Quantitative Characterization Of Micro-nanoscale Pore System Of Chang 7 Shale Oil In Ordos Basin

The shale oil of Chang 7 formation in Ordos Basin has complex pore structure which is hard to characterize in nano-micro scale.Conducting pore system research is significant to improve the exploration of shale oil.To study the pore system of shale oil,focused ion beam scanning?FIB?,field emission scanning electron microscopy?FESEM?,N₂ adsorption and mercury intrusion testing?MIP?are employed as main experimental methods.According to experimental results,the type and distribution of pores have been analyzed,the key parameters have been selected to quantitatively characterize full-scale pore system and the influence factors have been revealed.The results showed that the pores is in nano-micro scale and has poor connectivity,lots of scattered,isolated pores can be observed.The main types of pores are intergranular pores,intragranular pores,organic pores,and microfractures.The shale oil of Chang 7 contains a certain amount of macropores.The pore diameter distribution measured by N₂ adsorption is in the range of 1¹00 nm,the curve has a peak at4⁶ nm and another at 50¹00 nm.The pore diameter distribution measured by MIP is in the range of 14.8⁷00 nm,the curve has a peak at 60²40 nm.Full-scale pore system research indicates that the pore diameter of Chang 7 shale oil is in the range of 0¹000nm.The pore diameter distribution curve has the highest peak at 3⁷nm,followed by 20⁶0nm,and the lowest peak at 200⁷00nm,which illustrates micropores are well developed,mesopores are more developed,and macropores are poorly developed.The pore volume of Chang 7 shale oil is between 0.02⁰.26cm³/g,and the surface area is between3.48²1.34m²/g.The volume of micropores,mesopores and macropores accounts for 10.13%,64.95%and 24.92%of the total pore volume.The surface area of micropores,mesopores and macropores accounts for 40.27%,52.30%and 7.43%of the total surface area.Micropores and mesopores are major contributors to surface area of pores,while the macropores can effectively increase the pore volume of shale oil,improve the properties and enhance seepage ability.TOC content and clay minerals promote the development of micropores and mesopores.However,brittle minerals are relevant to macropores and microcracks.