not included in the statistical model. Some of these may be correlated or indexed to other properties (such as cetane index or API respectively). Other properties may not be routinely measured for crude oils, and so are not available through the statistical model.

The product contains an extensive list of properties, many of which are not modelled. For these properties it is still possible to generate property profiles using curve fitting of any available data. For modelled properties, property profiles are generated using the entered data, along with statistical modelling built into the product. However, for non-modelled properties, property profiles are generated using curve fitting of the available data.

Generating property profiles for non-modelled properties may be useful if your organisation commonly measures particular properties which are not included within the set of modelled properties. If property data is available for a crude and its products, the product will generate a property profile which can be recut for use in planning and scheduling tools, as well as for reporting.

For example, your organisation may commonly measure the organic chloride content of crude oil and its fractions. Organic chloride is not commonly measured for crude oils and so is not available in the standard statistical model of the product. Using curve-fitting, a property profile for organic chloride can be generated over the boiling range of the crude, and this can be recut for use in business reports.

1. Add a new Property to the Property Manager

   

   1. Open the Property Manager by clicking Properties in the Managers group of the Reference Data ribbon tab.

   2. Click the icon to add a new property.

   3. Enter a Name, choose a Unit Category and enter a DLL Code for the property.

   4. Click OK to create the property.

2. Configure the property's settings

   

   Select the new property in the left-hand list of the Property Manager and configure any additional settings.

3. Change the precision for the property's fitting

   

   5. Select the Test Methods page of the property by clicking the link in the left-hand side list.

   6. Double click the Default row. The Test Method Editor dialog box opens.

   7. In the Precision text field enter a formula for the precision. See below for more details on how to configure this field.

   8. If you have used the X symbol in your formula, from the where X is a value expressed in list choose the appropriate unit of measure.

   9. Click OK to confirm your choices.

   Each property has a precision value associated with it. The precision is the repeatability with which the property can be measured. The precision for a property can either be a fixed value, or can be calculated from the property's value using a mathematical formula.

   The precision can be obtained from the test method used for the property, or measured by laboratory analysts. It is necessary to enter the precision so that Assay can accurately calculate the property profile. If the precision is too large compared to the entered values Assay will not be able to calculate the property profile.

   For example, a precision of 10 means that the there is an uncertainty of ±10 associated with the measurement. Thus, if the measured value was 80, including the uncertainty it could be between 70 - 90. If the measured value was 2000, including the uncertainty it could be between 1990 - 2010.

   It is also possible to calculate the precision based on the actual value of the property. For many measurement methods the uncertainty varies with the property value and can be expressed using a mathematical formula. The example, max(10,0.01*X), shows that the uncertainty is the maximum value of either 10, or the property value multiplied by 0.01. If the measured value was 80 the precision would be the maximum of 10 or 0.01*80 = 0.8, so the precision would be ±10. Therefore the value could be between 70 - 90. If the measured value was 2000 the precision would be the maximum of 10 or 0.01 * 2000 = 20, so the precision would be ±20. Therefore the value could be between 1980 - 2020.

   After setting up the property's parameters click OK to close the Property Manager.

4. Create a new AssaySynthesis document for workup

   

   Create a new AssaySynthesis document by clicking the Add Document icon in the lower right corner of the Assay window, and selecting AssaySynthesis from the menu. Select the Measurements page in the new document, if not already active. If necessary, transpose the measurements grid by right-clicking on the grid and selecting Transpose from the context menu, so that rows correspond to properties and columns to cuts.

5. Enter the assay data in the measurements grid

   

   Enter the property measurements into the grid. To add a property, double click a cell in the Property column to reveal a list of properties. To add a cut, click and type in the column header cells to enter the cut name, start and end point.

6. Generate the assay

   To generate the assay, press F5 or click Generate in the Assay group of the Home ribbon tab. When the fit is complete, property values for the new assay appear in the upper right corner of each cell in the measurements grid.

7. Review the property profile

   

   To look at the generated profile for the new property you can use the Property profile graph.

   If the graph is not already visible, open it by clicking the lower half of the Graphs button in the Graphing group of the Home ribbon tab, and choosing Property Profile Graph from the menu.

   Make sure that the check box next to the LY Axis field is selected. Choose the new property from the list of properties for the LY Axis field.

   The product has fitted a profile to the entered data. This profile can be recut for use in planning and scheduling tools or reporting.

   Property profiles are only available for assays where measurements for the particular property are included along with the other assay data. If measurements for the particular property are not included, the product is not able to generate a property profile for the particular property.