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2.0 MINING AND OIL AND GAS DEVELOPMENT <br />- - - -- - <br />2.1 MINING DEVELOPMENT <br />Mining in the area was preceded by the attempted development of the area known as the "second right." This <br />' area is located south of the affected area, and was first developed in January 1988. A geologic anomaly was <br />encountered during development that forced abandonment. <br />' A series of fault location holes were drilled to attempt to locate the magnitude, direction, and extent of the <br />fracture zone. Results of this program did not reveal any faults; however, a structural downwarp, similar to a <br />monocline, was inferred. The monocline appears to decline at a rate of 8 percent to the east over a distance of <br />' 400 feet. The fractured zone was interpreted to trend north-south at 6,600 feet above mean sea level (AMSL). <br />For reference, the surface of the Purgatoire River is at 7,010 feet AMSL, making a fracture zone <br />approximately 410 feet below surface grade at the location of the second ri ght development. Permanent seals <br />' were emplaced to separate the fracture zone from the mine. In addition, vent wells were installed into the <br />second right development, and methane has historically and is currently being extracted from the wells. <br />' After the second right development was abandoned, a development of the mine was turned north under the <br />Purgatoire River. Development of entries under the river began in 1989, and the first longwall panels were <br />mined on the north side of the river in 1993. A ventilation shaft was installed for these activities in late 1989 <br />and early 1990. Mining activities at the site ended in December 1995. <br />' Pumps were deactivated after mining ended and the mine is currently filling with water. In addition, gas is <br />recovered from the mine by active ventilation. The mine is therefore maintained under negative pressure. <br />2.2 NATURAL GAS DEVELOPMENT <br />Gas development at the site has focused on coal bed methane (CBM). CBM is principally extracted from <br />wells installed in coal seams that contain high volumes of gas. The methane is liberated by extracting water <br />from the coal seam via the well, resulting in decreased pore pressure in the coal. Typically, methane is then <br />piped from the wells to compressors, and then to consumers. <br />There are two CBM wells at the site. These wells are known as Picketwire 28-10 and Picketwire 28-11. <br />Picketwire 28-10 is the eastern well and Picketwire 28-11 is the western well (Figure 1). Well 28-10 was <br />spudded on September 24, 1990, and Well 28-11 was spudded on October 25, 1990. <br />Well reports for Well 28-10 indicate that the ground level at the site was 7,018 feet AMSL. The well was first <br />drilled by emplacing a surface casing (conductor) by drilling with a 17-1/2-inch bit to 25 feet, then placing the <br />13 3/8-inch conductor pipe. The conductor pipe was cemented into place, and drilling was commenced with a <br />121 /4-inch bit to 207 feet depth, when the surface conductor washed out and drilling was ceased to recement <br />the conductor. Drilling continued to 448 feet, where an 8 5/8-inch casing was set at 438 feet. Drilling then <br />continued with a 7 7/8-inch bit to 1,550 feet, where a 5 1/2-inch production casing was set. <br />When well 28-10 was drilled, the temperature log indicted that gas was entering the borehole at <br />approximately 504 feet below ground surface (bgs). No circulation to the surface was noted during the 8 5/8- <br />inch casing run. When the 5 1/2-inch casing was cemented, gas was noted flowing between the 8 5/8-inch <br />annulus, gas pressure of 20 to 30 pounds per square inch (psi) was still noted in the annulus between the 8 <br />5/8-inch and 5 1 /2-inch casing. A suspected fault zone was noted at 63- feet. Analysis of the bond log for the <br />casing cement indicates that there is no cement above 450 feet and that the bonding is possibly poor from 450 <br />2006 Methane Monitoring Report (I 1.02.06).doc 2-1