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When John Harju and his research team are finished working on a $115 million project aimed at modeling the potential of the Three Forks Formation and Middle Bakken benches, the Williston Basin will never be the same. Consider the recoverable oil estimates provided by Harju, Associate Director for Research at the Energy & Environmental Research Center, estimates that could potentially result from the research effort.

“The U.S. Geological Survey has published their new estimates (roughly 7 billion barrels of recoverable oil),” Harju says. “That is a number that as far as we are concerned is in the rearview mirror.”
The conservative nature of the USGS’s estimates combined with emerging technology and constant discoveries in the Bakken have Harju confident that the real number of recoverable oil in the Williston Basin ranges from 30 billion to 50 billion barrels.

For anyone shocked by those numbers, or anyone unconvinced of Harju’s estimations, the names of the exploration and production partners involved in the research assessment combined with EERC’s success with Bakken research, should help ease any concerns that the Bakken oilfield is still getting bigger. Continental Resources Inc., the largest producer in the Bakken, headlines the list of those submitting time, effort and geologic data to EERC for use. As for the institution’s success in the Bakken and how it will play a role in redefining the play, knowing what they know is the best place to start.

The Basics
The simplistic way that Harju and his team think of the Bakken can be described with a reference to a kitchen and a dining room. Conventional resources, unlike the Bakken, are like dining rooms when compared to a kitchen. Harju explains. Unconventional resources are like the kitchen, “that is where oil is made.” In the era of old-technology, prior to today’slong horizontal drilling and multi-stage fracture methods, E&P companies needed to find oil in the dining room.

Conventional resources, or dining rooms, are places with both high rock porosity and high permeability that feature some sort of trap that oil has been captured by. “In essence, the oil has moved into those reservoirs and got stuck,” Harju says. “That was the art of petroleum exploration pre-unconventional.”

The Bakken however, is like the kitchen where oil is made. With the advent of hydraulic fracturing, E&P companies can now research rock formations such as the Williston Basin that feature impermeable, relatively low porosity formations and engineer a reservoir where there wasn’t one. “You are making reservoirs out of source rocks,” he adds, or as the kitchen to dining room analogy goes, E&P companies are turning the
kitchen into the dining room.

The Not-So Basics
While Harju may be able to explain the Bakken Formation and general geology in simple terms of the Williston Basin to anyone willing to listen, his insight on the play can be incredibly complex and valuable to understand the future of the resource. The EERC team has previously worked on water management and water recycling; an effort that Harju explains will help them to develop a new water utilization method that has recently started to work in the Bakken. Previous research by Bethany Kurz, senior research manager, on the play’s water utilization opportunities have given the EERC team a strong base of knowledge for all water-related work. Harju says the team learned current technology isn’t particularly well-suited for flow back or saltwater created during the drilling and production process. Flow back’s tend to be slow in rate and high in salinity.

A typical Bakken flow back will consist of roughly 20 percent salt. As a point of reference, Harju says, seawater is only 3.5 percent salt. If a completion team injects 4 million to5 million gallons of water into a well it might take a year or two to get that water back.

“There is so much capital deployed for so little volumetric treatment opportunity that it poses an economic challenge,” he says.

In addition to the slow return rate and high salinity, a rock formation in western N.D. offers an exceptional saltwater disposal location. “It is an absolutely perfect disposal  zone because it is isolated from the hydrocarbons and it is far below fresh water zones.”

Within the past year however, the EERC team has begun researching the use of saltwater in salt tolerant gels, a practice currently being employed by a handful of production companies. In a typical fracture process, a completion team will use guar gum or another gelling agent to stop the proppant or sand and water mixture from getting stuck in the heel of the well, the portion between the vertical and horizontal casing sections. The guar gum creates a more viscous fluid and keeps the sand in suspension as it travels to the point of the fracture. The new gelling agents can take the place of guar gum, Harju says, and help to recycle flow back water for use in the fracture process. Although research into the new salt tolerant agents is new, Harju expects it to be an area of growth for his team and the Bakken.

