气体钻大斜度水平井最小注气量计算方法研究

针对气体钻井如何确定合理的钻井流体力学参数的难点。以前沿用的气体钻井参数计算方法，因其依据的假设条件带有局限性，其设计气量都比实际情况偏小。为此，通过钻铤与钻杆交界面、套管与裸眼交界面进行分析和判断，以空气钻井流体力学参数设计为依据。从力学分析入手，根据空气动力学翼型的气动特性，引入薄翼理论，对岩屑颗粒进行受力分析，探讨了气体钻大斜度水平井有效携带岩屑的最小排量问题。在此基础上，提出了计算气体钻大斜度水平井流体力学参数的方法和公式，并且利用数值模拟软件对井内环空压力分布规律、环空携屑能量分布规律进行了分析，确定了水平井携岩的最小气量。计算结果与油气田实际应用情况符合性较好。

CALCULATING THE MINIMUM GAS VOLUME USED IN HIGH-ANGLE HORIZONTAL WELLS DURING GAS DRILLING

It is difficult to determine proper fluid dynamics parameters during gas drilling.Due to the limitation of the assumptive conditions of the models,the designed gas volume with previous models is always smaller than the actual.So in this paper on basis of fluid dynamics design for air drilling,the drill-collar/drill-pipe interface and casing/open-hole interface are analyzed.Starting with the dynamic analysis and the aerodynamic characteristics of the wing structure,the thin wing theory is introduced to analyze the stresses exerted on the cuttings,and then the minimum gas rate for effective cuttings removal during high-angle horizontal well gas drilling is discussed.Moreover,the method and formulae used to calculate the fluid dynamics parameters are put forward,the annulus pressure distribution and annulus cuttings-removal energy distribution are analyzed using numerical simulation software,and the minimum gas rate will then be derived.The actual field application has proven the calculation results.