Classic GOM producer still going strong

Mars Gets Mid-Life Boost

When it comes to big finds in the deepwater Gulf of Mexico, the Mars field, in 3,000 feet of water in the Mississippi Canyon Protraction Area, is a true giant.

The field was discovered by Shell Oil Company in 1989 and is owned by operator Shell (71.5 percent) and BP (28.5 percent). In-place volume estimates tally more than four billion BOE.

Mars has produced more than 700 MMBOE to date after first going on production in 1996, and it’s still going strong.

“Mars is sort of a unique basin,” said AAPG member Mike Harris, senior geologist at Shell. “It’s a classic deepwater salt withdrawal mini-basin with 70 individual reservoirs in our plan now, stacked in a 10,000-foot sequence.

“They come from in excess of 50 mapped horizons out here, and what makes Mars so rich is we have this tremendous amount of stacked sands,” Harris noted. “It’s a Plio-Miocene basin, and the majority of that is late Miocene, so we had an incredible accommodation setting here. The hydrocarbons presently reside between 10,000 and 21,000 feet subsea, and they obviously had access to charge.

“All the way down to the deep reservoirs at West Boreas to the shallowest reservoirs at Mars, it represents a sequence that records the history of the development and the fill of the classic deepwater GOM salt withdrawal basin,” he said.

Harris emphasized that one of the absolute unique aspects of Mars is the lack of structural complexity, noting there’s very little faulting in the basin.

Ready for Plan B

The initial development at Mars occurred via the 24-well Tension Leg Platform dubbed Mars A, which garnered some major press when it debuted, boasting production capability of approximately 130,000 BOEPD.

However, production performance exceeded the limits of the TLP, and throughput capacity was doubled.

Mars A has pretty much reached its peak relative to buoyancy and well slot availability given that production surpassed original predictions, and three subsea tiebacks were added along with gas lift and waterflooding capabilities.

Help is on the way.

A whole new 24-well Tension Leg Platform dubbed the Olympus TLP, aka Mars B, is being readied to team with Mars A to provide a combined 48 well slots and over 350,000 BOEPD processing facilities to optimize recovery from the Mars field beyond 2050.

“All of the major contracts have been awarded for the Olympus TLP, which is in the construction phase now,” said Derek Newberry, Mars B business opportunity manager at Shell. “We are targeting first oil from the Mars B in 2015.”

This undertaking is no simple task.

“There are challenges when you try to add infrastructure to a brownfield,” Newberry noted. “You’re immediately challenged with a number of things, such as depleted drilling environments as well as diminished rates because of depletion.

“When we put this development plan together, we had to extract value from the undeveloped reservoirs as well as developed reservoirs in the field,” Newberry said.

“With the advent of the Olympus TLP, which includes 24 slots and a number of additional years of field life, we are including a number of reservoirs that could not be developed from Mars A, and we’re enhancing recovery in the developed reservoirs,” he said.

“We had two to three years of focused effort on understanding these reservoirs and came to the realization that justification is the sum total of everything,” Harris commented.

Newberry noted that another component of adding the additional infrastructure to the basin entails going out to do subsea tieback of some recent exploration discoveries, e.g., West Boreas and South Deimos.

“We matured those discoveries on an accelerated pace with the TLP and have gone from discovery of these fields in 2009 and 2010, respectively, such that we can execute that subsea tieback and bring on production with Mars B in 2015,” Newberry said.

“Mars B is a significant investment,” he added, “and verifies Shell’s commitment and confidence to activity in the Gulf of Mexico.”

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At ACE 2011 ...

Mike Harris will present the paper "Mars Life Cycle Field Development – Maximizing Recovery from a Deepwater Giant" at Evaluation of the Offshore Florida Play Types using Seismic Reflection Data" at 1:20 p.m. Monday, April 11, at the AAPG Annual Convention and Exhibition in Houston.

Co-authors are K. Lambert and Derek Newberry. All are with Shell Oil in New Orleans.

The talk is part of a session titled "E&P in the Americas," a nine-paper program that also includes:

"Fluid Properties Indicated by Natural Gas Isotopes in Gulf of Mexico."

"New Explorations Tramps in the Espino Graben, Eastern Venezuela Basin."

"Geological Setting and Petroleum Potential of the Paleozoic Hudson Platform, Northern Canada."

"The Importance of Upwelling Along the Californian Margin with Links to Sequence Stratigraphy and Petroleum Significance."