气井套管环空密封失效预防措施初探

Preliminary preventive measure for casing annular seal failure in gas well

针对当前气井环空带压问题日益严重、治理难且治理成本高的现状,提出了一种气井环空密封失效预防措施。理论验证了该措施的有效性,对措施中关键材料性能的影响规律进行了分析,以确定材料种类,并试制了室内试验试样。研究表明:通过在套管外壁黏附一层特定厚度和力学性质的缓冲层,改善套管压力下水泥环的受力状况,这种预防因水泥环破坏而造成环空密封失效的措施,在理论上是可行的;通过对缓冲层材料性能的影响规律分析,优选出套管缓冲层弹性模量应小于10.0 MPa、泊松比在0.20～0.50、厚度大于4.0 mm,并初步确定缓冲层材料为橡胶。试样试制过程表明,该措施经济、简便,可操作性强,为气井环空带压的预防提供了一种新的思路。

Considering the serious problems of sustained casing pressure and high-cost treatment,a new method for failure prevention of annular seal was developed.The validity of the method was verified by theoretical calculation.In order to determine the key material,the influence of properties of the material was studied,and finally the experimental prototype was developed.The study shows that the method of adding a buffer layer with particular thickness and mechanical properties on the outer wall of casing and improving the stress condition of cement sheath to prevent the failure of the seal integrity of annulus is feasible in theory;the elastic modulus of buffer layer should be less than 10.0 MPa,Poisson′s ratio 0.20￣0.50 and the thickness larger than 4.0 mm,the buffer material is initially identified as rubber.The new measure is economical,simple and easy to operate,providing a new way for the prevention of sustained annulus pressure in gas wells.