With this .grf the Oil Wells in Temperate (green) terrain no more only decrease, increases are now also possible according to the standard economy formulas (default/smooth (OTTD)).
It's made non-intrusive and shuts itself off in other terrains.

This project provides a GRF build infrastructure for the 32 bit-per-pixel "extra zoom"
graphics that were developed for OpenTTD. The .grf file which this project builds is
suitable for use in OpenTTD versions 1.2.0 and above.

The project builds a single .grf file which contains graphics replacements for the
base-, arctic-, tropical- and extra-sets, and it can be loaded ontop of any graphics
baseset (It has been tested and confirmed to work on top of original_windows,
OpenGFX and zBase)