Micro-pore Characteristics Of Shale Reservoirs And Evaluation Of Shale Oil Occurrence And Movability

The microscopic characteristics of reservoir pores and the occurrence and mobility of shale oil are of great significance for evaluating the resource potential of shale oil and the prediction of favorable areas.In this paper,the experimental work of X ray diffraction(XRD),TOC and rock pyrolysis,helium injection,high pressure mercury injection,N₂ adsorption,nuclear magnetic resonance,scanning electron microscopy and atomic force microscopy were carried out for the qn1 member shale samples in the northern Songliao Basin,and conducted Molecular dynamics simulation of shale oil swelling and adsorption.Mainly researched and analysed the pore microscopic characteristics of the shale porosity,pore morphology,pore throat distribution,pore size distribution,pore ratio of different minerals and pore surface roughness,evaluated the shale oil content and the shale oil mobility coefficient of different occurrence states,combined with the grading evaluation of shale reservoirs,predicted the favorable area distribution of shale oil.The pore microscopic characteristics of shale reservoirs were systematically evaluated.The total porosity,pore morphology and pore throat distribution of the shale were obtained by helium gas experiment,N₂ adsorption experiment and high pressure mercury ininjection experiment.An automatic extraction method for SEM pores was established.The T₂ spectral conversion coefficients in NMR experiments were corrected by scanning electron microscopy image pore extraction results to obtain the full-size pore size distribution of shale.Atomic force microscopy experiments were carried out to evaluate the surface roughness coefficient of shale pores.The high-pressure mercury injection experiment combined with the fractal theory divides the pores of the shale reservoir by size into micropores(<10 nm),small holes(10-50 nm),mesopores(50-150 nm)and large pores(>150 nm).According this classification scheme to divide the shale reservoir aperture interval,combined with nuclear magnetic resonance to obtain the full-size pore size distribution of shale to calculate the proportion of micropores,small pores,mesopores and macropores;summarized the porosity of shale reservoirs and the evolution of micropores,small pores,mesopores and macropores with Ro,established the reservoir spatial evolution model of the shale reservoir in the qn1 in the northern Songliao Basin,and combined the quantitative evaluation of different mineral pores to reveal the evolution mechanism of pores during the evolution of mud shale.Molecular dynamics simulation was used to simulate single-component and multi-component shale oil in quartz,kaolinite,graphene and different types of kerogen slit pores.Through the adsorption characteristics of oil in the simulation results,analyzed the effects of pore size,mineral composition,kerogen type,shale oil composition,temperature and pressure on the adsorption of shale oil,and calculated the amount of oil absorbed per unit area of kerogen and mineral.Based on the spherical pore model,combined with porosity,pore size distribution and pore surface roughness coefficient,established the specific surface area evaluation model of mud shale reservoir,and developed different mineral pore identification methods to determine the proportion of pores developed by different minerals,quantitatively evaluated the specific surface area controlled by different minerals in rock reservoirs,and established a quantitative evaluation model of shale oil adsorption.Combined with the parameters of kerogen swelling oil and swelling ratio obtained by molecular dynamics simulation,established a quantitative evaluation model of shale oil in different occurrence states,and clarified the scallop swelling oil quantity,kerogen adsorption oil quantity,kerogen free oil quantity,inorganic mineral adsorption oil quantity and inorganic free oil quantity with Ro evolution law,eventually established the maximum mobility coefficient evaluation model of shale oil to determine the relationship between the shale oil mobility coefficient and shale TOC,mineral content,maturity and porosity.Corrected the heavy hydrocarbons and light hydrocarbons for the shale oil total oil content parameter S₁,and corrected the light hydrocarbons for chloroform bitumen“A”,used the volumetric method to quantitatively evaluate the total shale oil resources of the qn1 Member in the northern Songliao Basin.The TOC and S₁ of the qn1 Member shale in the northern Songliao Basin were evaluated by well logging method to predict the shale oil immobility coefficient of the qn1 Member in the northern Songliao Basin,to evaluate the amount of shale oil movable resources in the qn1 Member in the northern Songliao Basin and predicted the favorable area of movable oil.The grading evaluation criteria of the shale reservoirs in the qn1Member in the northern Songliao Basin is established,and the shale reservoir grading evaluation is carried out to predict the favorable shale reservoirs in the qn1 Member in the northern Songliao Basin.Superimposing the movable oil favorable area and the favorable area of the reservoir,and finally the favorable area of shale oil of qn1 Member in northern Songliao Basin was obtained.