Blend

Assay allows you to blend together an unlimited number of crudes, giving ratios either as weight or volume proportions, to produce another crude description which can be added to the Database and manipulated in the same way as any other crude in the Database.

In depth: You can use Blend when you know the constituent crudes and their ratios (either weight or volume) in the blend. For example, suppose you have a mixture of crudes, and further, that you know the mixture's composition. You can use the Blend tool to give you accurate property information on the mixture without having to perform a time-consuming and costly assay.

To create a new Blend document, do either of the following:

• Click the button at the bottom of the Navigator pane and choose Blend from the menu.

• Click the New button in the Document group of the Home ribbon tab and choose Blend from the menu.

The normal process for creating model-based crude descriptions using Blend is described in the following sequence.

1. Enter non-numeric information

   You can enter non-numeric information about the crude using the Information page. This page lists a number of properties associated with the crude being worked up in the document, such as name, reference and comments.

   

   The Information page contains all the fields and data present in the Crude Summary dialog available in the Database view for the crude currently being processed. See Crude summary dialog.

   Tip: The assay Name and Reference can be also edited directly from the document tab in the Navigator pane, by double-clicking the relevant field and entering the text directly into the field. See Document pages.

2. Add crudes to the Blend

   

   To specify a blend, you must provide a list of constituent crudes, together with their weight or volume proportions in the final mixture.

   Click the Add button at the bottom of the Blending page to add one or more crudes to the blend list. The Select Crudes dialog opens. See Select crudes.

   

   Another way to add a blend constituent is to double click on any empty area of the Blending page.

   You can also add multiple items at a time from the database into the blend crude list by copying and pasting:

   1. Select the crudes you want to add in the database window.

   2. Press Ctrl + C or click the Copy button in the Clipboard group of the Home ribbon tab.

   3. Do either of the following:

      • Click Paste in the Clipboard group of the Home ribbon tab.

      • Right click in the blend crudes list and select Paste from the context menu.

        Once you have added a crude, you can edit it in the following ways:

   • To replace the crude, double click either the Reference or the Name cell. The Select Crudes dialog opens, allowing you to choose another crude.

   • Change the ratio of the crude in the blend by double clicking the value in the Ratio column and typing a new value. The ratio determines the proportion, by either weight or volume, of the crude in the final blend mixture. For example, a mixture of Arab Light, Kirkuk Blend and Basrah Light in the ratio 1:2:3 gives a blend that is one sixth Arab Light, one third Kirkuk Blend, and one half Basrah Light. The values in the % Wgt and % Vol columns, showing the equivalent percentages of the crude by weight and by volume, are updated automatically when you change the ratio.

     Tip: It is also possible to select assays for blending from the Database module. Select the required assays, right click and choose Create Blend from the context menu. Alternatively, click Create Blend in the Database group of the Home ribbon tab. This will copy the selected assays to the Blend module replacing any assays that are currently selected.

     Weight or Volume option

     

     The start ratios may either be in weight or volume proportions. To switch between these two options, choose the appropriate option from the Blend Using drop-down menu at the bottom of the page.

     Negative Coefficients

     

     Assay allows you to reverse the operation of blending by subtracting out one or more known blend constituents from a given blend. This is accomplished by specifying negative ratio weightings for the constituents being factored out of the blend.

     Managing the list

     You may add items to the blend crude list, edit items in the list and remove items from the list in a number of ways:

   • Right click on the crude list and choose Add, Edit or Remove from the menu.

   • Add a blend item by double clicking in the white space below the current list of crudes in the blend.

   • Click the Add, Edit and Remove buttons at the bottom of the Blending page.

     Copying and pasting data

     You can copy and paste crudes in the crude list to other crude lists in Assay, or to other programs using cutting, copying and pasting functionality. This can be accessed in a number of ways:

   • Click the Cut, Copy and Paste buttons in the Clipboard group of the Home ribbon tab for cut, copy and paste respectively.

   • Right click on the crude list and choose Cut, Copy and Paste from the context menu.

   • Use the keyboard shortcuts Ctrl + X, Ctrl + C and Ctrl + V

     Copying an item will place a copy of the information associated with that crude item onto the Clipboard, from where it can be pasted into other crude lists, or into an external application, such as Microsoft® Excel®. Conversely, data formatted in a recognisable way may be pasted from external programs into the Assay crude lists. Cutting an item copies it to the Clipboard, before permanently removing it from the crude list.

3. Generate the blend

   After entering all blend crudes into the Blend document, you can generate the crude at any time by clicking the Generate button in the Assay group of the Home ribbon tab (Generating a crude).

   Warnings

   There can be entries in the blend crude list which make the list unsuitable for use in the Blend tool. These cases occur in the following cases:

   • Any of the blend ratios are numerically invalid.

   • The sum of all negative ratios (for blend constituents being subtracted from the blend) outweigh the sum of all positive ratios.

     In addition, it is possible that a blend with negative coefficients may not be well defined. This can occur in the following cases:

   • Negative values for a blended crude result from a blend with negative coefficients. For example, removing 50% of a sour crude from a sweet crude may result numerically in negative sulphur values.

   • The limit of negative to positive ratios tends to -1. For example, blending two crudes with ratios of 2 and -1.999 respectively may result in a blend that exhibits ill-defined behaviour.

4. Review the blend

   After generating the blend it is possible to review the blend on the Property Profile Graph before saving the blend to the Database. To open the Property Profile Graph, click the lower half of the Graphs button in the Graphing group of the Home ribbon tab and choose Property Profile Graph from the menu.

   Also, make sure that the Show on Graph icon () is active in the Blend tab in the Navigator pane. The icon is active when surrounded by a light blue box.

   

5. Use the crude

   At any point in your workflow, you can save the crude to the Database by clicking the Save button in the Document group of the Home ribbon tab.

   After the crude has been added to the Database, all of the usual functionality of Assay can be used to analyse and study the crude.