Research Of Pore Structure And Fluid Mobility In Tight Reservoirs

Based on the comprehensive study of unconventional petroleum accumulations all over the world,the fine recognition and quantitative characterization of micron-nanoscale pores and the evaluation of movable fluids of Chang 7 tight sandstone are achieved by the technology of porosity and permeability test,casting thin sections,QEMSCAN,FE-SEM,Micro-CT,highpressure Hg injection,NMR in Xinanbian area,Ordos Bsain.Combining with regional geological characters about the researched areas,the unfold character of sandstones and the configuration style of sand and mud,the different types of classification methods are put forward and planar distribution of favorable reservoir are predicted in xinanbian area.The major achievements in the thesis are listed below:1.The characters of pore-throst of Chang7 in study area are defined.The lithology of Chang7 reservoir is light-dark grey feldspathic lithic fine sandstone.The reservoir is extremely tight with the plane porosity of 2.05%.The porosity is mainly about 4~10% and the permibility is 0.01~0.3mD.Main types of pores include intergranular pores and felder-intragranular dissolved pores,the ratio of which are 55% and 35%.The next is clay mineral-intergranular pore,which has large quantity and small volume,and the ratio is 5%.The mould pore and mocrorack are seen occasionally,the ratio of which is about 5%.The CT date shows that pores which diameter greater than 2?m make the contribution to total pores less than 20%.The date of high pressure hg injection shows that the dominant diameter of pore throat is within 0.08~0.8?m.2.The characters of movable fluids in study area are determined.The movable fluid saturation is medium~high,the ranges of which is 7.23~57.82% and the average of which is 34.86%.The movable fluid is mainly controlled by the pores within 0.1~1?m.With the increase of reservoir property,movable fluid saturation also increases accordingly,and the percentage of movable fluid which controlled by the larger pore throat slightly increase.3.The different types of classification methods of tight oil reservoir are established.(1)The characters of type?include that prosity is greater than 8%,and the permeabiliy is greater than 0.08 mD.Main types of pores include intergranular pores and felder-intragranular dissolved pores.The dominant radius of pore throat is more than 0.2 ?m.The sands thickness is usually greater than 15 m.The configuration style of sand and mud is given priority to homogeneous-sand model.(2)The characters of type?include that prosity is within 5~8%,and the permeabiliy is within 0.03~0.08 mD.Main types of pores include clay-intergranular pores and felder-intergranular dissolved pores.The dominant radius of pore throat is within 0.1~0.2?m.The sands thickness is usually within 5~15m.The configuration style of sand and mud is given priority to sand-mud-interbed model and sand-mud-gradual change model.(3)The characters of type ? include that prosity is lower than 5%,and the permeabiliy is lower than 0.03 mD.Main types of pores include clay-intergranular pores.The dominant radius of pore throat is lower than 0.1?m.The sands thickness is usually less than 10 m.The configuration style of sand and mud is given priority to sand-mud-gradual change model.