Well model matrices interference with main equations

[FoamScience]

Signs of the bug

• IMPES solver works fine if using an injector well source only, but shows signs of well matrices accounting for boundary conditions of pressure if a BC on water.U is used a flow drive instead of the well.
• When well matrices get instantiated, mesh weirdly stops registering stuff to its objectRegistry.

How to reproduce the bug

• Create wellModel instance before the Mf field and use darcyGradient as the BC Type for p at the inlet.
• Use anything but zeroGradient for the pressure's BC type at the patch adjacent to a well's cell!

Proposed solution

• Maybe find a way to clear well matrices' boundary coeffs (Or better: Never calculate them in the first step).

[FoamScience]

• Fixed The interference of pressure BCs in explicit calculation of well sources by ignoring BC interfaces when calculating A*p