In addition to wastewater recycling, the EERC team is also working to establish the best possible approach to enhanced oil recovery (EOR). For the last year, the team has been analyzing and working to test the use of CO2 injected into an oil well as a vehicle to mobilize previously trapped oil droplets, allowing for the recovery of more oil. Currently, the percent of oil recovered in the Bakken resource is roughly 3 to 5%. “If we can change 3 percent to 5 percent to 4 percent to 6 percent,” he says, that is very meaningful. “The denominator on this research is so huge that single type percent increases in recovery are extremely meaningful. A one percent increase of recoverable oil translates to roughly $150 billion of value.”

To find that value, EERC has started to analyze two unsuccessful Bakken EOR pilot projects: one in the Elm Coulee field of Montana and the other in Mountrail County  of North Dakota. The team has arranged a data sharing agreement that will help them better understand the efforts. According to Harju, the EERC team has developed some exciting tests that could help prove Bakken EOR by 2014.

Previous attempts to recover additional oil used a huff and puff method of injection, with very large volumes of CO2 injected into single wells with the hope of mobilizing oil in the vicinity of those wells. The attempts revealed that CO2in the Bakken is very mobile, and according to Harju, it was difficult to retrieve the CO2 and any incremental oil. Previous unsuccessful attempts to prove EOR with CO2 aren’t deterring Harju and the team, however.

Because the rock formations in the Williston Basin are typically oil wet with a thin film of oil covering each tiny granule, the use of water flooding, a process that pushes water through a fractured reservoir to mobilize additional droplets of oil, isn’t an option. Using water, he adds, would only push the oil deeper into the formation. But, CO2 when dissolves into oil it swells, a process that if done correctly, can essentially pop off the unrecovered oil droplets from the tiny granules. “We are very bullish on this.”

The only thing that really competes with EOR in the Bakken is the adoption of refracking practices. To date, Harju says he is only aware of approximately 100 wells have been refracked. Of those, roughly 10 percent have had little success while another 10 percent have shown tremendous success. In the Barnett Shale of Texas, a similar formation  (although primarily a gas field) to that of the Bakken, refracking is highly prevalent, and secondary fracturing operations can yield nearly identical results to initial production. “I think we are very much in the infancy [of Bakken refracking] and design and how to choose the right refrack candidates,” he explains.

“We still have hundreds of wells that haven’t even been fracked once.”

The New Era
Work on saltwater tolerant gels or EOR methodology may have given the EERC team, and the entire Bakken industry, a better understanding of the play, but work on the Three Forks Formation will usher in a new era. Based on initial estimates and data projections on the Three Forks Formation’s potential, a single well pad could house 20 wells: four laterals into the Middle Bakken and four laterals into each discrete bench of the Three Forks.

“This is a big new project that is hugely exciting,” he says. “It is focused on helping to better define the resource.”

The project will also research ways to optimize production methods and provide ways to yield better economics while reducing the environmental footprint of all operations. The play is no longer about finding and securing oil through leases, he says, but rather about finding an orderly way to develop the resource. For the Three Forks Formation work, the end goal is a 3 dimensional model that will be available to the partners in the project and the state. Roughly 65 percent of the funding awarded to the EERC from the state will be used to provide a reservoir characterization model. To do that, the team will use microseismic, geophysical and bore hole logging data. Using geophones, the team will listen to fractures as they are being stimulated to produce new data. The research will last roughly three years and will rely heavily on data logs from Continental Resources, Marathon Oil and Whiting Petroleum Corp. The data compilation project is the first of its kind for the Three Forks Formation, and will also likely include  partners from outside the production industry, and additional oil companies.

“You end up feeling like a very insignificant part of these very large teams,” Harju says. “This is decades and decades of oil and economic vitality to the state. I feel very privileged to be involved with it.”

Luke Geiver, The Bakken magazine