环空圈闭压力对水泥环密封失效的影响

针对深水高温高压井环空圈闭压力变化可能造成水泥环密封失效的问题,现有文献大多从现场管理措施及理论模型的角度进行研究。鉴于此,基于全尺寸水泥环密封完整性试验装置,模拟了环空不同圈闭介质形成的压力随温度的变化规律,提出了一种套管内采用硅酸铝复合隔热涂料控制环空圈闭压力的新方法,并通过窜流试验研究了不同流体圈闭压力对水泥环密封完整性的影响规律。研究结果表明:不同圈闭流体对温度的敏感性差异较大,盐水钻井液最为敏感,油基钻井液温度敏感性最小;环空圈闭压力对水泥环密封完整性影响较大,环空圈闭压力越大,水泥环气窜压力越小;套管内采用硅酸铝复合隔热涂料,可有效减少井筒约50%热量传递,增强了井筒防气窜能力,可以有效抑制环空圈闭压力,保障井筒安全。研究结果可为深水高温高压井环空圈闭压力的控制提供技术支持。

Effect of Trapped Annular Pressure on Failure of Cement Sheath Sealing

In order to solve the potential failure of cement sheath sealing caused by trapped annular pressure variations in deep-water high temperature and high pressure(HTHP)wells,the law of variation of trapped annular pressure generated by different media with temperature was simulated with a full-scale cement sheath seal integrity testing apparatus.A set of new methods to control trapped annular pressure by applying composite aluminum silicate thermal insulation coating inside the casing was proposed.In addition,the effect of trapped annular pressure generated by different fluids on the sealing integrity of cement sheath was studied through fluid channeling test.The results showed that the temperature sensitivity of different fluids trapped varies significantly,while the salt water drilling fluid is the most sensitive and the oil-based drilling fluid is the least sensitive;trapped annular pressure has a great influence on the sealing integrity of cement sheath that the higher the trapped annular pressure,the smaller the channeling pressure of cement sheath;the application of composite aluminum silicate heat-insulation coating inside the casing can effectively reduce the heat transfer of wellbore by about 50%,enhance the anti-channeling ability of the wellbore,effectively inhibit trapped annular pressure and guarantee the wellbore safety.The study results can provide technical support for controlling trapped annular pressure in deep-water high temperature and high pressure wells.