Mitigation To Date

In 1995, action was taken by the Bureau of Land Management with the support of the Southern Ute Indian Tribe to order the shut-in of five shallow (377’-753’) producing gas wells in Valencia Canyon on the western flank of the Colorado portion of the Basin. These five Fruitland coal wells were converted to pressure monitoring wells by May 31, 1995, and function in that manner to date. (See Appendix C: Chart 21.)

In the Valencia Canyon Area during 1995-1996, previously thriving pinon and juniper trees oriented in a half-mile long by 50-foot wide swath and rooted in the coalbeds had met their demise. Subsequent monitoring results indicated extremely high methane concentration in the soils and a commensurate lack of oxygen required for root health. While no baseline data was available for soil gas in this area, it was deduced that the soil oxygen content necessary to support healthy trees had been recently compromised. An increase in methane micro-seepage had apparently been instrumental in the mortality of the trees over the preceding year as methane gas concentration in the soils overlying coal beds increased, displacing oxygen from the near-surface soils.

In the spring of 1997, a mitigation effort was inaugurated on the Southern Ute Indian Reservation by gas operators having nearby leaseholds and production (Enervest San Juan Operating, LLC, Cedar Ridge, LLC, and Hallwood Petroleum, Inc.). From two well pads located on the coal outcrop and separated by ¼ mile, four boreholes were spudded in the basal coal seams (Figure 10). Directional drilling allowed the boreholes to follow the respective coal seams down-dip. Oriented in a “w” pattern, the boreholes were drilled toward one another at depth. Shallow surface casing was set, with the remainder of the 500-1000 foot length being left open-hole. The intent was to capture methane in the subsurface prior to its migration to the surface. The collected gas was to be gathered for production or flared, depending on the economics.

Figure 10: Slant Wells at Valencia Canyon Gap

The southern pair of slant wells was drilled on a well pad adjacent to a soil gas collector approximately 85 feet long by 10 feet wide that had previously been erected over a segment of the basal coalbeds. This collector documented changes in flow at the outcrop showing steady declines from approximately 25 MCFD when the slant wells were drilled, to approximately 12 MCFD two years later (Appendix C: Chart 22). While this mitigation attempt appears productive, the expenses incurred are considered too great to propose this remedial action on a larger scale. Clearly, other options must be investigated.