关键词: 低渗气藏, 孔隙结构, 物性参数, 渗透率

Abstract: Quantitative relationship betw een pore structure and physical property characteristic of low -pemeability sandstone gas reservoir is studied on the bases of capillary bundle model ,fractal geometry ,surface and colloid chemistry and gas molecule motion theonry. The pore structure features small pore throat rnadius and low height- wide ratio, and much fnactal dimension, big capillary tortuosity and high pore-throat radius ratio. The phy sical property features low permeability, sensitivity to the stress, high capillary pressure and rreducible water saturation, but low initial water saturation, vertically gas- w ater distribution abnomal,coexistence of free molecule flow and viscous flow as well as the high velocity gas flow and low velocity water non-Darcy flow. The given relationship in this paper shows that the efect of various pore structure parameters on some physical property data is not the same. The ffect of pore throat radius on pereability is higher than that on capillary pressure, whereas the effect of fractal dimension on capillary pressure is higher than that on pemeability. The thickness of water film has not afected the effective pore throat size, but affected gas water distribution through altering wettability of rocks and then affected the permeability to gas and water. For very small pore throat in low pereability gas reservoir, the gas molecules assume free flowing, hence either in laboratory or in ield must consider the slippage effect corrections.

Key words: low pemeability gas reservoir, pore structure, physical parameter, permeability