| Summary: | Supercritical CO2 (SC-CO2) fluid has the properties of low viscosity and high diffusion capacity near to gas, and higher density near to liquid. Compared with nitrogen, air, liquid, aerated fluid, foam and other drilling fluids, the supercritical CO2 fluid has a wide range of density which can not only allow it to generate enough torque to run a downhole motor, but also ensure the downhole condition is in an underbalanced state while drilling. Even if the supercritical CO2 fluid invades into reservoir, the reservoir will not be damaged, on the contrary, it can increase the reservoir porosity and permeability further more, reduce flow resistance, and enhance production and recovery. Meanwhile, the velocity of a supercritical CO2 jet is faster than that of water jet and the threshold pressure is lower also resulting in improved rock breaking. When the coiled tubing drilling with supercritical CO2 takes place, it can significantly decrease the coiled tubing drilling system pressure and expand the coiled tubing operating range, it is more suitable for slim hole, microhole, short radius horizontal wells, and complex structures wells. The coiled tubing drilling with SC-CO2 will bring an innovation in the drilling technology, and will become an efficient drilling technique for special reservoir development. 摘要: ： 超临界CO2流体具有接近于气体的低黏度和高扩散系数，同时具有接近于液体的高密度。与氮气、空气、液体、充气液、泡沫等钻井流体相比，超临界CO2流体的密度变化范围较宽，这一特性使得超临界CO2为井下马达提供足够扭矩的同时，还能保证井底的欠平衡状态。即使超临界CO2流体侵入储集层，也不会对其造成伤害，相反还能进一步增大储集层孔隙度和渗透率，降低流动阻力，提高采收率。同时超临界CO2射流破岩速度较水射流快得多，而且破岩门限压力也非常低，在利用连续油管进行超临界CO2喷射钻井时，可大大降低连续油管钻井系统的压力，扩大连续油管的作业范围，更适合小井眼、微小井眼、超短半径水平井、复杂结构井等钻井。超临界CO2连续油管钻井将为钻井带来一次全新的技术创新，也将成为特殊油气藏开发的高效钻井技术。图10表1参15 Key words: coiled tubing, drilling, supercritical carbon dioxide, feasibility analysis
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