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Williston Basin Refracturing Pilot Shows Promise for Older Bakken Wells

A pilot program launched last year between Denver-based Whiting Petroleum Corp. and North Dakota's state-sponsored Oil/Gas Research Council (OGRC) has produced some encouraging results that have Whiting engineers and state energy officials salivating at long-term prospects for boosting oil/natural gas production in the second biggest producing state in the nation.

During a monthly state oil/gas production report on Thursday, Lynn Helms, director of the state’s Department of Mineral Resources (DMR), said the Whiting/OGRC pilot showed significant increases in production and staying-power in the older, pre-2010 wells.

As the Bakken's largest producer, Whiting has many early hydraulic fractured horizontal wells that had "very few stages, if staged at all," said Helms, noting they were in the formative stages of fracking technology that has advanced by leaps and bounds over the past six or seven years. "A lot of these early wells were single-stage frack jobs,” he said.

A year ago, Whiting approached the state research council, part of the North Dakota Industrial Commission - -which also oversees Helms' DMR -- to fund half of a $1.3 million 10-well pilot program. Whiting Oil and Gas Corp. received $600,000 from the council.

Helms has seen the report on the first well in the pilot that applied new technology using coil tubing to add perforations and change the spacing, along with "brand new diverter agents and something called micro proppant for large-volume frack jobs that have become common in the Bakken.” The result was "a five-fold increase in production, and lower gas-oil and water-oil ratios, which means that they absolutely contacted new rock. Not only did the production go way up, but it has stayed that high for months, so there is a lot of excitement around the new technology,” Helms said.

More than 8,000 wells drilled in the Bakken before operators really figured out how to best apply the staging technology, according to Helms. "There are a lot of potential wells that could be done a lot differently without adding anything to the footprint of the oil patch."

Whiting obtained the OGRC support for its "top candidate" -- the Two Shields Butte 14-33-6H well in Dunn County. For months prior to that, Whiting had studied the potential benefits related to refracturing existing horizontal oil wells in the Williston Basin.

Given Whiting's inventory of more than 1,400 pre-2010 wellbores in the Williston, the company stands to realize potential big gains from unlocking additional reserves with the refracking process. Whiting assembled multi-disciplinary teams of geologists, completions engineers, production engineers, reservoir engineers, and landmen to scour seven different areas across the Williston Basin.

The teams evaluated and ranked all the wells, assembling a top-candidates list for the pilot.

In its proposal to the OGRC last year, Whiting made clear that it intended to develop "expertise in the refracturing process and refine certain techniques for both candidate selection and job execution." From this, the company is expecting big payouts in a four-year time period.

A four-phase approach was applied to the refracturing:

  • Well clean-out, casing tests for integrity, and perforation of more holes in the liner;
  • Refracturing the wellbore with 2 million pounds of proppant divided into 26 sub-stages separated by a diversion product that encourages the use of the new perforations to stimulate new parts of the reservoir;
  • Flowback and clean-out of the wellbore; and
  • Monitoring the well for changes in behavior, report the results and evaluate them with a multi-disciplinary team.

In its breakout of the projected $1.3 million cost, proppant accounted for exactly half of that amount at $670,000.

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