OPEC's failure to increase output has raised speculation as to whether worldwide supply can meet future demand. Many believe OPEC won't increase output because it can't, and if that's true, where will future supply come from?

Black gold rush
ExxonMobil (NYSE: XOM) recently reported the largest discovery in the Gulf of Mexico in the last decade. The company estimates the wells hold approximately 700 million barrels of oil. That's a 35-day oil supply based on current U.S. consumption rates.   

Royal Dutch Shell is launching development on a sizable discovery in the Gulf. Last year, the company discovered an oil field capable of producing approximately 140 million barrels over its lifetime. Based on current consumption of roughly 20 million barrels a day, the Shell discovery is enough oil to meet U.S. demand for approximately seven days.

Surprisingly, ATP Oil & Gas (Nasdaq: ATPG) is one of the most active drillers in the Gulf. The company ranks fourth in deepwater Gulf of Mexico wellbores and in total, holds 144 million barrels of oil reserves in the region.  

All told, the Gulf of Mexico is estimated to hold 45 billion barrels in recoverable reserves. Drilling activity is picking up again after the temporary halt in production in the wake of the BP oil spill. But the hunt for oil doesn't stop in the Gulf.

There are numerous onshore supply sources as well. The Eagle Ford shale in Texas is chief among these. EOG Resources is a big player in the fertile oil field. The company reportedly has 900 million barrels of oil in the region.

Marathon Oil (NYSE: MRO) sees potential in the shale as well. The company recently shelled out $3.5 billion to double its land position in the region. Marathon now holds a top five acreage position in the promising oil field.

Chinese oil giant CNOOC is betting big on the Eagle Ford shale. Late last year, the company paid Chesapeake Energy (NYSE: CHK) $1.1 billion for 30% of Chesapeake's acreage in the oil field.

All told, some project the Eagle Ford shale holds about 25 billion barrels of oil, making it the most significant recent oil discovery in the United States. 

Another significant discovery is the Bakken shale in North Dakota. The United States Geological Survey estimates the recoverable reserves at 24 billion barrels in the region.

Continental Resources (NYSE: CLR) is the top producer in the Bakken and is expected to triple production in the region over the next three years. Continental has high hopes for the future. The company is setting a growth goal of 300% over the next five years.

Kodiak Oil and Gas (AMEX: KOG) is another explorer targeting the Bakken. Kodiak recently acquired 25,000 acres in the Bakken, increasing its net acreage position to 95,000.  

Then there's the highly debated Arctic National Wildlife Refuge. It's hard to predict how much oil the region contains, but the mean estimate of geologists places the figure at 10.4 billion barrels of recoverable reserves.

That's a lot of oil, but the problem is many believe it would take several years and a significant financial commitment before we experience the benefit from exploring the wildlife refuge.

Last year, ConocoPhillips (NYSE: COP) pulled out of Alaska claiming that investing in the region is not competitive with other exploration projects. However, expect ANWR exploration talks to heat up again with oil prices on the rise.

Below is a table summarizing the potential impact of some highly targeted oil fields based on current U.S. consumption rate of 25 million barrels a day.


Estimated recoverable reserves

Potential U.S. Supply (years)

Gulf of Mexico 45 billion barrels 6
Eagle Ford shale 25 billion barrels 3
Bakken shale 24 billion barrels 3
ANWR 10 billion barrels 1

The bottom line
All of these oil fields could partially pick up the slack for OPEC. But keeping up with U.S. as well as soaring worldwide demand will become increasingly difficult.

Investors should look to add some black gold to their portfolio, as the economics favors companies exploring for this valuable commodity. With situations like this in mind, The Motley Fool has created a new special oil report titled "3 Stocks for $100 Oil," which you can download today, absolutely free. In this report, Fool analysts cover three outstanding oil companies, including the stock Fool analyst David Lee Smith calls the "energy king." To get instant access to the names of the three oil stocks, click here -- it's free.

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.