反循环气体钻井压力计算分析

摘要

In air drilling, the volumetric flow rate of air is critical to the success of under-balanced drilling. Air or other gases are highly compressible so the volumetric flow rate is closely related to pressure which is comprehensively studied by a lot of researchers. Take air as an example, equations calculating pressures in drill pipes and in annular space are derived and general solutions of the equations obtained. By defining the equation constants from boundary conditions, the change of pressure with temperature and well depth is solved, from which air volumetric flow rate can be calculated. This calculation provides the basis for drill-ing rig selection.%气体反循环钻井在中国刚刚起步,很多理论分析、计算方法尚未形成,急需开展气体反循环钻井理论方面研究,为气体钻井的设计、设备选型、工艺参数优化提供理论保证和技术支持.气体体积流量是保证欠平衡钻井施工的关键,由于采用具有极大压缩性的气体作为循环介质,循环系统的体积流量与压力变化密切相关,因此空气钻井压力计算成为研究重点.对钻柱和环空处分别进行了压力公式推导.以空气钻井为例,求出各处公式通解.根据边界条件确定常数,获得压力随温度和井深变化的规律,进一步计算即可确定体积流量,为选择钻机设备等提供依据.