Study consortium being formed

Bakken a Different Breed of Cat

American Association of Petroleum Geologists (AAPG)

‘Midst the plethora of unconventional shale gas resource plays that have sprung up in varying locales across the nation, the emerging Bakken play stands apart as a different breed of cat.

The Bakken, you see, is primarily about oil – the “homegrown” kind.

It’s a Big Deal.

In fact, the U.S. Geological Survey recently announced that its assessment of the Upper Devonian-Lower Mississippian Bakken formation in the Williston Basin in Montana and North Dakota revealed about 3.65 billion barrels of undiscovered technically recoverable oil – the largest single deposit in the United States except for Alaska.

But there’s another reason to call it something different: A special research consortium has been formed to better understand its geology and develop its huge potential.

The consortium effort is spearheaded by two high-profile AAPG members who are the co-principal investigators:

  • Stephen Sonnenberg, a past AAPG president who is now professor and Boettcher chair in petroleum geology at Colorado School of Mines (CSM) and chairman-elect of the House of Delegates.
  • J. Frederick Sarg, an AAPG editor (Memoir 81), past Distinguished Lecturer, past SEPM president and current research professor Colorado Energy Institute at CSM.

Stephen Sonnenberg
Stephen Sonnenberg

J. Frederick Sarg
J. Frederick Sarg
They propose to conduct an initial assessment of the hydrocarbon potential of the Bakken and to develop an integrated reservoir geo-model for this specific stratigraphic interval in the Williston Basin, according to Sonnenberg.

“The Bakken is a world class resource play,” he noted. “To fully understand it will require a big research project, and we hope to aid industry in achieving those technically recoverable numbers.

“The resource assessment we’ll do will include measurements of impedance changes at different Bakken source rock maturity levels,” Sonnenberg said, “using both samples at different measured maturity levels and by measuring properties of samples retorted to different maturity levels.

“The integrated reservoir study will include detailed subsurface mapping of depositional and fracture systems using seismic attributes, core and well logs and sequence stratigraphic analysis,” he continued, “and reservoir characterization using a new high resolution SEM tool to quantify pore systems.”

A Complex Target

Although commonly referred to simply as “a shale,” the Bakken actually is made up of an upper and a lower shale member and a mixed siliciclastic carbonate middle member. The formation reportedly had yielded more than 105 million barrels of produced oil through 2007.

In order to explore and exploit this promising resource to its full potential, however, the consortium leaders see considerable work yet to be done to get a solid handle on the entire Bakken petroleum system comprised of reservoir rocks, organic rich source beds and an abundance of seals.

The various lithologies present are characterized by low porosity and permeability in large part – always a challenge for the operators.

The consortium is being assembled to address the many complex aspects of this apparent huge resource.

It is anticipated that participating companies will provide funding and/or data. The work itself will be performed by students and faculty members.

“We think this will be a two-to-three-year project,” Sonnenberg said. “We’re going to cover all aspects of the Williston Basin Bakken and will start with some early phases of just studying the Elm Coulee area (northeast Montana) and then moving to the Parshall Field area (North Dakota).

“By the end of the study, we will have covered the entire Williston Basin.”

Two student thesis projects already are under way, one focusing on Elm Coulee Field and the other dedicated to Parshall Field.

Objectives and Benefits

Sonnenberg outlined the objectives of the consortium:

  • Characterize geologic, geochemical, geophysical and operational parameters that distinguish the Bakken reservoirs and that differentiate high performing wells.
  • Develop methods to accurately assess the potential of shale and tight reservoirs for oil generation and production using common industry petrophysical measurements.
  • Accurately delineate the natural fracture system to guide horizontal wells to intersect a large number of open fractures.
  • Conduct an initial assessment of the hydrocarbon potential of frontier oil resources.

Industry will benefit from the project in a number of ways, Sonnenberg noted:

  • The study will establish a new predictive framework and geologic model for the Bakken interval that will improve play and prospect assessment and allow a more accurate estimate of reserve volumes.
  • The new predictive geo-model will enhance the operators’ understanding of Bakken producibility, reduce drilling risk and provide more accurate resource estimates.
  • Optimization of drilling and completion strategies will enable companies to improve their cost recovery.
  • Reservoir characterization will optimize reservoir development and reduce the number of drilling locations, yielding a smaller environmental footprint.

“The results of the project will be made public,” Sonnenberg said. “The participants in the consortium will get the immediate results, but eventually all results will be released, including papers, thesis work, dissertations and so on.”

At press time, consortium participants included CSM, Fidelity Exploration, Samson Resources, The Discovery Group and Hendricks and Associates.

Sonnenberg expressed confidence that the effort will attract additional members.

“Talks are in progress that look promising,” he said. “Our main need is to fund students and other expenses we’ll be incurring in this.”

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