因温度、压力变化，海上高温高压井完整性失效事件频发,引发环空带压和井口抬升等问题。基于某高温高压典型井身结构,研制了全尺寸“生产套管—水泥环—技术套管”组合体实验装置,开展了3种不同交变热载荷作用下水泥环界面胶结完整性测试,对比了小尺寸和全尺寸实物实验测试结果差异,明确了交变热载荷作用下水泥环界面胶结衰退行为及机理。结果表明:高温和交变热载荷对水泥环界面胶结性能具有显著的负面影响,失效程度随温度和交变次数的增加而增加。水泥环界面胶结失效之前,交变热载荷作用主要破坏套管与水泥环界面之间的化学粘结作用直至套管—水泥环界面脱离,产生微环隙;微环隙的产生和拓展是导致界面摩擦力降低的主要原因。小尺寸实物实验测试结果与全尺寸实物实验测试结果存在一定差异性,难以准确描述真实工况下的水泥环界面力学性能。研究结果可为高温高压井固井水泥浆设计、井筒完整性管理及井口抬升预测和管理提供依据和参考。

Offshore high-temperature and high-pressure wells frequently experience integrity failures due to changes in temperature and pressure, causing issues such as annular pressure and wellhead uplift. A full-scale “production casing-cement sheath-technical casing” combination experimental device is developed based on the typical wellbore structure of high temperature and high pressure wells. Tests on the cement sheath’s interface bonding integrity were conducted under three different alternating thermal loads, comparing differences between small-scale and full-scale physical experimental results. The study elucidated the degradation behaviour and mechanism of the cement sheath interface bonding under alternating thermal loads. The results show that high temperature and alternating thermal loads have a significant negative impact on the bonding performance of the cement sheath interface, with the degree of failure increasing with higher temperatures and more frequent alternations. Before the bonding failure of the cement sheath interface, the alternating thermal load mainly damages the chemical bonding between the casing and cement sheath interface until detachment occurs, creating micro-annular gaps. The formation and expansion of micro-annular gaps are the main reasons for decreased interfacial friction. There are certain differences between small-scale and full-scale physical experimental results, which make it difficult to accurately describe the mechanical properties of the cement sheath interface under actual conditions. The research findings can provide a basis and reference for the design of cement slurry in well cementing for high-temperature and high-pressure wells, management of wellbore integrity, and prediction and management of wellhead uplift.