Limiting correction to a radius around the well data
Calculate a residual correction without any constraints applied
- To calculate the residual correction:
- Use Create horizon from well markers to create a sparse horizon of your well marker to be tied.
- Use Regrid to resample the sparse marker horizon to a regular grid at your final grid spacing eg 50m
- Use Horizon maths to subtract the sparse horizon from the seismic horizon, the formula is h1-h2.
- Use Interpolate/extrapolate to fill the entire area with the residual correction.
Calculate a template defined by a radius from a well
- To calculate the template:
- Use Horizon maths to modify the regridded (sparse) horizon marker horizon to value 1. The formula is h1/h1.
- Use Create constant horizon to create a horizon value 0 across the area of your final horizon. Use an X/Y spacing similar to or less than your final grid spacing e.g. 50m.
- Use Horizon maths to merge the 2 horizons above together. The formula is merge (h1, h2), ensure the well marker horizon is listed first, h1.
- Use Smooth to create non zero values around the well locations defined by a smoothing radius of your choice e.g. 1500m. If this takes a very long time, consider changing your grid increment in the previous steps.
Note: Create a new horizon each time if you want an audit trail, otherwise replace to update the template and reduce horizons generated.
- Use Horizon maths to cut out the nonzero values. The formula if (h1>0, Nan, h1) should be used.
- Use Horizon maths to merge the 0 template with holes together with the marker horizon value 1. The formula is merge (h1, h2), ensure the well marker horizon is first, h1.
- Use interpolate/extrapolate on the merged horizon to create a smooth transition from value 0 away from the wells to value 1 at the well locations. Make sure the interpolated distance is larger than the radius used during smoothing eg 2000m
- QC the template horizon in the Map View.
- To apply the template to the residual correction, use Horizon maths to multiply the residual correction from part 1 with the template from part 2. The formula is h1*h2.
- To apply the adjusted residual correction to the depth map, use Horizon maths to subtract the adjusted residual correction map from the seismic depth map. The formula is h1 - h2.
- QC work in an arbline that passes through marker location.