Two things:

1. Geology is a science that's still growing, especially the geology of interpreting seismic data under water. The US has lots of oil off it's south coast in the Gulf of Mexico and north of Alaska. As the geology of finding oil under water improves, there's likely to be more oil found under the Gulf of Mexico and the Arctic Ocean.

2. Also, when you drill a well in an area that's known to contain oil, you typically don't hit just one productive zone, you hit several, each at a different elevation. But, often those other zones will produce gas, and not oil. And, that's a problem for oil companies.

That's because with oil, you can put a pumpjack on that location and pump the oil through a separator into a storage tank. In that case, you use some of the solution gas that comes out of the oil to fuel the engine that runs the pump jack and flare all the rest of the gas. Then you just send out a truck every week or so to collect the oil from the storage tank and transport it to an oil refinery.

But, if you hit gas, then unless there's a gas processing plant nearby, your options are severely limited. Normally the law will require that gas pipelines from gas wells be buried underground, and so crossing someone's farm with a gas line can be expensive, as can crossing a river or a highway. So, when an oil company drills for oil, but only gets gas instead, they typically just shut-in that well until the situation changes, like someone builds a gas plant nearby.

So, the price of oil and the price of gas don't go hand-in hand. That's because as the price of gas goes up, more gas plants get built, and more gas wells come onstream to produce gas to those new plants, thereby tilting the supply and demand balance in the buyer's favour. So, the price of gas is going to rise much more slowly in future than oil did because of all the shut in gas wells all over the place. I expect that just like Alberta, Pennsylvania, Oklahoma and Texas have all kinds of old gas wells that have been shut in for decades because the cost of piping that gas to the nearest gas plant was prohibitive.

All it takes is a small increase in the price of gas for one more gas plant to be built in an area with lots of shut in gas wells, and all of the shut in gas wells in that area suddenly start producing. That's because as long as there's no gas plant in the area, everyone's gas stays in the ground. But, as soon as one well starts producing from a gas reservoir to a gas plant, every other company that has a well penetrating that same reservoir will make tieing their well into the same gas plant a top priority. That's because no one wants to see their gas coming up someone else's well, cuz that means they're stealing YOUR gas.

Alberta has gazillions of shut in gas wells.