One of the most progressive and technologically savvy tribes in North America, the Southern Ute Indian Tribe (SUIT) has long honored the importance of environmental stewardship while protecting the safety of its members and the community.

ANGEL Services’ aerial photography, DIAL scan patterns, and methane emission plume visualization over a commercial area. (All images courtesy of ITT Corp.)

With tribal lands located in resource-rich southwestern Colorado, the SUIT has also become increasingly sophisticated with its business development activities, and the approximately 1,400 members of the SUIT enjoy financial prosperity due largely to gas reserves.

In fact, coalbed methane (CBM) is the tribe’s most important and marketable natural resource, and its land is populated with wells.

As it has for millennia, a significant quantity of this methane simply seeps out of the ground and is lost to the atmosphere. Over time, this has created a four-fold challenge for the SUIT: (1) a substantial source of potential income is being lost; (2) methane is a potent greenhouse gas; (3) there are potential health and safety issues that could affect people living in areas where methane seepage is occurring; and (4) it kills vegetation by displacing oxygen in the root system.

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Map of the Fruitland Outcrop in Colorado state.

To address these issues, the SUIT first had to identify exactly where the methane seepage was occurring. Identification could be done with hand-held monitoring equipment, but because the methane loss has been occurring over a 90-sq-mile (233-sq-km) outcrop of rugged terrain, this process would have been exceedingly slow, laborious, seasonal, and dangerous.

Instead, the SUIT wanted to try something unprecedented — it wanted to produce a comprehensive CBM seep map over the entire Fruitland Outcrop. To achieve this, the SUIT turned to ITT Corp. and its Airborne Natural Gas Emission Lidar (ANGEL) Services.

Contending with seeps

Another sample of ANGEL Services’ aerial terrain photography and methane plume visualization.

The natural gas loss occurs along the rim of the San Juan Basin in an area known as the Fruitland Formation Outcrop. The Fruitland Formation has long served as one of the largest CBM reservoirs in the world, and the associated gas seeps are occurring along the Fruitland Outcrop both on and off of the SUIT reservation.

“As you produce the methane, you don’t catch all of it with the wells,” said Bill Flint, senior petroleum engineer for the SUIT. “The laws of physics say that the bubble of gas is going to find the point of least resistance, which is at the outcrop. It seeps out into the atmosphere if you don’t do something about it.

“We know there are seeps there because we’ve done ground surveys and seen evidence of dead vegetation, which is caused by methane displacing oxygen around the roots. The challenge is in quantifying that.”

Based upon data from monitoring wells and other surveys, Flint estimates that as much as thousands of cubic feet of methane were being lost on the outcrop.

“We had no way to keep it from getting to the atmosphere,” said Flint. “That is a big number and a significant revenue stream that is being lost. People drill wells for 500 Mcf a day.”

First application in gas exploration

Elevation model showing the ruggedness of the Fruitland Outcrop’s terrain.

To provide a detailed map of the methane seeps, ANGEL Services used a patented, airborne Differential Absorption Lidar (DIAL) laser sensor that detects, images, and maps methane emissions. The DIAL sensor illuminates the ground with mid-wave infrared laser pulses tuned for the detection of methane. The lasers emit 180,000 laser pulses per minute, each of which is scanned across the earth’s surface looking for gas seeps. The concentration of gas in the laser path is calculated by comparing the difference of return laser energy between a reference laser pulse and a laser pulse tuned for methane absorption.

The laser sensor is installed in a Cessna Grand Caravan fixed-wing aircraft that surveys at an altitude of 1,000 ft (305 m) above ground level. In the natural gas industry, the technology is typically used to detect leaks in natural gas pipelines and facilities. Energy pipeline companies in North America used this method to search for leaks in their pipelines, 90% of which are located below ground.

This application of the technology is different from the usual aerial survey process; this is exploration. Exploration of the Fruitland Outcrop was carried out using a grid- or a block-collect in which the plane flies back and forth, precisely overlaying the scan pattern. The scan pattern is 100 ft (31 m) wide, so to do complete coverage of one square mile takes slightly more than 50 passes. The SUIT wanted to identify even minute seeps, making complete coverage the optimal approach.

All of the data from the laser sensor are recorded on electronic media. In addition to the DIAL system, the airplane carries a digital mapping camera to take high-resolution images of the outcrop.

At the end of each mission, the sensor data and imagery are shipped to ANGEL Services’ data processing center in Rochester, N.Y.

“Within a matter of days, our team presented the SUIT with the precise seep locations and color mapping imagery,” said Rick Frisicano, operations and production manager for ANGEL Services. “We delivered geospatial information system-enabled mapping imagery as well as digital global positioning system-encoded datasets. When the lasers detected elevated methane levels on the ground, we precisely placed those seep indications on top of the high-resolution imagery, giving the SUIT’s engineers and scientists the valuable data and locational context they need to make optimal decisions.”

Known seeps confirmed; new ones found

In a fraction of the time needed using previous methods, the mapping done by ANGEL Services has confirmed the ground-based seeps that SUIT scientists had previously identified. It also identified a variety of methane seep locations that the SUIT were previously unaware of.

Flint acknowledges that the data collected by ANGEL Services has proven valuable in a number of areas. “They found a number of seep areas that we didn’t know we had,” he said. “The aerial mapping enabled us to visualize these seeps and plumes for the first time, giving us a unique perspective on what was happening at ground level. There were even instances where our people actually walked a section and did not find any seeps, but actual seeps were discovered through the aerial mapping.

“We’re in a learning curve, but overall I think it has been a very successful way to get an independent nonsurface measurement of what is going on. We now have maps built from the ANGEL Services data that contain exactly the sort of information we were looking for.”

The SUIT engineers also achieved one of their main goals: understanding how much methane was being lost to the air. “During the very first part of the flying, we had a number of monitoring wells that had not been hooked into the gathering system yet and were venting gas into the air,” he said. “These wells had meters on them so we knew the volume that was escaping. They were able to fly a control pass over those wells, and because we could see their signature, we were able to quantify the results.”

The tribe is now using the data to devise plans to capture the lost methane, adding a new revenue stream to their business, helping reduce emissions of greenhouse gases, and protecting the health and safety of people living in the region.