四川盆地页岩气水平井B环空带压原因分析与对策

四川盆地页岩气井环空带压井比例较高，对气藏高效开发和气井井筒完整性带来了挑战。通过对国内页岩气开发区块环空带压实际情况的具体分析，运用同位分析方法确定气体来源，采用物理模拟试验方法开展页岩气井环空带压机理研究，明确了不同水泥浆体系下压裂过程中水泥环密封失效规律，形成了改善水泥环密封性能、缓解分段压裂井环空带压现象的关键技术:在浆柱结构完全满足密封要求的基础上，利用相间填充技术和降低水泥石孔隙度方法，开发出低孔隙度低弹性模量水泥浆体系，弹性模量低至4.2 GPa，相比常规水泥石35%的孔隙度，孔隙度降低27.1%，水泥石弹性变形能力大幅提升。现场5口井的应用实践证明，固井质量优质率达到100%，且未发生环空带压现象，对环空带压的控制具有良好的借鉴作用。

Causal analysis and countermeasures on B sustained casing pressure of shale-gas horizontal wells in the Sichuan Basin

In the Sichuan Basin, the percentage of shale gas wells with sustained casing pressure (SCP) is higher, bringing about the challenges to the efficient development of gas reservoirs and the wellbore integrity of gas wells. In this paper, the actual SCP situations in domestic shale gas development blocks were analyzed specifically. The gas source was determined by using the isotope analysis method, and SCP mechanisms of shale gas wells were studied by means of physical simulation experiment. Accordingly, the failure laws of cement sheath in different cement slurry systems in the process fracturing were fi gured out, and the key technologies to improve the sealing capacity of cement sheath and relieve the SCP phenomenon in staged fracturing wells were developed. When the cement slurry column can structurally satisfy the sealing requirement completely, a cement slurry system of low porosity and Young's modulus was developed by means of the interphase fi lling technique and the set cement porosity decreasing method. Its Young's modulus is only 4.2 GPa, and its porosity is 27.1% (the porosity of conventional cement set 35%). And the elastic deformation capacity of cement set is enhanced dramatically. The new cement slurry system has been practically applied in 5 wells. And its high-quality cementing rate is 100%with no SCP. This research provides the good reference for SCP control.