四川页岩气井套管变形特征及受力模式

套管变形是制约四川盆地页岩气高效开发的工程难题。鉴于此,对威远、长宁和昭通区块9口井的37处24臂井径测井数据进行统计学处理,分析了套管变形特征,总结了套管变形类型;结合野外露头、地震和测井数据,分析了页岩岩体结构特征;通过对比套管变形特征及层理页岩岩体裂缝特征,建立了套管与页岩岩体的相互作用模式。研究结果表明:剪切类型的套管变形占60%,呈现剪刀差形态,变形长度(半波长)主要在1.5~2.5 m范围,变形量(波峰)主要在5~15 mm范围;层理页岩被多组裂缝切割为块状岩体,岩体宽度介于1.2~3.1 m;地层与套管相互作用表现为多断块岩体滑动模式。研究结果为进一步定量研究套管受力大小和变形量等提供了依据,也为分析和解决套管变形问题提供了参考。

Deformation Characteristics and Stress Modes of Casings for Shale Gas Wells in Sichuan

Casing deformation is an engineering roadblock curbing the efficient development of shale gas in the Sichuan Basin.In this paper,casing deformation characteristics were analyzed and the casing deformation types were summarized by statistically processing of 24-arm Multi Finger Imaging Tool(MIT-24)log data from 37 locations in 9 wells in the Weiyuan,Changning,Zhaotong blocks.Combined with the outcrop,seismic and log data,the structural characteristics of shale rock mass were analyzed.A casing-rock mass interaction model was established by comparing the casing deformation characteristics and stratified shale rock fracture features.The results showed that:shear deformation accounts for 60% of the total casing deformations,which showing a scissors difference form and has a deformation length(half-wavelength)that is mainly in a range of 1.5~2.5 m and a deformation amount(wave crest)that is mainly in a range of 5~15 mm.Stratified shale rocks are split into massive rocks by multiple fractures,which has a width of 1.2~3.1 m.The casing-formation interaction was shown as multi-fault block rock slide mode.The findings lay a basis for further quantitative researches on casing stress magnitude and casing deformation amount,and offer a reference for analyzing and resolving the casing deformation problems.