petroleum geology have a future

Doesn't petroleum geology have a future? I'm considering majoring in geology, are there other good paying jobs for them that isn't working with oil companies and teaching? will petroleum geologist still be in demand 20 years from now? is it hard to find a job?

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.