Abstract: There are obvious differences in the effective production conditions and recoverability evaluation methods between shale oil and gas and conventional oil and gas. In order to investigate the seepage characteristics of shale oil in micro and nano pores, low-velocity seepage experiment was conducted to study the low-velocity non-Darcy seepage patterns of single-phase fluids in Qianjiang Sag, Jiyang Sag and Eagle Ford reservoirs in typical shale blocks at home and abroad. The results of the study showed that the low-rate seepage characteristics of shale oil were mainly affected by the liquid-solid boundary layer effect, slip length and seepage channel. The seepage curve of Qianjiang Sag was concave. The smaller the pressure gradient, the stronger the fluid-solid interface force, and the more obvious the non-linear section; Jiyang Sag was obviously affected by the development of rock core microfractures, and big pores such as inorganic pores and microfractures were the main flow channels at low pressure gradients, with low surface roughness and tortuosity; as the pressure gradient increased, fluid flowed in the small pores and organic pores; Eagle Ford reservoirs were influenced by the mineral composition and pore structure of the block, and the seepage characteristics presented two linear sections with different slopes, and the resistance to seepage increased as the pressure difference increased. The study clarifies the main characteristics and influencing mechanisms of low-velocity seepage of shale oil in nano and micron pores, providing a theoretical basis for formulating shale oil development plans and guiding the efficient development of shale oil.

Key words: shale oil reservoir, low-velocity seepage, single-phase fluid, boundary layer effect, flow resistance