焦石坝地区页岩孔隙连通性及有效性评价

页岩孔隙连通性直接影响油气分子在储层内的运移，从而控制页岩气产出的难易程度，是评价页岩气勘探开发潜力的重要参数之一。以焦石坝地区两口关键井（JYA井和JYB井）五峰组—龙马溪组主力层段页岩为例，开展柱塞样的氦气孔隙度与饱和盐水后的核磁共振孔隙度实验，确定页岩储层孔隙连通性特征，探讨孔隙连通性对页岩气开发的影响。研究结果显示:1）氦气膨胀法主要识别页岩储层中的连通孔隙，而核磁共振法可有效反映样品整体的孔隙空间，两者的比值可量化表征页岩孔隙连通性；2）JYA井氦气孔隙度和核磁孔隙度差异较小，具有强烈的正相关关系，页岩样品整体以连通孔隙为主，连通孔隙占比为69.13%~94.94%，平均为85.12%；3）JYB井页岩孔隙连通性相对较差，连通孔隙占比为36.15%~81.71%，均值为58.19%，仅依靠连通孔隙无法充分反映页岩样品的真实孔隙度，导致氦气孔隙度和核磁孔隙度无明显线性关系。纳米CT三维成像技术模拟的孔隙连通性特征及研究样品的脉冲渗透率差异证实了研究结果的有效性。

Evaluation of Shale Pore Connectivity and Effectiveness in the Jiaoshiba Area,Sichuan Basin

Shale pore connectivity directly affects the migration of oil and gas in a reservoir， thus influencing the level of difficulty in shale gas production. It is an important consideration in the evaluation of exploration and development potential of shale gas. Samples from two key wells （JYA and JYB） in the Jiaoshiba area of the Sichuan Basin were tested by helium porosity of plunger samples and nuclear magnetic resonance （NMR） saturated brine porosity to determine the pore connectivity of shale in the reservoir； the influence of pore connectivity on shale gas development is discussed. The results show that the helium expansion method mainly identifies the connected pores in the shale， while the NMR test reflects the overall pore space of the sample. Thus， the ratio of helium porosity to NMR porosity quantitatively characterizes pore connectivity. Only a small difference was found between helium porosity and NMR porosity in well JYA， and they both have a strong positive correlation， suggesting that the pores are mainly connected （69.13%-94.94%， average 85.12%）. Conversely， the pore connectivity of shale samples from well JYB was relatively poor （about 36.15%-81.71%， average 58.19%）. Therefore， the proportion of connected pores does not fully reflect the true porosity of these samples， and no obvious linear relationship was evident in either the helium porosity or the NMR porosity. These findings were confirmed by nano-computed tomography （nano-CT） and pulse permeability difference tests.