增加套管内外压差提高固井质量

如何提高固井质量是钻井工程长期以来所面对的问题。应用中厚壁管力学理论，从力学的角度分析了在固井过程中套管应力和应变之间的关系，提出了增加套管内外压差来提高固井质量的技术思路，通过施加外挤压力使套管具备弹性能，在水泥浆候凝发生径向体积收缩时，通过释放弹性能，弥补体积收缩产生的微环隙，消除了气窜通道，从而提高固井质量。通过10多井次的气井固井实践，结果表明：该技术能有效地消除或减少固井后期因套管应力应变发生变化而出现的微间隙，对提高固井质量，取得了良好的效果。建议在井下条件允许的情况下，增加环空与套管内的压差值来提高固井质量。

Improving cementing quality by increasing pressure differential between the internal and external casing

How to improve the cementing quality is an issue the drilling engineers are always facing. This paper analyzed the relationship between the stress and strain on the casing during cementing operation based on the theory of medium thick wall pipe mechanics, and then suggested increasing the pressure differential inside and outside the casing to improve the cementing quality. Once the external compression is exerted on the casing, there will produce inside the casing a kind of elastic energy, which will be released when the cement stone shrinks during the WOC to make up the micro annulus produced by cement shrinkage to avoid gas channeling. The cementing quality is thus improved. The applications in over 10 wells have proved that this method could effectively eliminate or reduce the micro annulus created by the casing stress change and casing strain change during the later stage of the cementing job, thus to improve the cementing quality. So it is recommended that the pressure differential between the casing and the annulus be increased to improve the cementing quality if the downhole conditions permit.