The Pore Structure And Flow Characteristics Of Chang4+5Reservoir In Jiyuan Area Of Ordos Basin

Jiyuan area Chang4+5hypotonic-ultra-low permeability reservoir intervals is an important study of the Ordos Basin tight oil. Through core observation, intuitive means of ordinary slice, electron probe, cast sheet, scanning electron microscopy, combined with high pressure Hg (capillary pressure curves) experiments, constant pressure Hg experiment, relative permeability experiments and experimental methods such as nuclear magnetic resonance system on the impact of hypotonic-microscopic pore structure characteristics and mechanism of ultra-low permeability reservoir seepage mechanism reservoir properties were studied and discussed from aspects of deposition and diagenesis its control factors. Mainly get the following understanding:1. Jiyuan area Chang4+5reservoirs are mainly fine lithic arkose, under the influence of lake transgression,thin layer of shale cores visible growth in the core is also visible bituminous vein and thin coal line. Horizontal bedding, cross-bedding, slump structures, convolute bedding, and cracks are well developed;2.Jiyuan area,Chang4+5reservoir diagenesis is diveded into constructive diagenesis and destructive diagenesis.Constructive diagenesis mainly has dissolution of alkali feldspar and kaolinite cementation,followed by chlorite film cementation; The main destructive diagenesis has carbonate cementation and siliceous cemetation. Diagenetic phases include chlorite film cementation-residual intergranular pore phase,feldspar dissolution-residual intergranular pore phase,kaolinite cementation phase, in which feldspar dissolution-residual interguanular pore compared to development, the greatest contuibution of the oil and gas reservoir.3.Experimental high pressure mercury and constant pressure mercury experments show that:The study area complex pore structure, The pore types include residual intergranular pore, dissolved pore, intercrystalline pore etc. The main throat types are lamellar throat and tubular throat, the pore and throat distribution is not uniform,which shows strong heterogeneity. Throat radius is small, with fine throat, micro-fine throat. Microscopic pore structure characteristics of reservoir are mainly affected by the medium pressure and throat radius.4.The oil-water relative permeability and nuclear magnetic resonance experiment have shown:The reservoirs in the study area showed weak hydrophilic wettabiiity, oil-water two phase disturbance is strong, relatively low permeability. The reservoir movable fluid saturation is low, microscopic pore stucture characteristics and diagenesis on reservoir flow characteristics play a major role in controlling.