I'm sure that a jungle planet would probably have more fossil fuels than Earth, as there'd be a lot more organic carbon, which would get buried underground and converted into fossil fuels. We'd probably also need to have factors like tectonic drift, high precipitation, tightly-packed, nonporous soil, etc. in order to bury that organic carbon, and a good amount of heat and pressure. So, the bigger, the better, as larger planets have a greater heat of formation, and more gravity, so there'd be more heat and pressure to turn organic carbon into fossil fuels. What I request for is a formula that predicts how much untapped fossil fuels an planet would have based on factors like:
- Core temperature
And there is a Goldilocks zone, as if the planet's interior has too much heat and pressure, we will get diamonds, and diamonds are not fossil fuels. I hope that that formula can be used to find out how much energy a given planet can store away.