Checkshots in WDF

Checkshot Surveys in Petrosys Well Data File.

Petrosys Mapping Software v16.7+ can utilize checkshot surveys in the Well Data File (WDF). Here we explain how to import a survey into a WDF and how to use the checkshot survey data in Petrosys. In addition, users will be pleased that well data can now be imported from dbMap and you can copy data more easily between Well Data Files (WDFs).

What is a checkshot survey?

A checkshot survey records time and depth measurements down a borehole and is used to tie the well data (in depth) to the seismic data (in time). A checkshot survey allows the geoscientist to calculate velocity data at discrete well locations. Velocity data derived from checkshot surveys may then be used to perform time to depth conversions.

How to load checkshot surveys into a WDF

Checkshot surveys may be loaded into a Petrosys WDF in two ways. The first method is a bulk load from an ASCII file containing multiple surveys. The second method is to load a survey for a single well. Both methods utilize a checkshot survey saved as an ASCII file and require depth values (MD or TVD) and time measurements (seconds or milliseconds). Step by step importing instructions are available in the Petrosys online help.

‘Define the format’ of importing checkshots into the WDF. Use the /file/import/general option.

Once imported, the data will now be accessible via the Checkshot Survey option in the WDF tree widget or via the checkshot icon (underneath the help menu in image below).

The Checkshot Survey Details Tab (shown below) allows points to be added, deleted or changed. Selecting the Plot tab will enable you to view the data as a depth versus time plot. Once data is imported, the WDF will automatically compute average and interval velocity information.

What can you do with them in Petrosys?

Petrosys has the ability to store a single checkshot survey for each well in the Well Data File (WDF). The data can be loaded, saved, viewed and edited through the Petrosys well editor.

Zone velocity values are computed automatically and can be viewed by adding the velocity attributes to a spreadsheet in the well editor. These velocities can also be used in depth conversion or can be displayed on a map. They can also be displayed as an annotation on the map by modifying the layer displaying the WDF and setting the display parameters under the Zones + Data tab. They may also be used as inputs for gridding operations.

Zone velocity spreadsheet, along with direct posting of velocity information at well location or along well path.

Velocity grids can be used in grid arithmetic to perform time to depth conversions. These can be useful if there is a lack of depth data, but a large amount of seismic data, over the area of interest. You can also use these velocity attributes to create bubble maps representing zone velocity values at discrete locations.

A quick guide to gridding zone velocities

1. From the main Petrosys menu, open Grid, Contour, Volumetrics.
2. Select Grid/Create grid.
3. Select Input data and add Wells/WDF as the data type.
4. Select your WDF and set up the panel (right) to grid one of the zone velocity attributes.
5. Once the input data setup is complete, go back to the main Petrosys gridding control panel and set the output grid name.
6. Set the options on the other panels as required and run the gridding process.

Choose the zone velocity attributes to be used in grid and depth conversion workflows.