温度作用影响套管抗挤强度的定量评价方法——以页岩气水平井大型压裂施工为例

发布时间：2018-06-09 05:10

本文选题：页岩气 + 水平井　；参考：《天然气工业》2016年04期

【摘要】：目前通常采用大规模水力压裂的方法对页岩气储层进行改造,由于施工排量大、施工时间长,造成井筒温度下降速度快且幅度大,由温度作用而产生的拉应力会降低套管抗挤强度,不利于安全生产。针对页岩气水平井压裂施工工艺及工况条件,建立了水力压裂时的热传导控制方程,并利用有限差分法对其进行求解,分别探讨了不同井口温度下常规水力压裂和大规模水力压裂时井底温度的变化情况;然后再根据API套管挤毁压力计算公式求得了不同钢级套管在不同温度变化时套管抗挤强度的变化值。结果表明:①较之于常规水力压裂,大型水力压裂时,井底温度变化对套管抗挤强度影响较大且对不同钢级的套管抗挤强度的影响程度也有所不同,其中高钢级套管的抗挤强度受影响较小,而低钢级套管抗挤强度受影响则较大;②当在冬季进行施工及水平井垂深更深时,这种由于温度作用造成套管抗挤强度的降低更为明显。结论认为,在对页岩气水平井大规模水力压裂时,必须考虑因为井底温度变化所造成的套管强度降低的问题,并进行合理的套管设计。
[Abstract]:At present, large scale hydraulic fracturing is usually used to reconstruct shale gas reservoir. Because of the large amount of operation discharge and the long construction time, the temperature of wellbore drops quickly and has a large range. The tensile stress caused by temperature will reduce the strength of casing squeezing resistance and be unfavorable to safe production. According to the fracturing technology and working condition of shale gas horizontal well, the heat conduction control equation of hydraulic fracturing is established, and the finite difference method is used to solve the equation. The variation of bottom hole temperature under conventional hydraulic fracturing and large-scale hydraulic fracturing at different wellhead temperatures is discussed respectively. Then according to the formula of API casing collapsing pressure, the variation value of casing collapsing strength of different steel casing at different temperature is obtained. The results show that, compared with conventional hydraulic fracturing, the change of bottom hole temperature has a greater influence on casing anti-squeezing strength and has different influence on casing anti-squeezing strength of different steel grades during large-scale hydraulic fracturing. The high steel casing has less influence on the extrusion strength, while the low steel casing has a greater impact on the squeezing strength when the horizontal well depth is deeper in winter and the construction is carried out in winter, and the vertical depth of the horizontal well is deeper than that of the low steel casing. Because of the temperature effect, the casing collapsing strength decreases more obviously. It is concluded that in large-scale hydraulic fracturing of shale gas horizontal wells, the decrease of casing strength caused by the change of bottom hole temperature must be considered and reasonable casing design should be carried out.
【作者单位】：西南石油大学石油与天然气工程学院;
【基金】：国家科技重大专项“钻井工程设计和工艺软件”(编号:2011ZX05021-006)
【分类号】：TE931.2

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