During the conduct of the Bureau of Mines vertical borehole methane drainage research program, questions have been raised pertaining to the containment of fractures induced or extended during hydraulic stimulation operations. As a result of these inquiries, a project was initiated in September 1980, to identify the basic parameters controlling induced fracture geometry. Under this effort, 12 vertical boreholes will be completed and subsequently intercepted by mining operations. The boreholes are located at four separate mine sites, with three boreholes planned per mine site. Prior to hydraulic stimulation operations, the in situ stresses will be measured for the coalbed and the rock units immediately above and below it. This information, along with the results of mechanical and frictional properties tests, will be incorporated into the stimulation treatment design. The treatments scheduled for each borehole will allow for variability of injection rate and sand proppant concentration while strictly controlling fluid quality and treatment pressure. Current project plans call for 113m3 (30,000 gal) nitrogen-generated foam treatments and a maximum of 9,000 kg (20,000 lb) of 20-to 40-mesh-size sand proppant. Upon completion of the stimulation treatments, the boreholes will be produced or abandoned depending upon the needs of the mine operators. As borehole interception takes place, underground studies will be performed to delineate the magnitude and orientation of all induced fractures, effects on mining operations, and structural or depositional anomalies in the coalbed and adjacent rock units. These data will be correlated with the treatment design so that adjustments in the design parameters can be made for future treatments. This paper identifies project plans and provides a summary of the activities performed to date.

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