深水环空圈闭压力的破裂盘泄压控制模型

Pressure Relief Control Model of Rupture Disk for Annular Pressure Build-up in Deep-water Wells

井筒高温流体在生产过程中,向密闭环空传热引起的环空圈闭压力上升现象是深水油气开采面临的主要问题之一。为了保障井筒安全,结合深水油气井的生产实际,基于拟稳态传热以及耦合压力-体积的环空压力计算方法,建立了多环空圈闭压力预测模型。根据破裂盘工作原理,建立了由内向外和由外向内的破裂盘打开阀值确定方法。以西非某井为例,对生产过程中井筒温度和环空压力进行预测。套管强度校核结果表明,正常生产过程中,表层套管和技术套管存在胀破风险;在生产套管的环空泄压或者掏空后,生产套管存在挤毁风险。采用破裂盘技术后,各层套管均满足校核的要求。因此,破裂盘技术可有效实现套管的保护,对深水油气资源安全开采具有重要意义。

Annular Pressure Build-up(APB)is caused by the thermal expansion for the sealed annulus,Heated by the high temperature fluid extracted from the bottom of the well.In order to ensure the safety of the wellbore,considering the development practice in the deep-water,the multi-annulus APB prediction model is proposed based on the semi-steady heat transfer method and coupled pressure and volume annular pressure calculation method.According to the working principle of the rupture disk,the threshold valve determination methods from inside to the outside and from the outside to the inside are established.Taking a Western African well as an example,the wellbore temperature and annulus pressure during production were predicted.Casing strength verification results show that the surface casing and technical casing have the risk of bursting during normal production.When the annular pressure relieved or the production casing annulus evacuated,the production casing is at risk of collapse.After adopting the rupture disk technology,all the casings meet the requirements of verification.Therefore,the rupture disk can effectively protect casing and is significant to safe exploitation of deep-water oil gas resources.