Effects of Bedding on Hydraulic Fracturing in Coalbed Methane Reservoirs

Abstract

Bedding is a special structure of coal, which has notable effects on the mechanical parameters of coal and on the hydraulic fracture propagating in coalbed methane reservoirs. To study the effects of bedding on anisotropic characteristics of coal fracture toughness, three-point bending tests have been carried out on raw coal specimens. The results indicate that fracture toughness and failure modes of the specimens both have strong anisotropy due to bedding. A geological geomechanical model of a coalbed methane (CBM) reservoir is built taking into account the effect of bedding to study the hydraulic fracture propagation and the influence of bedding on the fracture network. The hydraulic fracture initiates at the end of the perforation and tends to bifurcate and swerve at the bedding to produce induced fractures. Ultimately, these fractures form a complicated fracture network. The fracture toughness of bedding has great influence on hydraulic fracture geometry. The fracture is likely to bifurcate and swerve at the bedding to form multiple secondary fractures with larger bedding fracture toughness.

Effects of coal bedding dip angle on hydraulic fracturing crack propagation

“…However, the dense nature of coal reservoirs makes the extraction of coalbed methane very restricted, and effective permeability enhancement technology measures are needed to increase the permeability of coal reservoirs. After nearly 70 years of development since the first hydraulic fracturing in the United States, hydraulic fracturing has become an effective technical measure to increase the production of oil, shale gas, natural gas, and coal bed methane (Yu et al 2013;Jiang et al 2017;Wasantha et al 2017;Li et al 2021a, b).…”

Crack initiation and propagation in coalbed gas reservoir during hydraulic fracturing

“…However, the low matrix permeability of coalbed methane reservoir makes it difficult to have natural capacity. So it must rely on the hydraulic fracturing to increase the production to obtain a better capacity [5,6]. The characteristics of physical and mechanical properties on coal rock, the distribution conditions of interlayer, and the construction parameter all have great influence on the hydraulic fracturing effect [7,8].…”