| The study area is an important exploration zone in Ordos Basin.In recent years,new discoveries have been made in the Chang 4+5 oil formation of The Triassic Yanchang formation.However,the pore structure controls the reservoir and migration of sandstone gas.So special samples of full system analysis and evaluation is the important foundation of scientific and reasonable and efficient development of reservoir,in accordance with the relevant standards and specifications for the pressure coring analysis tests,pore structure analysis,the casting thin sections identification and determination of rock granularity and capillary pressure curve,X-ray diffraction,scanning electron microscopy(sem)analysis and cathode luminescent thin section identification,oil displacement efficiency,oil and water relative permeability,measurement of wettability,core sensitivity evaluation analysis experiment,petrological characteristics and pore structure characteristics are studied,and the influence factors of reservoir physical properties.The petrology,physical property and pore structure of the reservoir show that the chang4+5 oil formation is mainly feldspar-porphyry sandstone,mainly fine sandstone,with good sorting,sub-rhomboid degree of roundness and high maturity.The pore type shows the development of intergranular pore,which belongs to the low-ultra-low permeability reservoir,and has the characteristics of small pore throat and complex structure.The porosity range of long 4+5 reservoir was 1.68%?19.99%by physical property analysis,and the average value was 12.07%.The permeability range is 0.0141×10-3?m2?7.98×10-3?m2,with an average value of 1.05×10-3?m2.Average oil saturation is 42.92%;Average water saturation is 55.77%.The capillary pressure curve was measured for the samples with a length of 4+5 oil layer.The test results showed that the displacement pressure range was 0.069?23.988MPa,with an average of 2.77MPa.The median pressure range is 0.832?44.604MPa.The physical properties of Chang4+5 reservoirs are mainly affected by sedimentation and diagenesis,and the horizontal distribution of reservoirs is controlled by sedimentary facies belts.Different sand bodies are formed in different sedimentary environments,and these sand bodies have different characteristics in composition,grain size,sorting property,rounding,impurity content and distribution law,etc.Therefore,the original pore and permeability characteristics of the sand bodies in reservoirs are also different.The second is diagenesis.The diagenesis of chang4+5 reservoir sandstone in the study area is diverse,and diagenesis affects the reservoir physical property of the sandstone in the study area to a large extent.The main diagenesis types in the study area are mechanical compaction,cementation and dissolution,etc.,which can be divided into destructive and constructive diagenesis.Thus,the favorable aspects of reservoir physical property can be analyzed and studied. |
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