Most people who have made maps with well data understand that there are at least 2 different versions of the latitude and longitude well coordinates available – one for the NAD83 datum and one for the NAD27 datum. What’s not always obvious is that in Western Canada, we also have different versions of the township grids as well and this can lead to many more different versions of the well coordinates. For example, we publish 4 different versions for Alberta in the CWD Express PPDM-371 well database. The reason for the different versions is so you can ensure that when well locations are drawn on a map, they can be matched up precisely with the survey grid version used on the map and know that they are in the right place. There can be significant differences between different grid versions and different datum’s and this can lead to incorrectly spotted wells if there is a mismatch between the well spots and the grid.
In Express, we use these tables to store the coordinates:
The WELL table has both bottom and surface coordinates for every well but there is no indication of the grid version or datum.
The WELL_NODE table contains the same set of coordinates that have been “promoted” to the well table along with complete details on the grid version and datum.
The WELL_NODE_VERSION table contains all of the available coordinate versions for every well, including calculated and government supplied coordinates.
To calculate the well coordinates, we use the surveyed township grids and the surveyed well metes and bounds measurements found in the WELL_NODE_M_B table, to precisely spot the surface and bottom well locations. When you combine these with the different geodetic datum’s and include the original coordinates supplied by the government, you can end up with a large number of versions.
To keep track of it all, we use a column named, “ACQUISITION_ID” to identify the source of the coordinates for every row in the WELL_NODE_VERSION table. Here’s a list of the ACQUISITION_ID’s used in the WELL_NODE_VERSION table for the western provinces.
Here is an example query that will return all of the available locations for a specific well in Alberta.
W.UWI = ‘100092908909W500’
AND (W.BASE_NODE_ID = WNV.NODE_ID OR W.SURFACE_NODE_ID = WNV.NODE_ID)
The results are below. The preferred indicator, tells us which row has been promoted to both the WELL_NODE table and the WELL table.
|UWI||NODE OBS NO||NODE POSITION||ACQUISITION_ID||LATITUDE||LONGITUDE||PREFERRED IND|
Here is the complete list of the CWD preferred Acquisition ID’s that are used in the WELL table for each province:
There are cases where we will use the Government supplied versions of the well coordinates for the preferred well node instead of the calculated nodes. The CWD well spot calculator will compare the results of each calculation to check if the LSD and section number resulting from the calculation put the well in the same LSD and section number that are indicated by the well UWI. If they don’t match, then the Government supplied version of the coordinates are marked as the preferred nodes and are promoted to the WELL_NODE table and the WELL table.
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