I’m not aware of such a tooling. And I don’t know the grdecl format.
Could it be that there is some confusion of OpenGeoSys (OGS, us) and OpenGoSim (PFLOTRAN-OGS)? At least on the OpenGoSim webpage they mention that format: GRDECL grids — PFLOTRAN documentation. Maybe you should take a look at that page. The two projects are not related at all.