南海某深水高温高压气井SS-15型井口头系统薄弱点安全评价

Safety evaluation on weak points of SS-15 wellhead system in a deep water high temperature and high pressure gas well in South China Sea

为应对深水高温高压气井生产过程中井口系统复杂性、井口抬升等对整个井口系统完整性的破坏情况,研究环空压力、上顶力、温度、产量对井口头系统薄弱点的影响。基于数值模拟方法建立井口系统有限元力学模型,分析在不同环空压力与上顶力条件下,井口系统各部件的应力大小变化情况,为井口系统薄弱点位置的确定提供理论依据,进而提出深水高温高压井井口系统完整性的管控图版及方法。研究结果表明:环空密封本体与套管挂、锁环与限位槽的接触部位是薄弱点;同一环空压力下,上顶力越大,套管挂等效应力与锁环变形量越大;当上顶力超过700 t时,不论环空压力是否存在,均达到井口系统薄弱点屈服强度。因此,深水高温高压油气井应制定合理生产制度或管理措施,研究结果对保障井口系统完整性,降低深水高温高压井生产阶段风险具有一定参考意义。

In order to deal with the complexity of wellhead system and the damage of wellhead uplift to the integrity of whole wellhead system during the production of high temperature and high pressure gas wells in deep water,the influence of annular pressure,upper jacking force,temperature and yield on the weak point of wellhead system was studied.A finite element mechanical model of the wellhead system was established on the basis of numerical simulation method,and the changes in stress levels of various components of the wellhead system under different annular pressure and upward force conditions were analyzed,which provided theoretical basis for determining the weak points of the wellhead system,thus the management chart and method for the integrity of wellhead system in the deep water high temperature and high pressure gas wells were put forward.The results showed that the contact parts between the annular sealing body and casing hanger,and the contact parts between the lock ring and limit groove were the weak points.Under the same annular pressure,the larger the upper jacking force,the greater the equivalent stress of casing hanger and the deformation of lock ring.When the upper jacking force exceeded 700 t,the yield strength of the weak point of wellhead system was reached regardless of whether the annular pressure existed.Therefore,it is of great significance to establish reasonable production system or management measures for ensuring the integrity of wellhead system and reducing the risk in the production stage of deep water high temperature and high pressure wells.