Re: petroleum geology have a future
Depends what you do within Petroleum Geology, I would say.
Hydrocarbons will remain important as a high energy density, easy to transport fuel for a few decades at least, and then as a chemical feedstock beyond that. The skills related to extracting oil from underground reservoirs are also relevant to things like how aquifers operate and CO2 geo-sequestration (pumping CO2 back underground) which will grow in importance over this time frame.
The most employable skills tend to relate to the most numerate subjects - reservoir engineering and so on; these tend to be the "harder" courses, but the hardest won skills tend to be the most valuable.