ARID Device Economics
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Industry and governmental agencies have known for years that the water quality in the Powder River Basin coals is quite good. In fact, CBM produced water has greatly enhanced livestock operations, through the development of watering areas in previously unused or under-used pastures. In contrast, the water quality of shallow sand aquifers in the same areas is significantly worse than CBM produced water. The shallow sand aquifer system has also been depleted over time due to a lack of recharge through precipitation. The Powder River Basin of Wyoming has been and continues to be in a 15 year drought cycle.

The three principals, through their years of experience dealing with water-related regulatory issues and the oil and gas industry, have developed a disposal process of the produced CBM water and invented the hardware to do the job. They have been getting the thumbs up from industry as well as regulatory agencies as to its merits and have been encouraged to continue the development of their program.

Typical Coal Bed Methane Well

The ARID Process uses the existing well bore to move water from the target coal seam to a shallower depleted aquifer of poorer water quality. This means the production well is also the injection well. The produced water never leaves the well bore as it is redirected into perforations into different aquifer zones. These aquifers are easily identified from the geophysical logs the company runs to confirm the coal zones when the well is first drilled.

ARID Tool -- Water Injection Process

The hardware portion of the ARID Process is a tool which is for the most part a plug which is set above the pumping fluid level of the well and below the receiving aquifer. A water tight well head is placed at the top of the well to trap the water between the tool and the top of the well. Perforations are made into the casing adjacent the receiving aquifer. A pump and water riser pipe are attached to the bottom of the ARID Tool. When the pump is operating, the water is pushed through the ARID Tool and takes the path of least resistance into the receiving aquifer through the perforations

Injection Coal Bed Methane Well

The flow of gas through the ARID Tool is quite simple. As hydraulic head decreases in the coal seam, gas desorbs from the coal seam into a void between the bottom of the ARID Tool and the top of the pumping fluid level. A gas bypass port on the ARID Tool allows the attachment of a 2 3/8 inch gas tubing to the top of the ARID Tool. This port is open through the ARID Tool to the gas which is trapped between the tool and the pumping fluid level. The pipe, full of gas, ascends up through the column of water and out through the water tight well head.

Initial testing has shown the aquifers to be capable of receiving about 75 percent of the water that the aquifer will produce when test pumped. For example, if water from the receiving aquifer could be pumped at 100 Gallons Per Minute (GPM) there is the potential to pump about 75 GPM back into the same receiving aquifer. Bear in mind that a typical CBM well pumps an average of 12 GPM, but pumping rates can range from 0 GPM to 60 GPM.

The ARID Process is permitted by DEQ through an Underground Injection Control (UIC) permit. The DEQ anticipates that the turn around time on a UIC permit application is approximately two to four weeks.

The ARID Process and Tool offers a simple, inexpensive and effective method of water handling offering many advantages, including:
  • No NPDES (National Pollution Discharge Elimination System )permitting required
  • The required UIC (Underground Injection Control) permit is permitted by a less burdened department of DEQ and is typically obtained within two to four weeks of application.
  • The Underground Injection Control permit is included in the cost of the ARID Tool.
  • This process does not involve NEPA (National Environmental Protection Act) or federal mineral regulation.
  • This method would be allowed by the Federal Government to be accounted for in water balance calculations.
  • Wyoming Oil & Gas Conservation Commission will require a Sundry Notice on newly perforated intervals in an existing well, but has no other involvement in the process.
  • Eliminates or greatly reduces Landowner/Attorney negotiations relating to damage payments on water discharge issues.
  • No water flow lines to be constructed to each well.
  • No water outfalls to be constructed.
  • No Discharge Monitor Reports to be completed.
  • Thinner coals become economical as costs of managing produced water are greatly reduced.
  • Wells that produce from 1gpm to 75 gpm or more will be candidates for injection.
  • Environmentally attractive, as better quality water is recharging poorer quality aquifer on which landowners rely.
  • Better economics extend the life of production wells and ultimately the Basin's CBM play.
  • Predictability regarding drilling, construction, and compression allows for better budget planning and forecasting.
  • Maintenance costs for water management facilities are significantly reduced as the ARID Tool has no moving parts and can be re-dressed in the field.

Note: The potential for the ARID Process and Tool in Montana's CBM production is quite extensive as Montana has more coal of a better grade than those found in Wyoming. The regulatory challenges that Montana is facing make the ARID Process and Tool a viable means of development of their CBM resource.