国外充气钻井液钻井技术

AERATED MUD DRILLING TECHNOLOGY

充气钻井液是一种密度范围在0．47～0．83g／cm^3之间的气（通常为空气或氮气）液（通常为水或油）混合物，钻井中将气体通过地面设备连续不断地注入钻井液，使其呈均匀气泡状分散于钻井液中，从而达到降低环空液柱压力的目的。一般在典型的以φ89钻杆钻φ152井眼时液体的泵注速度范围在0．3785～0．757m^3／min之间，气体的注入速度范围在7．08～35．4m^3／min之间，环空返出的充气钻井液，经地面除屑、除气后可重复使用。在应用过程中，由于井内流动为两相流（液-气）或三相流（液-气-固），因此钻井前需进行优化设计，达到液／气流量的最佳组合及体积优化，充分了解如何保持钻进时的压力稳定，了解在水平井和斜井中的钻井水力学等。文中对充气钻井液的气／液流量优化、水力学研究以及国外利用该技术在水平井和海上钻井的席用情阿作了详细介绍．

Aerated mud is a kind of gas/fluid mixture which density is between 0.47~0.83g/cm3. The gas which is continuously injected into drilling fluid during drilling operations is scattered into the drilling fluid in homogeneous air bubble so as to reduce annulus fluid column pressure. In general, to drill a 152mm hole with 89mm drill pipe, the liquid injecting rate range is 0.3785~0.757 m3/min and the gas is 7.08~ 35.4 m3/min. The returned drilling fluid can be reused after cuttings removing and degassing treatments. In application, as the fluid mixture in hole is two phase such as liquid/gas or liquid/gas/solid, so such works as optimum combination design of liquid and air flow rates, understanding pressure stabilization in drilling and hydraulics should be done before drilling in order to perform operations successfully. This paper details the important issues in aerated mud drilling operations such as the maintaining an optimum combination of liquid and air flow rates, hydraulics and its applications in horizontal well as well as in offshore.