Just last week, it became apparent that Royal Dutch Shell (NYSE: RDS-A) may finally be getting its affairs in order after years of struggling. Indeed, the company's change became clear enough to me that I cranked out an article describing this new set of circumstances for Fools with a bent for energy investments.

I didn't expect immediate verification of my thoughts, but Shell provided it anyway.

As the week came to a close, the company, along with Canada's Nexen (NYSE: NXY), announced that it had made a "significant" discovery in the U.S. Gulf of Mexico. The find occurred in the Appomattox prospect, which is located in the Gulf's Mississippi Canyon. It therefore joins a string of deepwater finds in what's being called the Golden Triangle, which consists of the deep Lower Tertiary play of the Gulf, along with similarly deep waters off Brazil and West Africa.

The Mississippi Canyon lies in the eastern part of the Gulf of Mexico and therefore remains relatively unexplored. The Shell discovery was drilled in slightly more than 7,000 feet of water to a depth in excess of 25,000 feet below the seabed. It is expected to contain a minimum of 100 million barrels of oil, enough that its development likely will involve its inclusion in a hub with other nearby discoveries by the same partners.

The Appomattox discovery isn't all that Shell has to brag about in the area. It also turns out that the company, with the aid of Statoil (NYSE: STO) and Anadarko (NYSE: APC), has drilled an appraisal well -- delineating 2009's Vito discovery -- which found 600 feet of high-quality oil at a total depth of about 31,000 feet. The well is also in the Mississippi Canyon, and is located nearly a mile from its discovery well. As such, it may indicate that the partners may have tied into a huge field.

Other members of Big Oil -- including BP (NYSE: BP), ExxonMobil (NYSE: XOM), and Chevron (NYSE: CVX) -- are active in the Lower Tertiary. The play is thought to range between 24 million and 65 million years old (or slightly more aged than yours truly).

My feeling is that much of the significance of Shell's successes involves its location in the eastern Gulf, an area that should produce other significant discoveries in the years ahead. As such, I'm happy to repeat my recommendation of last week that Fools watch Shell very, very carefully.

Statoil ASA is a Motley Fool Income Investor selection. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor David Lee Smith doesn't own shares in any of the companies named above. He welcomes your questions or comments. The Fool has a disclosure policy.