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Van Tuyl lecture series: Lessons from uncovering new plays in an old field

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Written by John Bristow

Posted on 08 September 2013

Students who will not have the chance to interact with Dr. Bruce Trudgill during their career at Mines are missing out on an experience. For this past week's Van Tuyl lecture series, the department of geology and geological engineering's own Welsh structural geologist stopped by to give an enthralling lecture in European geography, North Sea oil reserves, and how the school's future can be bettered through paradigm shifts.

For most Van Tuyl lectures, the geology department looks outwards to geologists outside the school to bring a different perspective on geological issues. Given that Trudgill had just returned from his sabbatical year, the lecture served as an amalgamation of original Mines thinking coupled with a novel new approach. Trudgill started off the lecture with a bit of comparative geography. He started off with his normal sense of levity, bringing laughs to the crowd. "Where is Denmark?" he asked with a world map up on the screen, "For a North American audience that could be an important question." After a brief geographic comparison, Trudgill delved into the cultural differences between Colorado and Denmark, a topic that would come up sporadically throughout the lecture. "Days have certain attributes," Trudgill said, "namely a high tolerance for early morning partying," bringing more amused grins out of the audience.

During his time in Denmark, Trudgill worked for Maersk, a company usually known for its shipping division. "Why the hell did you go to work for a shipping company," Trudgill asked himself on behalf of the audience, "aren't you a geologist?" Of course, beyond a few slides showing the largest shipping boat in the world, Trudgill was there to highlight the oil and gas division of Maersk, which is the 18th largest oil and gas company in the world. The company has a broad portfolio of oil and gas development locations worldwide, unfortunately for the company, and luckily for the structural geologist, "they didn't have regional models for a number of key locations." It was Trudgill's job, along with a small army of others to work and define that regional framework.

Since the Van Tuyl lecture is limited by time, Trudgill chose to recount a single story about finding record amounts of oil in a play which was thought to have very little capability for oil and gas development. The focal area for the story was the North Sea Rift Basin, a Triassic and Jurassic period rift off the shore of Denmark. In terms of major oil and gas developments, rift basins comprise around 30 percent of the plays. For the North Sea rift, "there is a significant amount of salt in the system," stated Trudgill. "This can add in a lot of complexity." One of the major focuses of the talk was the increased complexity of the system and how to approach problems in the future. Before the most recent resurgence in developments in the region, according to Trudgill, the mentality had been that "exploration in the North Sea is finished." Recent exploration, on the other hand, has changed how people see the system. While the big companies would not touch the area beyond what they had previously drilled, small companies such as Lundin, a later hero of this story, had taken a radical approach to the area.

Lundin had decided to start searching the area for more oil, originally by working with old data for its portfolio, then by drilling new wells in an attempt to get more data. According to Trudgill, the first two wells failed to find the anticipated Jurassic reservoir, but despite this, they had the shock of finding oil in the porous basement rock. This was a revolutionary surprise that helped unlock the field to more exploration and development. With this discovery, the local governments decided to take the three major companies applying to drill with this new data and placed them in a "forced marriage." Lundin identified a new prospect in 2010, and with a fairly thick pay section, they anticipated around 100-400 million barrels. At this point Trudgill broke into a smile, knowing what was coming, "This was starting to look big." As it turns out, the oil was flowing through the porous basement rock along a glacial induced tilt. On top of all of this, the undiscovered reservoir was more than amazing, "what else makes it work is reservoir quality," revealed Trudgill, "those working in the Piceance Basin and others may want to turn away. When I say good reservoir, I mean [redacted] good reservoir." Trudgill put an image up on the screen of workers pouring oil directly from the rock in the core sample to the audience's amazement. With more work, the estimated reserves were pushed up to around 1700-3300 million barrels. For companies besides Lundin, the announcement served as an eye opener. Companies could no longer get by on basic large models, they need to produce realistic regional models. In regards to taking risks, Trudgill offered this advice, "[if] this is as big of a prospect as it could be, we have to drill it."

The lecture then took a turn to the more current, specifically what it was that Trudgill had done for Maersk. Since there was even more potential for oil and gas in the region and the company did not have the regional models to proceed, it was up to him to interpret the data and produce a better idea of what was going on. Trudgill decided to take a novel approach, and instead of going at it like before,"you have to start from the bottom up, back at the basement and the fabric of that rock." It was also crucial to look through the data for complexity that had been missed originally. One of the structures that Trudgill is particularly versed in that had been missed were the relay ramps. In his opinion, seeing these is good for interpreting the evolution of the system. Many other parts of the original interpretation have changed significantly. Structures such as salt features had been treated like textbook examples, rather than being granted their complexity. "I was taught that the chalk was like a blanket over the central North Sea," said Trudgill reflecting on his original knowledge, which proved to lack the complexity needed for the problem. Even the faults in the system had been over-simplified. One, named the Coffee Sail Fault System, turned out to be many faulting events, not just one.

Trudgill ended the lecture with an appeal to the school, bolstered by elements of his story. For one slide in particular, he put up an image of some work he had done with a high end program called Paleoscan, which builds a stratigraphy and colors it in a way that is readily interpretable. "You put in some tops, let it run, go to the pub, and come back in the morning. It does several months, maybe a year's worth of work overnight." Of course it isn't perfect, but with some direction it is still good. "I got to interpret the most modern information on a big, stonking work station," said Trudgill with a sense of pride. He posited that if there was more emphasis on having good programs and resources like he used, it may have a novel effect on the students at the school and their careers after their education.

On top of an appeal for more high tech equipment, Trudgill also pushed the audience to approach their problems in a more Danish light: to be happier and to work harder.
Colorado School of Mines

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