A multi-layers homologous gas driving water experimental method is established based on fluid flow me-chanics analysis,revealing natural gas flow law in porous rocks and critical mechanical conditions for the formation of water-trapped gas in water-bearing sandstone gas reservoirs.Natural cores from Sulige gas field in Ordos Basin are selected,and parallelly combined based on vertical distribution characteristics of gas well drilled reservoir prop-erties.Homologous stepwised pressurized gas driving water experiments are carried out for completely water-saturat-ed cores.The results show that gas flow path is closely related to reservoir permeability and the pressure of gas driv-ing water.In specific gas driving water pressure conditions,gas flows preferentially through cores with high permea-bility,and gradually covers low-permeability tight cores with stepwised increase of gas driving water pressure.Criti-cal flow pressure difference of gas driving water has good power function relationship with permeability in reservoirs with matrix permeability of<4.77×10-3 μm2,especially those with matrix permeability of≤1.0×10-3 μm2,while in-creases with reservoir permeability decrease.Formation pressure decrease during depletion production of gas reser-voirs cannot break through water trapping resistance,causing water-trapped gas easily formed.The research pro-vides basis for evaluation of remaining gas in reservoirs and recovery improvement through energy replenishing,re-sistance reducing and water-trap removal.
关键词
多孔岩石/天然气/择优渗流/水封气/提高采收率/实验研究
Key words
porous rock/natural gas/preferential flow/water-trapped gas/improve recovery/experimental study
维普
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