'Educational Gold' in Deepwater GOM Fields

Among the array of not-to-be-missed technical sessions at the upcoming 2017 AAPG Annual Convention and Exhibition (ACE), the Wednesday morning session focusing on major deepwater fields in the Gulf of Mexico is grabbing its share of attention.

“Major Deepwater Fields of the Offshore U.S. Gulf of Mexico” will be co-chaired by AAPG Members Clint Moore and Mark Shuster.

The topic itself signals a significant departure from the industry’s continuing intense focus on onshore unconventional shale plays, where hydrocarbons can be coaxed out of the reservoir far more quickly and inexpensively than in the deep waters in offshore environs.

The Lineup

But how deep is deep, really?

“I tend to think of it as beyond 500 feet, where the shelf drops off steeply, and jackup rigs cannot be used” said Moore, vice president at GulfSlope Energy Inc., which explores the offshore subsalt on the outer shelf and upper slope regions in the Gulf. He noted that some industry participants place the depth at 1,000 feet, but 600 feet is a common number.

This is light years beyond the first commercial offshore oil well drilled in 14 feet of water in the GOM Ship Shoal area off the southeast Louisiana coast.

Image Caption

Perdido is the world’s deepest spar and the second-deepest oil and gas production hub after Shell’s Stones development. Perdido is operated by Shell Oil in the Gulf of Mexico at a depth of about 8,000 feet. Photo courtesy of Shell.

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Among the array of not-to-be-missed technical sessions at the upcoming 2017 AAPG Annual Convention and Exhibition (ACE), the Wednesday morning session focusing on major deepwater fields in the Gulf of Mexico is grabbing its share of attention.

“Major Deepwater Fields of the Offshore U.S. Gulf of Mexico” will be co-chaired by AAPG Members Clint Moore and Mark Shuster.

The topic itself signals a significant departure from the industry’s continuing intense focus on onshore unconventional shale plays, where hydrocarbons can be coaxed out of the reservoir far more quickly and inexpensively than in the deep waters in offshore environs.

The Lineup

But how deep is deep, really?

“I tend to think of it as beyond 500 feet, where the shelf drops off steeply, and jackup rigs cannot be used” said Moore, vice president at GulfSlope Energy Inc., which explores the offshore subsalt on the outer shelf and upper slope regions in the Gulf. He noted that some industry participants place the depth at 1,000 feet, but 600 feet is a common number.

This is light years beyond the first commercial offshore oil well drilled in 14 feet of water in the GOM Ship Shoal area off the southeast Louisiana coast.

Water depth aside, the principle focus of the current action encompasses extraordinarily complicated territory.

It’s subsalt country for the most part, containing many massive horizontal allochthonous salt sheets originating from Jurassic-age salt, often coalescing together. Both high and low pressures, temperatures and permeabilities pose an unending test of industry know-how. Thanks to the sometime multi-mile thick salt sheets, seismic data acquisition, depth image-processing, and interpretation is a challenge all its own.

In contrast, over the course of the first 40 years of offshore GOM exploration, all petroleum reservoir objectives were suprasalt, or above all sheets or beds of salt, explained Moore.

Being a professional geologist with a longtime interest in spreading knowledge of important discoveries to fellow scientists, this is not Moore’s first rodeo.

Among other similarly-themed events in previous years, he organized a daylong session for the 2015 Gulf Coast Association of Geological Societies annual convention, which included 11 deepwater fields.

“Many of my fine colleagues have answered my call to present because they share my excitement to show and see what discoveries look like.” Moore added.

He detailed his rationale for choosing the fields to be presented at the upcoming AAPG annual meeting.

“When I selected these giant and historic fields to be invited to present at this key session,” he said, “I looked at several factors:

  • “Were they exciting and significant geologic stories to tell?
  • “Were they subsalt or salt related?
  • “Could today and tomorrow’s explorers and developers gain critical knowledge from understanding their exploration and development geology?”

Some familiar names made the cut.

“Several of the biggest fields in deepwater GOM history – Perdido, Jack-St. Malo and Thunderhorse – will be presented by their super-major operators,” Moore noted. “And the super-independents will be showing three – Stampede, Lucius and Gunflint – of the most exciting subsalt fields discovered, developed and produced to date in the GOM deepwater.”

The Long View

It’s an impressive picture, but a pertinent consideration is that current offshore action overall remains relatively subdued these days despite oil prices hovering around $54. Personnel layoffs were being announced as recently as early February owing in large part to idled rigs.

Given all of the inherent challenges, the offshore segment of the oil industry is a world unto itself in numerous respects, especially in the deep waters.

The timeline for the major finds in these environments can stretch out as long as a decade from prospect status to production. As a result, such costly efforts must ignore commodity price cycles for the most part. In turn, these long-term projects typically harbor the huge reserves necessary for years-long production once they come online. The U.S. Energy Information Administration recently projected year-end 2017 offshore GOM oil production at 1.9 mmbod, much of which is producing from deepwater fields, like these special six to be showcased in this technical session.

Chevron-operated Jack-St. Malo fields, 280 miles south of New Orleans in the subsalt Lower Tertiary Trend, aptly demonstrate both the extensive timeline for such programs and the important contributions these discoveries can deliver to the domestic supply.

Water depth is 7,000 feet, give or take, and the reservoirs, which are 25 miles apart, lie about five miles below the water surface, according to Chevron. First oil was produced in 2014, yet St. Malo was discovered in 2003 and Jack the following year. The planned production life is 30 years with 500 million barrels of oil tagged to be the expected recovery using current technology.

The two fields are being developed simultaneously with subsea completions flowing back to a semi-submersible floating production host platform sited between them. Electric seafloor pumps boost the produced fluids to the host.

Chevron noted the combined Jack-St. Malo investment, sanctioned in 2010, had an initial development budget of $7.5 billion.

The upcoming opportunity at ACE to listen to an array of operators sharing technical knowledge and experience acquired over the course of discovering such fields and bringing them to the production stage can prove to be invaluable to explorationists and their collaborators.

“Field talks are like educational gold and champagne,” Moore said, “because we all are more successful in finding future fields by knowing what the existing ones look like.”