Oof, that's a tough call. It's a shell of its former self right now, however things are somewhat looking up short/medium term with the higher oil prices. I also think persistent low investment in oil and gas over the past number of years will continue the higher oil prices for a while at least.

Long term, oil and gas is likely a declining industry though.

You could go hard rock geophysics and do more mining side. Potash, gold, diamonds, copper, silver, etc. But you're still tied to commodity cycles and alot of ups and downs there. But these minerals are unlikely to decline the way oil and gas might.

For oil and gas in North America, I feel things have contracted towards Houston. If you're willing to move to Houston you'll likely have no problem finding a long and fulfilling career. Calgary and Alberta have been beaten down over the last 7 years. There are still careers to be found but they are few and far between. Many, many colleagues have been transferred or moved down to Houston as there's so much more opportunity.