The Study On Seepage Regularity And Imbibition Enhanced Oil Recovery Of Tight Sandstone Reservoir

The permeability of unconventionality-tight-sandstone reservoir is extremely low.The oil reservoirs are buried into deep.Micro-nano pore leads to poor connect ability and it has strong heterogeneity.The control factors of oil and gas seepage law are complex so that the effective utilization of reservoirs is difficult.This article takes a tight sandstone reservoir in an Ordos block as an example,the pore characteristics and micro-percolation mechanism of tight sandstone reservoir are studied by using experimental tests,the article conducted the physical and mathematical model construction and laboratory experiments.Through experimental tests,the pore and permeability parameters of three representative cores in this block are obtained and the casting thin sections are made.The core composition and other physical properties are studied from the microscopic point of view.The capillary force distribution curve and NMR T₂atlas were obtained by high pressure mercury injection and nuclear magnetic resonance respectively.What's more,the atlas were transformed mathematically by integrated the distribution characteristics of core pores and it can be demonstrated by capillary force distribution curve.On the basis of characterizing pore characteristics of unconventionality tight sandstone,a tortuous capillary bundle model coupled with boundary layer effect and fractal characteristics is established.Based on micro-seepage mechanism,three mathematical models of effective permeability model,low-speed non-linear flow model and gas-water relative permeability of tight sandstone reservoirs are derived.The effects of sensitivity parameters on reservoir permeability and non-linear flow characteristics are studied.The characteristics of relative permeability of two-phase flow are analyzed.Finally,the imbibition experiment of unconventionality tight sandstone is carried out,and the multi-factor comparison experiment scheme is designed.The influence of pore and permeability parameters,interfacial tension,salinity of formation water and surfactant on imbibition is explored through the volume method.The research further studies in the main factors that are beneficial to improving the recovery.