Borehole Instability in Malmberget Underground Mine

Borehole instability causes borehole failure, presenting a challenge to the drilling industry (Muller et al. 2009; Zhang 2013). The borehole stability of Marcellus shale wells in long wall mining areas in southeast Pennsylvania, West Virginia, and eastern Ohio has been evaluated by Wang et al. (2014). Here, the ground deformation caused by coal mining generates large ground movement and creates complex stress changes in subsurface rock. This, in turn, triggers interruptions in the operation of the borehole well causing safety and environmental concerns. Borehole walls may fail when the surrounding stress exceeds the tensile, the compressive, or the shear strengths of the rock formation, whichever is reached rst (Zhang et al. 2003). Horizontal well borehole stability is analyzed by the new in situ stress prediction model in shale gas reservoirs (Yuan et al. 2013).