页岩膨胀对威荣地区套管变形的影响机理研究

威荣地区套管变形问题突出,已成为制约该区块页岩气资源高效开发的瓶颈。通过对现场统计数据的分析,明确威荣地区套管变形与页岩性质及岩性分界面有关。并通过有限元数值模拟对页岩膨胀引起套管变形问题开展分析。研究结果表明:层理缝在液相作用下的层间膨胀导致页岩形变。考虑页岩膨胀应变后的套管外载荷急剧上升。不考虑页岩膨胀应变条件下的岩性分界面对套管外载荷影响有限,考虑页岩膨胀应变后的套管在岩性分界面处的应力集中现象显著增加。密集射孔将释放因页岩膨胀而导致的膨胀应力,是防治威荣地区套管变形问题的有效措施。

Study on the Mechanism of Shale Expansion on Casing Deformation in Weirong Filed

The casing deformation problem in the Weirong area is prominent and has become a bottleneck restricting the efficient development of shale gas resources in this field. It is clear that the casing deformation in the Weirong area is related to the shale properties and lithology interface through the analysis of on-site statistical data. The deformation of casing caused by shale expansion is analyzed according to laboratory experiments and finite element numerical simulation. The results show that the interlayer expansion of the bedding fractures under the action of the liquid phase leads to shale deformation. The caisng stress rises sharply while considering shale expansion. Without considering the shale expansion, the lithology interface has a limited effect on the casing stress. However, the casing stress concentration at the lithology interface increases significantly while considering the shale expansion. Dense perforation will release the swelling stress caused by shale expansion, which is an effective measure to prevent casing deformation in Weirong field.