id	keyword
gc-941	shale
gc-941	gas
gc-941	shale gas
gc-941	formation
gc-941	niutitang
gc-941	area
gc-941	content
gc-941	pores
gc-941	formation shale
gc-941	basin
gc-941	reservoir
gc-941	china
gc-941	study
gc-941	fig
gc-941	characteristics