It's been nearly three years since crude last topped the $100-per-barrel mark. For the most part, oil has spent that time selling for less than half that price because of tenacious oversupply. That supply imbalance doesn't appear to be getting any better, because it seems as if shale producers are ramping up output in lockstep with OPEC's reductions.

However, just because the oil market remains saturated with crude right now doesn't mean it will stay that way forever. Here are five potential catalysts that, if more than one were to combine, could turn into rocket fuel and take oil back into the triple digits.

An offshore oil and rig platform at sunrise on a frozen sea.

Image source: Getty Images.

OPEC overshoots

Late last year, OPEC decided it would put a bottom underneath the price of crude -- or so it thought -- by agreeing to cut its combined output by 1.2 million barrels per day for the first six months of 2017. It also sealed a deal with 10 other non-member countries, including Russia, that agreed to cut their supplies by 600,000 barrels per day. However, despite an initial bump, crude prices haven't budged all that much, because rising shale output has mostly filled in the gap. As a result, OPEC is thinking about extending its cuts through the end of 2017, if not longer. By draining more supplies, OPEC is hoping to get market fundamentals back into balance quickly, though it's possible OPEC could overshoot and pull too much oil out of the marketplace and leave spare capacity way too thin.

The decline curve never sleeps

Before OPEC's decision to step in to support the oil market, there was a noticeable decline in worldwide crude supplies because of underinvestment. According to oil industry reservoir specialist Core Labs (NYSE:CLB), by the end of the third quarter of 2016, oil supplies in the U.S. were on pace to fall 11% because of how deeply shale producers slashed investment. Meanwhile, Core Labs noted that output was falling in places such as Angola, Colombia, Mexico, Nigeria, Venezuela, and China for similar reasons. This situation has the potential to grow into a future supply shortage because the industry needs to develop 2.8 million barrels of new production capacity per day just to offset declining and depleting legacy output, which isn't something shale alone can handle at current oil prices. As a result, legacy production could fall to an unsustainable level unless global investment picks up.

Oil workers on a rig. silhouetted against the sky.

Image source: Getty Images.

Wars and rumors of wars

Thanks to the combined efforts of OPEC and underinvestment, the oil market is working its way back into balance. However, that balance could get quickly thrown out of whack in the other direction if something unexpected happens, such as a major terrorist attack or civil unrest in a prominent oil-producing country. There are plenty of hot spots around the globe at the moment, including in OPEC member and leading reserve holder Venezuela, where its retired foreign minister recently warned that the country's protests are spiraling out of control and could lead to civil war. Such an event could potentially knock the country's 2.3 million-barrel-a-day of production offline. Meanwhile, Nigeria has had its share of militant attacks over the years, which could escalate and potentially put it's nearly 2 million-barrel-per-day output out of commission. However, those regions are small potatoes compared with the Persian Gulf, where 17 million barrels of oil flow through the Strait of Hormuz each day. If Iran shuts it down, or if ISIS attacks several key oil terminals in the region at once, it could send the oil market into a frenzy.

The wrath of nature

Another potential supply shock could come from a natural disaster such as a destructive hurricane in the Gulf of Mexico or another devastating wildfire in Canada. For example, when Katrina hit in 2005, it knocked out 95% of the oil production in the Gulf of Mexico, which at the time supplied 1.5 million barrels per day, or about 30% of America's oil. Meanwhile, last year's devastating wildfires in Canada caused about 1 million barrels per day, or a third of its oil output, to go offline. However, in both cases, the market disruption was temporary because neither region suffered a direct hit to its oil infrastructure. But if a future natural disaster does devastating damage to several production facilities or pipelines, it could cause a significant long-term supply disruption.

An oil platform on fire.

Image source: Getty Images.

The sleeping dragon of demand awakes

An unexpected surge in demand is another possible catalyst that could send oil prices skyrocketing, especially if it comes at a time when supplies are already under pressure. Currently, the International Energy Agency expects that oil demand will grow by a healthy 1.3 million barrels per day this year, though that's a slower growth rate than in the past two years, because of weaker demand in Russia and India. However, it's not out of the question that oil demand growth could reaccelerate if global economic conditions improve. Two places to keep an eye on are India and China. While oil demand in India is expected to rise 7% to 8% this year, outpacing Chinese expansion for the third straight year, a reacceleration in China's economic growth rate and faster growth in India could drive its oil demand above expectations. That scenario could provide a significant boost to oil prices if it catches the market flat-footed.

Investor takeaway

Taken in isolation, none these factors alone would be likely to cause crude prices to double anytime soon. However, because OPEC is hard at work to drain supplies at a time when most of the rest of the world has cut back on investing in new output, it's exposing the global market to a potential devastating supply shock. If production from one or more regions unexpected goes offline because of an attack or a natural disaster at the same time there is a surprising acceleration in demand; it could cause crude prices to make their way back toward the triple digits rather quickly. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.