From Tax Foundation:

Policies like the tax credit for marginal wells are also classified as subsidies, correctly, as they do provide non-neutral support for the fossil fuel industry.[11]

[11] Josiah Neeley and William Murray, “Bringing Tax Reform to the Energy Sector,” R Street Institute, Policy Study No. 117, November 2017, https://www.rstreet.org/wp-content/uploads/2018/04/117-1.pdf.