平台井拉链式压裂套管抗挤能力计算

Calculation of Casing Collapse Strength under Zipper Fracturing in Platform Wells

随着拉链式压裂等新型技术在页岩油气开发中的广泛应用,压裂过程中套管内部承受多级循环内压作用,外部承受由拉链式压裂作业引起的非均匀外挤载荷作用。通过多级循环载荷实验以及数值模拟分析了多级循环载荷以及平台井拉链式压裂套管抗挤强度变化规律,得到了多级压裂套管综合抗挤能力系数计算方法,并应用该计算方法对新疆油田某井区一口套变井进行实例计算。结果表明,在多级循环载荷作用下,套管抗挤强度随循环次数呈线性降低规律;拉链式压裂作业引起井周地应力非均匀分布,套管抗挤强度随地应力非均匀度呈近线性降低趋势;在内外综合作用下,套管抗挤强度降幅超15%,增大了套管变形的风险。提出的平台井拉链式压裂套管抗挤能力计算方法可为现场压裂施工预防套管变形提供一定的计算指导。

With the extensive applications of new technologies such as zipper fracturing in shale oil and gas development,the casing is subjected to both the multi-stage cyclic internal pressure and the external non-uniform compressive load caused by zipper fracturing operations.Given this,this paper analyzes the variation law of casing collpase strength under multi-stage cyclic load and zipper frac-turing of platform wells via the multi-stage cyclic load experiments and numerical simulations.The calculation method of the casing comprehensive collapse strength coefficient under multi-stage fracturing is developed and applied to a casing-deformed well in Xinji-ang Oilfield.The results show that the casing collapse strength decreases linearly with the number of load cycles under cyclic loading.Zipper fracturing results in the non-uniform stress distribution around the well,and the casing collapse strength nearly linearly de-creases with the increasing stress non-uniformity.Under the combined effects of internal and external loads,the casing collapse strength drops by more than 15%,which increases risks of casing deformation.The calculation method of casing callopase strength in platform wells proposed in this paper provides calculation guidance for the prevention of casing deformation in fracturing practice.