The Qinshui basin covers an area of approximately 42,000 km2 with coal resources and is one of the important regions for coal production and coalbed methane (CBM) exploitation in China. There are two major coalbeds that are important for CBM development. These coalbeds are laminated among sand, shale, and limestone formations and are located approximately from 200 to 1100 m in depth across the basin, with an average thickness between 3 and 6 m. This paper presents a case history of fracture evaluation for a CBM development project in the basin. In this study, fracture growth behavior was evaluated using fracture modeling and microseismic monitoring techniques. The instantaneous shut-in pressure (ISIP) for some treatments in the area of this study was well above the formation overburden stress. Closure stress obtained from diagnostic injection tests was high but lower than the overburden stress. Microseismic mapping results indicated significant fracture complexities, ranging from both confined and excessive height growth to asymmetric fracture growth and multidirectional fracture growth. An abundance of microseisms were detected, but most of them were located in the brittle sand and shale formations below and above the target coalbed. The complex fracture growth is believed to be caused by complex stress regimes and geologic settings in the study area. Fracture closure stress analysis from offset wells confirmed that stress variation was the primary reason for asymmetric fracture growth. Fracture modeling revealed that viscous fluids provided better fracture conductivity in the target coalbed than KCl water, as most proppant would settle below the target coalbed because of the poor transport capacity of water when KCl water was used alone. Based on the results from this study, improvements in fracture treatment design and well spacing should be considered. This paper demonstrates the benefits of an integrated approach to understanding hydraulic fracture growth behavior, which is important for developing a new CBMreservoir.

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