Research On Improving Cementing Quality Of Deep Gas Wells

In deep gas well cementing,there are several difficulties such as annulus pressure at wellhead,poor cementing quality of two interface,gas channeling among layers,CO2 corrosion and so on.These problems affect the production of gas well,decrease gas recovery and go against the subsequent operations.When the ones are not prominent,it would increase the cost of production operations.However,when they become severe,the well group will even be scrapped.In order to solve these problems,this article is on the base of the cement ring seal failure mechanism research,and concluded that the cement ring seal failure is mainly embodied in the destruction of interface and itself performance of the cement ring.Also designing and optimizing the slurry materials is the only method to improve it.Specific measures include optimization of ement slurry performance parameters,to prevent volume shrinkage of cement stone,enhancing the ability of preventing cement corrosion and improving the mechanical character of cement stone.In addition,latex and fiber can effectively improve the brittleness of cement stone and reduce the modulus of elasticity based on the cement microstructure analysis.Based on the mentioned analyses,latex cement slurry system,the expansion and fiber cement slurry system and corrosion prevention cement slurry system were developed.These three kinds of slurry system have the wide temperature range,good stability of the slurry,low fluid loss,fast strength development and adjustable thickening time.Besides,latex cement slurry system has a unique film-forming property so that it can increase the resistance of the flow of oil,gas,and water,enhance the cementation ability of the interface and make cement stone elastic.The expansion and fiber cement slurry system can improve the filled level of the annulus,promote the development of compressive strength of cement stone,has the superior mechanical properties and better cementing quality between the second interfaces,and supply the better cement stone for the subsequent operations.Corrosion prevention cement slurry system has a good ability of anticorrosion CO2.According to the specific condition of different regions,the three kinds of slurry system have been successfully applied to horizontal well Longshen 2-Ping 1,two deep wells in Niudong area of North China,and many wells with high CO2 in Songliao Basin,and have been very effective.