Water reinjection plan gets nodadmin
The Montana Board of Oil and Gas Conservation on Thursday approved two injection wells for a Wyoming-based company that proposes pumping groundwater produced by coal-bed methane drilling back into the ground.
Pinnacle Gas Resources Inc. initially sought permits for four injection wells but said one well got delayed because of weather and, for the time being, it didn’t need the fourth well.
The board’s approval is conditional because Pinnacle’s public notice was two days short of the required 30-day notice. The approval will become final if there are no protests in the next two days. No one protested the wells during Thursday’s hearing at the Petroleum Club in Billings.
Pinnacle, based in Sheridan, is the first natural gas producer to try injecting its coal-bed methane discharge water in the Montana portion of the Powder River Basin. The company also was the first in Montana to treat its water to remove sodium before discharging it into the Tongue River.
The two wells are in addition to three injection wells the board approved in December for Pinnacle. Testing on those three wells went better than hoped and “looks very promising,” said Daniel Arthur, an engineer and managing partner for ALL Consulting, which is working for Pinnacle. ALL was the contractor for the Bureau of Land Management and the state of Montana on the statewide environmental impact statement for coal-bed methane development.
Arthur, who also is a researcher for the U.S. Department of Energy, said the three earlier wells will be converted to monitoring wells and the two new injection wells will be constructed stronger for longer-term use.
The injection wells will allow the company to pump water produced from coal seams 750 feet to 1,200 feet below the surface into a shallower coal seam at a depth between 286 feet and 533 feet. The water will be injected using low pressure.
The shallower coal seam is dry; it contains no water or gas.
Arthur said the coal targeted for water injection is isolated from saturated and gas-bearing coal in the same formation because of faults. The coal seam also is sandwiched between shale, so the water should stay confined to the coal and not interfere with other gas production.
The wells will be drilled on private property, with the water coming from gas wells also drilled on private mineral rights. Drilling the injection wells probably will occur within a month, Arthur said.
Drilling for natural gas found in coal seams requires depressurizing the seam by pumping to the surface huge volumes of groundwater. The groundwater tends to run high in sodium, which can damage plants and soils.
Managing the produced water is one of the biggest issues facing coal-bed methane development in the Powder River Basin, a coal- and gas-rich geological formation that lies in Wyoming and Montana.
Environmental and conservation groups maintain that injecting the groundwater is the best way to manage and conserve the water. Producers generally have not favored reinjection because it can be expensive and difficult to find suitable places.
“We’re still in a learning curve” on reinjection, Arthur told board members. While Arthur said it was too early to know how much water the coal seam could hold, testing information suggests the 20-foot-thick coal seam could hold at least 4.8 million barrels of water under a 640-acre area. A barrel is 42 gallons.
Pinnacle has been studying and evaluating potential areas for water injection for the past two years, said Pete Schoonmaker, president and chief executive officer. The company found a lot of sandstone, which is porous and can accept water. But the sandstone was impermeable and already full of water, he said.
Through its drilling program, Pinnacle found a dry coal seam that was 300 to 400 feet deep. “We really just kind of put two and two together,” he said.
Pinnacle has more than 275,000 acres of mineral interests in the basin. Most of its holdings are in Montana, making Pinnacle one of the state’s biggest players. So far, the company has drilled 160 wells in the Decker area and has 130 wells producing water or water and gas. In Wyoming, Pinnacle has 600 wells producing gas in the Recluse area and last fall was producing, on average, about 18 million cubic feet of gas a day.
Pinnacle will continue to look for other geologic areas that may have dry coal seams, Arthur said. “They’re going to need lots of alternatives for managing their produced water,” he said.
The company is taking an “ultraconservative” approach to the water injection in Montana because it is new and there is not a lot of data, Arthur said.
“We’re really kind of treating this with kid gloves,” he said.
Information from; casperstartribune.net