One unconfined compressive strength (UCS) test and four high-pressure triaxial stress tests were conducted on coal cores in order to best emulate the key issues regarding horizontal wellbore stability, coal strength, permeability change, and coal fines generation during the life cycle of a coalbed methane reservoir. The four non-trivial stress paths were: Loading Compression (LC), where the axial stress is increased while the confining stress is held constant; Loading Extension (LE), where the axial stress is held constant while the confining stress is increased; Unloading Compression (ULC), in which the axial stress is held constant while the confining stress is decreased; and Unloading Extension (ULE), during which the confining [...]
