Finding Answers Inside The Box
The Wilson M. Laird Core and Sample Library has a very distinct smell. Inside the 18,000-square-foot drill cutting and core sample storage library, massive shelving units extend two-stories high. The shelves are stacked with cardboard boxes containing rock drilled from the Williston Basin. The smell in the facility is a combination of all that cardboard, of the rocks and the slightest hint of hydrocarbon. Some of the boxes are 50 years old, others are five days. The white labels on every box reveal the Williston Basin’s history, detailing the year a well was drilled and by whom. Julie LeFever, director of the facility for 20-plus years, is proud of the library, of the boxes, even the labels. She can point 20 feet in the air at a shelf of boxes close to the ceiling and tell you where the core samples were taken from and, in most cases, when. She is a career geologist, widely credited with helping the world recognize the potential in the Bakken formation. She is a real-life example of a popular description of those who have combined a lifelong devotion and incredible talent into a singular focus: Julie LeFever has probably forgotten more about the Bakken than most experts will ever know.
Standing with LeFever last month as she pointed out random boxes of interest in the library, it was easy to see that LeFever knows her stuff. She’s become an accomplished organizer as well—a reboxing program was implemented a few years ago and is approaching completion. And, although her story has typically been focused on the past, it was also evident from listening to her that day that LeFever’s role in the future of the Bakken is as important as ever, and the woman sometimes to referred to as Mrs. Bakken has a story of importance that is only just beginning.
A New Understanding
“I think you can see by our facility’s usage that our rocks are important,” she says. “Just about the time we think we have something figured out, we get a new core in and it changes things.”
Operators are required to send drill cutting samples to the library. They also send in core samples. The length of core pre-Bakken drilling days was typically 30 feet. A few years ago the length of core increased to 60 feet and today, Lefever says, cores are coming in at 300 feet. The majority of the cores are from the Bakken, although occasionally cores from the Red River or Tyler formation will show up. Activity on the east flank of the Williston Basin has generated cores from the Madison formation. The cores are now including the lower most Lodgepole formation, Bakken, Three Forks and now well into the BirdBear. “It is a significant expense to core that far, but the information it gives is worth it. “Roughly 8 years into this they are still cutting cores because they still have unanswered questions.”
Some of the cores coming in to the library today, like the BirdBear and the lower Three Forks are giving LeFever access to rock she has never seen before. Supplied with the new rock and a higher volume of Bakken cores, she is gaining an even better understanding of the Williston Basin. She is now going back to work on previous work with a new understanding of the formations. “Changes in the Bakken are pretty subtle, they don’t show up on well logs as much as we’d like them to.”
Some of her work has shown that rock not previously interpreted as reservoir rock is actually just that. “We are using the cores to look at source rocks in deeper formations. The more you know about what the source beds are doing, the more you know about what might be coming down for potential reservoirs for future drilling.” In the Williston Basin, there are 15 active formations that produce hydrocarbons, she said. There is a lot of unknown potential in the formations above and below the Bakken. “You would think that in a basin where we have as many new wells as we do we would know more, but we don’t consider it a very mature basin as far as our knowledge base,” she says. “I anticipate there will be exploration in other units.”
For that to happen, it will take continued research and companies willing to invest in drilling. LeFever calls the Bakken a complex formation because it was once a shallow sea, and minor changes in that sea level affected large areas and made significant changes in the rock.
LeFever is, of course, not the only geologist to utilize the library. During my time there, I shared the lab with a team of five geologists from Whiting Petroleum Corp. Because of bad weather, the team had to drive to Grand Forks from Minneapolis. The lab is one of the main attractions and tools of the facility. Typically, industry teams or academic groups will schedule the lab for a week. Due to the current size of cores, the lab cannot adequately function with more than one group at a time. The team sizes vary from three to seven. On average, the teams will move anywhere from 3,000 feet to 6,000 feet of rock out of the library and into the lab. In 2013, the lab was in use every week of the year minus a few off weeks used for the reboxing efforts.
The building generates a lot of money, and drilling decisions are made based on what a lot of these companies, like Whiting, see in the rock, LeFever says. By 2016, the facility will be at storage capacity. The team in Grand Forks is already working with architects to revamp the building. The team in Grand Forks is already working with architects to revamp the building, and approval of an expansion footprint would have to be made by the Board of Higher Education. The library currently contains 86 percent of the cores cut in North Dakota, a number that would be higher if it weren’t for wells permitted that are never actually drilled.
LeFever is frequently asked to speak or present to other geologists and at industry events, a task she says that still hasn’t stopped her from continuing her work in grasping the truth of the Williston Basin. “The Bakken has changed my life in a positive way.”
The formation won’t produce forever, she says. But, by the time production stops in the Bakken, other formations could offer new opportunities. The play is receiving global attention that is well-deserved. “I think the rocks are key to developing this play,” she says, “I think the Bakken has become, and will remain, very important.”
New Rock Study For Future Production
Stephan Nordeng, a subsurface geologist with the North Dakota Geological Survey, also studies the Bakken. He is currently researching how temperatures, kinetic energy and pressure determine oil generation rates in source bed rocks. Nordeng documented the work in a report, “Building the Science for Advancing Oil and Gas Exploration and Development in the Williston Basin.” Because oil generation rates are related to chemical reactions that occur in organic matter, these studies are focused on defining the relevant physical and chemical properties of the petroleum-generating systems in the Williston Basin, Nordeng said in the report. “These include the chemical properties of the stratigraphic section that controls subsurface temperatures.”
According to Nordeng, petroleum accumulations in the Bakken happen as a result of two processes interacting: organic-rich shales producing petroleum and the ability of the petroleum to flow into the pores of surrounding rocks. Although most traditional oil and gas exploration efforts sought out highly permeable reservoirs (large pores), resource plays such as the Bakken that have low-permeability rates are actually great oil producers. The low-permeability rates require high-pressure outputs by the petroleum flowing into the rock pores, a process that pushes water out of the pores.
“It is the presence of these abnormally high fluid pressures, caused by oil generation and expulsion, that permits substantial oil and, to a lesser degree, gas production to be obtained from the horizontally drilled and hydraulically stimulated reservoirs surrounding the Bakken source rocks,” he said. “Understanding the processes that cause overpressurized reservoirs may provide insights that can be used to explore for other similar petroleum accumulations.”
Author: Luke Geiver
Managing Editor, The Bakken magazine