3DSL v2021.0630 on 06/30/21

This is a major new release of 3DSL. Due to the below enhancements, results will not be identical to the previous release version.
Enhancements

1.  Upgraded to SAMG matrix solver 2020.1.
2. The strategy to avoid well layers from backflowing has been changed significantly. See the Section Backflowing Wells.
3. For surveillance forecast runs, wells would sometime have spikes in their phase rates for timesteps where backflow was detected and avoided using the v2021.0407 backflow strategy. The v2021.0630 strategy to avoid backflow layers avoids these spikes.
4. Minor optimizations to streamline tracing and 1D-transport solver.
5. Minor updates to .rst file contents.

Bug Fixes

1. When reading IX or Eclipse runs to extract streamlines, the producer and injector well count was not always updated correctly which caused an exception in studioSL when reading 3DSL’s *.vectors.h5 file.
2. For surveillance forecast runs, wells were not always honoring voidage rates if set on a total voidage rate control.