During large-scale multistage hydraulic fracturing in shale-gas wells, the cement sheath loses its integrity easily because of repeated temperature and pressure variations in the wellbore. This is likely to form a potential leak path, subsequently leading to the loss of zonal isolation and sustained casing pressure. To prevent such barrier failures, it is crucial to investigate and understand the failure mechanism of cement sheath. In this study, an experimental apparatus and evaluation method of the sealing integrity and mechanical integrity for casing-cement sheath under temperatures and pressures cycle loading have been presented in this paper by which sixteen groups of full-scale integrity tests of general and high-strength cement sheath have been conducted under temperature ranging from 30 to 150 °C and pressure ranging from 0 to 70 MPa cycling loading. The anti-channeling/sealing performance and interface mechanical behavior of casing-cement sheath are measured and characterized respectively under different loading-unloading methods. The cycle numbers required for sealing integrity failure of cement sheath under different cyclic temperatures and pressures have been obtained. The interface mechanical properties (cementing force, friction force, shearing strength and lateral bonding strength) of cement sheath have been obtained, and effects of alternating temperatures and pressures on those mechanical properties and late integrity have been analyzed. Research results can provide a very important reference for the fracturing design of shale-gas wells.

在页岩气井的大规模多阶段水力压裂过程中，由于井眼中温度和压力的反复变化，水泥护套容易失去完整性。这很可能形成潜在的泄漏路径，从而导致区域隔离的丧失和持续的套管压力。为了防止这种屏障破坏，研究和了解水泥护套的破坏机理至关重要。在这个研究中，提出了在温度和压力循环载荷下套管水泥护套密封完整性和机械完整性的实验装置和评价方法，通过该实验设备和评估方法，对十六组普通和高强度水泥护套进行了全面的完整性测试。在30至150°C的温度和0至70 MPa的循环加载压力下进行。在不同的装卸方法下，分别测量和表征了套管水泥护套的抗窜漏/密封性能和界面力学性能。获得了在不同的循环温度和压力下水泥护套的密封完整性破坏所需的循环次数。界面力学性能（固结力，摩擦力，获得了水泥护套的剪切强度和横向粘结强度），并分析了温度和压力的交替变化对那些机械性能和后期完整性的影响。研究结果可为页岩气井压裂设计提供非常重要的参考。