泡沫钻井水力参数优化方法研究

泡沫钻井在国内外已得到广泛应用,但关于水力参数优化设计的方法还未完善。基于多相流理论和携岩理论,通过理论计算和分析,总结出泡沫钻井水力参数优化设计方法,即通过临界气液比与井口回压线性关系确定最优气液比;通过不同井深下最低井底压力确定最优井口回压,结合最优气液比、最优井口回压、井底压力、岩屑浓度确定最优泡沫流速,最后根据最优泡沫流速确定最优注气流量和注液流量。实例计算了井眼直径为200 mm、钻杆外径为114.3 mm、井深为1 980 m、钻速为9m/h、18 m/h、27 m/h对应的最优水力参数。提出的优化方法对泡沫钻井水力参数优化有实际指导意义。

Study on method for optimizing hydraulic parameters in foam drilling

Foam drilling has been widely used both at home and abroad, but the method for optimized design of hydraulic parameters has not been improved. This paper concluded the method for optimized design of hydraulic parameters for foam drilling based on multi-phase flow theory and sand carrying theory, and through theoretical calculation and analysis. That is, to determine the optimum gas/liquid ratio through the linear relation between critical gas/liquid ratio and wellhead backpressure; to determine the optimum wellhead backpressure through minimum bottom hole pressure in different depths; to determine the optimum foam flow rate by combining the optimum gas/liquid ratio, optimum wellhead backpressure, bottom pressure and cuttings concentration; and finally to determine the optimum gas injection flow rate and liquid injection flow rate according to optimum foam flow rate. Example calculations were conducted for optimum hydraulic parameters corresponding to 200 mm hole diameter, 114.3 mm out diameter of drill pipe, 1 980 m well depth and 9 m/h, 18 m/h and 27 m/h drilling rate. The optimized method presented in this paper has a practical guiding significance for optimizing hydraulic parameters of foam drilling.