Triangle Petroleum Corp. (NYSE MKT: TPLM), an energy company backed by NGP Energy Capital Management LLC, has begun seeking an adviser for the sale of its oilfield services business, people familiar with the matter said.

Triangle, which in June said it might consider splitting off the business called RockPile Energy Services LLC, is interviewing investment banks to manage the sale, said the people, who asked not to be identified because the matter isn’t public. It might also sell or spin off pipeline operator Caliber Midstream Partners LP after RockPile, one person said.

RockPile, which provides pressure pumping services in the Williston Basin in the Midwestern U.S., generated revenue of about $194 million in the year through January -- including sales to other Triangle units, data compiled by Bloomberg show. The unit has an estimated market value of $572 million, the Denver-based company said in a May presentation, citing the relative value of its publicly-traded peers.

At the time, Triangle had a market value of almost $800 million. Triangle rose 8.4% to $11.08 in New York trading Aug. 4, giving the company a market value of about $954 million. Caliber, the pipeline unit, had an estimated value of $212 million in May, according to the same presentation.

“In my mind, these businesses are not getting full value in the stock,” Triangle's CEO Jon Samuels said on a company earnings call in June, according to a transcript of the call. “Ultimately, it turns back to these businesses standing on their own and being separate.”

Exploration companies have been selling or spinning off oilfield services and pipeline units to focus on oil and gas drilling. By focusing on exploration, they can fetch higher valuations than those involved in multiple businesses. Chesapeake Energy Corp. (NYSE: CHK) spun off its services company, Seventy Seven Energy Inc. (NYSE: SSE), in July.

Since the third quarter of 2012, when RockPile started with 18,000 horsepower (hp) of equipment, the company has steadily grown its fleet of pressure-pumping trucks used to blast water, sand and chemicals underground to release trapped hydrocarbons. It’s expected to have 56,000 hp of gear in the U.S. this quarter and finish the year with 76,000, according to a May 16 report from PacWest Consulting Partners.

Justin Bliffen, Triangle’s CFO, didn’t return phone calls seeking comment on its plans.

Triangle and buyout firm First Reserve Corp. each own half of the general partner of Caliber, which offers water transportation and crude oil and gas-gathering services in the Williston Basin, according to Triangle’s annual report. Its options for divesting Caliber include selling it to another pipeline company, taking it public or spinning it off to shareholders, one person said.

Its exploration arm, Triangle USA Petroleum Co., explores for oil in gas in the Bakken Shale formation.

Natural Gas Partners LLC, the private-equity arm of Irving, Texas-based NGP Energy, controlled a 25% stake in Triangle as of May 2014, including through a convertible note, according to company filings.