页岩油藏单相流体低速渗流特征

Low-velocity Seepage Characteristics of Single-phase Fluid in Shale Reservoir

页岩油气的有效动用条件及可动性评价方式与常规油气相比存在明显差异,为探究页岩油在微纳米孔隙中的渗流特征,采用低速渗流实验对国内外典型页岩区块潜江凹陷、济阳坳陷、美国鹰滩储层单相流体的低速非达西渗流规律进行了研究。研究结果表明:页岩油低速渗流特征主要受液固界面的边界层效应、滑移长度和渗流通道的影响。潜江凹陷渗流曲线呈下凹形特征,压力梯度越小,液固界面作用力越强,非线性段越明显;济阳坳陷受岩心微裂缝发育影响明显,低压力梯度时无机孔、微裂缝等大孔隙是主要流动通道,表面粗糙度及迂曲度低,随压力梯度增大,小孔及有机孔中流体参与流动;鹰滩储层受矿物组成与孔隙结构影响,渗流特征呈现2段斜率不同的线性段,随压差增大渗流阻力增加。该研究明确了微纳米孔隙中页岩油低速渗流的主要特征及影响机制,为制订页岩油开发方案,指导页岩油高效开发提供了理论依据。

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.