Review on formation damage mechanisms and processes in shale gas reservoir: Known and to be known

Producing natural gas from shale gas reservoir presents a great challenge to petroleum industry due to its low permeability nature. The process of gas release and production from shale reservoirs is controlled by the combination of fractures and nano-pore network connected to micrometer pore network. However, the gas production after drill-in, completion and hydraulic fracturing are strongly influenced by formation damage and subsequent decrease of reservoir permeability and fracture conductivity. This paper reviews the main formation damage mechanisms during shale gas reservoir exploitation, including the physical and chemical damage. Formation damage types induced in drill-in, completion and stimulation processes are discussed in detail. Finally, the systematic evaluation method of formation damage, heat treatment and working fluid loss control, as three further research directions for formation damage control and removal are proposed for the efficient development of shale gas reservoirs.