"Infill well” means a well in a compulsory pooled proration or spacing unit to be completed in a pool in which an existing well drilled pursuant to the compulsory pooling order has been completed and not plugged and abandoned.
https://iadclexicon.org/infill-well/#:~:text=“Infill well” m...

“Development well” means a well drilled to a known productive pool.

A development well is drilled in a proven producing area for the production of oil or gas. It stands in contrast to an exploratory well, which is one that is initially drilled to find oil or gas in an unproven area.

https://www.erdoel-erdgas-deutschland.de/erdoel-aus-hessen-r...

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Note added at 8 Stunden (2022-01-21 21:10:37 GMT)
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Infill-Förderbohrungen:
https://www.rohstoff-tv.com/news-magazin/aktueller-stand-der...