Not much seems more speculative than buying into a privately held oil services company in the Bakken oil patch of western North Dakota. Maybe Las Vegas real estate. Hollywood movies. A nightclub.

And no institutional investor seems more conservative than a Lutheran life insurer.

But MBI Energy Services of Belfield, N.D., is principally owned by a Minneapolis group that includes Thrivent Financial for Lutherans.

If Lutheran life insurers have jumped in, that should remove any remaining suspicions that the Bakken is maybe best left to speculators and opportunists.

This is not a new deal, either. Thrivent and its partners, including the Pohlad organization, invested in MBI two years ago, when many folks were still trying to figure out if the Bakken oil boom had legs. Good move, too, as MBI has since quadrupled in size.

Thrivent's Glen Vanic, a senior managing director, would only allow that he is "optimistic" the MBI investment will turn out well. This for a ball that clearly seems headed out of the park.

Vanic, who manages Thrivent's alternative investment portfolio that includes direct private equity, described a two-year deep dive into the Bakken opportunity, and "we reached the conclusion that the Bakken play is one of the least risky exploration and development plays in the United States."

The Bakken oil patch gets its name from the Bakken formation, a layer of rock roughly 2 miles down that contains the oil. It lies under a wide area of North Dakota, Montana and Canada. The Bakken formation is a thin but contiguous and consistent layer, Vanic said, making the odds of drilling success very predictable. And with newer techniques including the ability to bend a drilling shaft to go straight across the layer of rock, and with a great sweet crude product, the Bakken has, well, boomed.

The most recent Bakken oil production data from North Dakota's Department of Minerals continued to show its steady climb, up to 594,000 barrels per day in June from 320,000 barrels per day in June 2011.

Professional investors are now actively scouting for opportunities among companies active in the Bakken but are "trying to be smart about not investing in flash-in-the-pan opportunities," said Cameron Hewes, a managing director with the investment banking firm of Greene Holcomb & Fisher whose past clients have included a services company active in the Bakken. "A lot of these companies have gone from two guys and a truck to $100 million in revenue in a couple of years. And so, how do you value a business like that compared to a company that has done $100 million for a long time?"

Vanic said Thrivent's bullish conclusion in 2010 coincided with a decision to invest in the first fund of Mill City Capital, a private equity group in Minneapolis. And Mill City had identified a company with an operating history and long-term market presence -- Missouri Basin Well Service, now called MBI.

Mike Israel, the Mill City managing director who is now chairman of the company's board, said MBI was introduced to him by a Minnesota financial adviser. The company's principal owner and CEO, Jim Arthaud, had started it near the peak of the last energy boom, a short-lived run in the early 1980s.

"He survived the ensuing turmoil when a lot of his competitors didn't, and he hunkered down for the next 20 to 25 years," Israel said. "As this started to take off again, [management] said they were as skeptical as anybody. How much do you want to bet on this?"

Israel and his colleagues came to agree with an optimistic take on the long-term potential of Bakken oil production. But part of the appeal of Missouri Basin, renamed MBI Energy Services in 2011, is that it is not a volatile exploration and production company. It is mostly a specialty trucking company, delivering fresh water and other fluids required for drilling and hydrofacturing to well sites, and trucking away water used in drilling and saltwater produced with crude oil. It also hauls oil, drilling mud, tanks and sand.

The Minneapolis investors figured out that MBI's services would be needed long after a well went into production. And what was also attractive about MBI, Israel said, "is this company is a very good actor up there. They have easily the biggest safety and compliance organization in the state of North Dakota, by a big margin."

The deal closed in September 2010. Thrivent and the Pohlad group, investors in Mill City's fund, also invested directly in MBI, as Vanic put it, "helping them write a big enough check."

MBI, growing quickly at the time of the investment, is on track to do about $600 million in revenue this year, Israel said, up from $150 million in 2010. At about 1,500 employees, Israel believes MBI to be the largest for-profit employer in North Dakota.

The new investors have added to their investment since 2010, in part to help fund seven acquisitions, but Israel added that Arthaud remains the largest single shareholder. Israel declined to comment on the amount invested or MBI's profitability, other than to say it has been consistently profitable since his firm invested.

"It's exceeded our expectations," Israel said. "Some things just went our way and we had no control over it. But most significantly is that this management team has done an exceptional job guiding the company through this growth."

lee.schafer@startribune.com • 612-673-4302