This grid represents the distribution of total dissolved solids (TDS) in the Spirit River hydrostratigraphic unit (HSU). It is a result of a geostatistical model which was constructed using publicly available formation water chemistry data from drillstem tests and production fluids from oil and gas wells.
The TDS distribution was mapped at a regional scale using many years of data, thus providing a good indication of regional water chemistry within the unit rather than site-specific values.
The following statistics describes the accuracy of the geostatistical layer used to create the final grid:
Mean error = -83 mg/L
Root mean square error = 6436 mg/L
Mean standardized error = -0.0092188
Root mean square standardized = 0.97
Average standard error = 6344 mg/L
The root mean square error of the final smoothed grid is 3562 mg/L
The horizontal accuracy of the input TDS point data (AGS DIG 2022-0021), is affected by the locational accuracy of the wells. The locations of the oil and gas wells may be accurate to within millimetres depending on surveying standards at the time of drilling.
The grid was smoothed using focal statistics which calculates for each input cell location a statistic of the values within a specified neighbourhood around it, in this case a 3-cell radius. Smoothing the surface used the average cell value.
Selection criteria and the final data set used for interpolation of this grid are documented in the metadata for AGS DIG 2022-0021.
Step 1 (Modelling the surface): An empirical Bayesian kriging algorithm was used in the ArcMap 10.8.1 Geostatistical Analyst extension to interpolate the TDS values and create a grid of the TDS surface of the Spirit River HSU.
Method Report:
Output surface type: Prediction
Transformation: None
Neighborhood type: Standard circular
Maximum neighbours: 8
Minimum neighbours: 8
Sector type: 4 by 45 degree offset
Samples: 254
Radius: 21 620 m
Cell size: 500 m by 500 m
Step 2 (Grid Smoothing): The grid was smoothed using focal statistics which calculates for each input cell location a statistic of the values within a specified neighbourhood around it, in this case 3-cell radius, smoothing the surface using the average cell value.
Step 3 (Grid Alterations): The final grid was clipped based on the extent of the Spirit River HSU, and spatial distribution of data.