Study On Pore Structure And Asphalt Distribution Of Oil Sands In Fengcheng District,northwest Margin Of Junggar Basin

As an unconventional oil and gas resource,oil sands can be an important supplement to conventional oil and gas resources.At present,the domestic and foreign research on oil sand mining and oil sand separation technology is still in the exploratory stage.In order to further improve the efficiency of oil sand extraction and separation,the oil sands of Fengcheng area on the northwest margin of Junggar basin were used as the research object.Firstly,we carried out field investigation,sample collection and basic data collection in the research area.Secondly,the core,rock thin sections and cast thins section of oil sands in the study area were observed,the reservoir development characteristics were analyzed by means of scanning electron microscopy(SEM),X-ray diffracion(XRD)and composition analysis of clay minerals.Finally,the oil sand samples before and after organic solvent extraction were tested by nuclear magnetic resonance(NMR),mercury injection method(MIP),low temperature liquid nitrogen adsorption(LTN₂A)method and other test methods.The pore structure of oil sands is obtained.The different change of pore characteristics before and after oil washing is the distribution of bitumen.By comparing the test data before and after oil washing,the distribution law of bitumen in each pore size in oil sand is summarized.The distribution law of asphalt in oil sands is obtained by comparing the changes before and after.Oil sands in the study area are mainly distributed in the Cretaceous and Jurassic.The lithology of the Cretaceous oil sands consists of sandstone and sandy conglomerate.The upper aparts is sandstone and the low aparts is sandy conglomerate.The oil sands in the Jurassic are mainly sandstone.The oil sands reservoir in the study area has the characteristics of medium-high porosity and medium-high permeability.The oil content of oil sand is mainly distributed between 3%and 16%,the average oil content of 10.5%.The reservoir physical properties are good.The pore types of oil sands in the study area are mainly primary intergranular pores,followed by residual intergranular pores and dissolution pores.There are many types of pore-throat combination in the research area.The heterogeneity of pore throat is strong.There are large hole roars,large hole fine throat,small hole fine throat type hole throat combination.Through low temperature liquid nitrogen associated with high pressure mercury injection token method.The pore capacity of oil sand is mainly distributed at 10?100?m.Specific surface area of stage holes is mainly distributed at micropore-transitional pore and10?100?m.By toluene:alcohol:4:1 mixed organic solvents wash oil sands in different degree of wash oil processing.Using low temperature liquid nitrogen adsorption method,high pressure mercury injection method and nuclear magnetic resonance method,micropore-transitional pore asphalt distribution,micropore-macropore asphalt distribution,micropore-fracture scale asphalt distribution were analyzed.Through low temperature liquid nitrogen associated with high pressure mercury injection token method to analysis oil sands and asphalt in oil sands pore size distribution in the study area.It is concluded that the study area in the oil sands bitumen mainly distribute at 10?100?m macropore,a small amount of micropore,transitional pore and mesopore.By studying the pore structure of oil sands and the occurrence law of asphalt in oil sands in the study area.It provides theoretical basis for the future exploration and development of oil sands.