浮箍井下工作环境与失效分析

在整个固井过程中，固井工具及附件的工作情况是影响固井质量的重要因素，有的固井工具甚至是固井成败的关键。固井工具在井下是否正常工作，不仅要受地面操作的影响，而且井下环境也会对固井工具的工作情况产生重要影响。井下环境包括井眼、地层、套管、钻井液性能、井下温度、井下压力、循环排量及时间等综合因素，这些因素都会对固井工具的正常工作产生影响，甚至使工具失效。浮箍是一个单向阀，其功能是在注水泥后阻止水泥浆进入套管内，从而控制水泥塞高度。如果浮箍失效，就会造成水泥塞过高，外部环空不能完全封隔，有时需要补救挤水泥，固井质量低。对影响浮箍的温度、钻井液和水泥浆、循环、压差等井下环境作了详细的分析，提出了保证浮箍使用效果的一些建议。

DOWNHOLE WORKING ENVIRONMENT AND FAILURE ANALYSIS FOR FLOAT COLLAR

During the cementing process, the working condition of cementing tools and the accessories is often an important factor affecting the cementing quality. Some cementing tools are even crucial for success of the cementing job. The normal downhole working of cementing tool not only depends on the surface operation but also relies on the downhole environment, including well status, formation, casing, drilling fluid performance, downhole temperature, downhole pressure, circulation rate and time, etc. Float collar is a one-way valve, which is used to prevent the cement slurry from coming up into the casing after the grouting completed so as to control the height of the cement plug. If the float collar fails, the cement plug formed will be too high, while the external annulus cannot be completely isolated, which often requires remedial cement squeezing and the cementing quality is rather poor. In this article detailed analysis is made on the factors affecting the working of the float collar, including temperature, drilling fluid, cement slurry, circulation, pressure differential, and other downhole environment factors; and a series of advice is introduced to ensure the efficiency of the float collar.