Study and Application of Cement Slurry for Mitigating Casing Deformation in Shale Gas Well Fracturing
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摘要: 针对川渝地区页岩气储层地质构造复杂、天然裂缝发育导致长水平井密切割压裂中易诱发地层滑移和套管变形的技术难题,提出了一种新型水泥浆体系以缓解套管变形,并开展了现场试验验证。基于地质-工程一体化有限元模拟,系统分析了水泥石弹性模量和变形能力对套管受力的影响,明确了降低弹性模量、提升变形能力的改性方向。通过复合高强变形材料与弹性材料的协同作用,研发的水泥浆体系在保持适度弹性模量(小于5 GPa)的同时,水泥石具备25%以上的变形率,且工程性能满足作业要求。该水泥浆体系在Z-1井成功应用,室内剪切试验显示其套变缓解能力较常规水泥石显著提升,现场压裂施工全程未发生套管变形,证实了其显著的技术效果,为页岩气井全生命周期井筒完整性管理提供了创新解决方案。Abstract: Shale gas reservoirs in the Sichuan-Chongqing area have complex geological structures and well-developed natural fractures, which always result in formation slip and casing deformation in long horizontal section well tight cluster fracturing operation. A new cement slurry system was developed to mitigate casing deformation problem and its performance was verified in field test. Based on the integrated finite element simulation of geology-engineering, the effect of the elastic modulus and deformation capacity of set cement on the casing stress were systematically analyzed, and it was determined to decrease the elastic modulus and to improve the deformation capacity of the set cement. A cement slurry was then developed using highly deformable materials and elastic materials, it has a moderate elastic modulus (< 5 GPa), the set cement has a deformation rate of more than 25%, and its engineering performance satisfies the needs of field operations. This cement slurry was successfully used on the well Z-1. Laboratory shear test results showed that this cement slurry can mitigate casing deformation better than other conventional cement slurries. In field fracturing operation, no casing deformation occurred during the whole operation process, confirming the remarkable technical effect of this cement slurry. The development of this cement slurry provides an innovative solution to the management of wellbore integrity in the whole lifecycle of shale gas wells.
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表 1 套变缓解水泥浆工程性能
ρ/
g/cm3缓凝剂/
%t稠化/min
(70 Bc)流动度/
cm沉降稳定性/
(g/cm3)FL/
mL自由水/
mLp/
MPa1.0 203 21 1.30 2.0 304 22 0.02 35 0 14.5 3.5 569 23 1.0 229 21 1.40 1.5 304 23 0.02 32 0 19.6 3.5 549 22 0.5 228 20 1.50 1.0 295 22 0.01 36 0 21.0 3.5 521 23 表 2 水泥浆性能对比
水泥浆 ρ/
g/cm3弹性
模量/GPap/
MPa水泥石
尺寸轴向
载荷/kN水泥石变
形量/mm变形率/
%实际水泥
环厚度/mm环空双边提供
缓冲位移/mm常规水泥浆 1.90 7.8 21 Φ25.5 mm×49.26 mm 87.36 4.03 8.18 43.5 7.12 套变缓解水泥浆 1.40 3.6 17.9 Φ25.6 mm×50.03 mm 87.36 13.29 28.86 43.5 25.11 注:环空双边提供缓冲位移=实际水泥环厚度×变形率×2;水泥石养护条件为137℃×20.7 MPa×7 d。 -
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