using the reservoir equation index for the coupling matrix C

[GitPaean]

assemblePerforationEq() now takes the reservoir equation index for the C column in addition to the well equation index. The two coincide for the mass conservation equations, but differ for the energy equation when, e.g., brine is active.

[GitPaean]

jenkins build this please

[Copilot]

Pull request overview

This PR updates perforation equation assembly so the coupling matrix C is indexed by the reservoir equation index (column) rather than implicitly assuming it matches the well equation index. This is necessary because these indices can diverge for the energy equation (e.g., when brine is active), even though they coincide for mass conservation equations.

Changes:

• Extend assemblePerforationEq() (standard + multisegment) to accept an explicit reservoirEqIdx / reservoir_eq_idx.
• Use reservoirEqIdx when writing into eqns.C() to ensure correct coupling-column selection.
• Update multisegment energy perforation assembly to pass Indices::contiEnergyEqIdx for the reservoir-side equation index.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
opm/simulators/wells/StandardWellAssemble.hpp	Adds reservoirEqIdx parameter and documents the well-vs-reservoir index distinction.
opm/simulators/wells/StandardWellAssemble.cpp	Uses reservoirEqIdx for the C-matrix column when assembling perforation Jacobians.
opm/simulators/wells/StandardWell_impl.hpp	Updates perforation assembly call to provide both well and reservoir equation indices.
opm/simulators/wells/MultisegmentWellAssemble.hpp	Adds reservoir_eq_idx parameter and documents the index distinction.
opm/simulators/wells/MultisegmentWellAssemble.cpp	Uses reservoir_eq_idx for the C-matrix column when assembling perforation Jacobians.
opm/simulators/wells/MultisegmentWell_impl.hpp	Updates mass and energy perforation assembly calls to pass the correct reservoir equation index (notably for energy).

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[GitPaean]

It is not an issue at the moment, since MSW does not support brine. It will be an issue when fully-implicit thermal equation for the standard wells be there. Will hold PR as draft to wait for the later development first. Possibly it will go in with other PRs, likely the thermal equation for the standard well.