Oil drillers in North Dakota's Bakken shale fields are allowing nearly a third of the natural gas they drill to burn off into the air, with a value of more than $100 million per month, according to a study to be released on Monday.

Remote well locations, combined with historically low natural gas prices and the extensive time needed to develop pipeline networks, have fueled the controversial practice, commonly known as flaring. While oil can be stored in tanks indefinitely after drilling, natural gas must be immediately piped to a processing facility.

Flaring has tripled in the past three years, according to the report from Ceres, a nonprofit group that tracks environmental records of public companies.

"There's a lot of shareholder value going up in flames due to flaring," said Ryan Salmon, who wrote the report for Ceres. "Investors want companies to have a more aggressive reaction to flaring and disclose clear steps to fix the problem."

The amount lost to flaring pales in comparison to the $2.21 billion in crude oil production for May in North Dakota.

Still, energy companies are working to build more pipelines and processing facilities to connect many of the state's 9,000 wells - a number expected to hit 50,000 by 2030. But it is a process that takes time and is not always feasible.

"Nobody hates flaring more than the oil operator and the royalty owners," said Ron Ness of the North Dakota Petroleum Council, an industry trade group. "We all understand that the flaring is an economic waste."

Alliance Pipeline is spending about $141 million on a 79-mile pipeline that will carry natural gas from Bakken wells to Alliance's larger interstate pipeline, which cuts through North Dakota from Alberta.

Hess Corp is spending $325 million to more than double its Tioga, North Dakota, processing plant's daily capacity once it opens in October.

Visible From Space

Roughly 29% of natural gas extracted in North Dakota was flared in May, down from an all-time high of 36% in September 2011. But the volume of natural gas produced has nearly tripled in that timeframe to about 900,000 cubic feet per day, boosting flaring in the state to roughly 266,000 million cubic feet per day, according to North Dakota state and Ceres data.

North Dakota's flaring, which NASA astronauts can see from space, releases fewer greenhouse gases than direct emission of natural gas into the air, but it is essentially burning product that could be sold at a profit if there were pipelines.

In Texas and Alaska, which have a well-developed energy infrastructure, less than 1% of natural gas extracted along with oil is burnt off, according to state data.

Oil production remains king in North Dakota, outpacing the amount of natural gas extracted and funding many infrastructure projects. Yet production of natural gas likely will double by 2025, increasing flaring, according to state forecasts.

Drillers have promised to end the practice. Continental Resources, the second-largest Bakken operator with 1.1 million acres under its control, famously declared in March it wants to reduce flaring to "as close to zero % flaring as possible."

Continental says it flares 10.8% of natural gas it produces, and is working with pipeline companies and landowners to cut the number further.

"Internally, it's a front-and-center focus for our company to have wells connected," said Jeff Hume, Continental's vice chairman of strategic growth initiatives. "Everybody makes money when that product is sold, not flared."

The components of natural gas, including low-value methane and lucrative butane, a so-called "natural gas liquid" highly prized by chemical makers, are worth roughly $13 per million cubic feet of natural gas before taxes and transportation fees, at current prices.

With more than 266,000 million cubic feet flared each day in North Dakota, that's roughly $3.6 million in lost revenue, more than $100 million per month.

Roughly 2,300 miles of new pipeline were installed in North Dakota in 2011, the latest year for which data is available. Still, the Bakken spans 18,000 square miles and is the largest oil field in North America.

And about 13% of natural gas flared is at wells that already have pipelines that are too small to handle the high volume of natural gas being drilled, an additional infrastructure problem.

"Everyone's on the same page as far as getting the flaring reduced," said Justin Kringstad, head of the North Dakota Pipeline Authority, a state agency. "It's going to take time to get all the necessary infrastructure built out."