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Effects of Hydraulic Stimulation on Coalbeds and Associated Strata
In studies conducted by the Bureau of Mines, two test areas were hydraulically stimulated and exposed by mining: One in the Pittsburgh coalbed at the Vesta No. 5 mine, Washington County, Pa.; and one in the Illinois No. 6 coalbed at the Inland mine, Jefferson County, Ill. Induced fractures were contained totally within the coalbed with no adverse effect on the stability of associated rock strata. Induced fractures were vertica and were propagated normal to the direction of least residual tectonic stress. Gas production was increased fivefold to twentyfold by hydraulic stimulation. Hydraulic stimulation is a process developed by the oil industry for increasing productivity of a reservoir. Vertical test holes drilled in advance of mining have been hydraulically stimulated to degasify the coalbed more efficiently by increasing the gas flow. The procedure consists of inducing fractures in a coalbed by applying hydraulic pressure with controlled injection of gelled water and propping sand. The fractures are propagated several hundred feet into the coalbed by pumping large volumes of the treatment fluid. Flow characteristics of the fluid and size of propping sand were found to affect the length and width of the induced fracture. Concern for maintaining the integrity of mine roof and floor has deterred coal mine management from applying hydraulic stimulation to increase gas flow from vertical degasification boreholes in advance of mining. This concern motivated the Bureau of Mines to investigate the effects of the stimulation treatment on coalbeds and the rock strata that form the roof and floor of the mine.
Effects of Hydraulic Stimulation on Coalbeds and Associated Strata
In studies conducted by the Bureau of Mines, two test areas were hydraulically stimulated and exposed by mining: One in the Pittsburgh coalbed at the Vesta No. 5 mine, Washington County, Pa.; and one in the Illinois No. 6 coalbed at the Inland mine, Jefferson County, Ill. Induced fractures were contained totally within the coalbed with no adverse effect on the stability of associated rock strata. Induced fractures were vertica and were propagated normal to the direction of least residual tectonic stress. Gas production was increased fivefold to twentyfold by hydraulic stimulation. Hydraulic stimulation is a process developed by the oil industry for increasing productivity of a reservoir. Vertical test holes drilled in advance of mining have been hydraulically stimulated to degasify the coalbed more efficiently by increasing the gas flow. The procedure consists of inducing fractures in a coalbed by applying hydraulic pressure with controlled injection of gelled water and propping sand. The fractures are propagated several hundred feet into the coalbed by pumping large volumes of the treatment fluid. Flow characteristics of the fluid and size of propping sand were found to affect the length and width of the induced fracture. Concern for maintaining the integrity of mine roof and floor has deterred coal mine management from applying hydraulic stimulation to increase gas flow from vertical degasification boreholes in advance of mining. This concern motivated the Bureau of Mines to investigate the effects of the stimulation treatment on coalbeds and the rock strata that form the roof and floor of the mine.
Effects of Hydraulic Stimulation on Coalbeds and Associated Strata
C. H. Elder (author)
1977
28 pages
Report
No indication
English
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