局部欠平衡钻井回流装置结构设计及流场模拟

Structure Design and Flow Field Simulation of Partial Underbalanced Drilling Reflow Device

为了提高机械钻速并解决常规欠平衡钻井的常见问题而提出了连续管调制局部欠平衡钻井技术。回流装置是该技术中上端连接钻铤(钻杆),下端连接钻头并且沟通内、外环空的重要装置。在正常钻进过程中,钻井液经连续管和钻头水眼后上返至环空,并经过回流装置进入钻杆与连续管形成的微环空。设计了适用于连续管调制局部欠平衡钻井技术的回流装置,对回流装置进行了结构设计和强度校核,并用数值模拟的方法对回流装置外侧的流场进行研究。研究结果表明:井底上返岩屑流一部分从回流装置相邻开孔之间逸出,一部分直接经过开孔流入微环空;逸出部分中的部分岩屑下返经开孔流入微环空;随着开孔内外两侧压差增加,岩屑的速度增大。所得结论可为局部欠平衡钻井回流装置的优化设计和现场应用提供参考。

In order to improve the ROP and to address the common problems of conventional underbalanced drilling, a coiled tubing modulated partial underbalanced drilling technology is proposed. The reflow device is an important device in this technology. During the normal drilling process, the drilling fluid flows down through the coiled tubing and the drill bit, and then returns to the annulus, passing through the reflow device to enter the micro annulus formed by the drill pipe and the coiled tubing. The reflow device suitable for coiled tubing modulated par-tial underbalanced drilling technology was designed. The structure design and strength check of the reflow device have been conducted. The flow field outside the reflow device has been studied by numerical simulation. The nu-merical simulation results show that a part of the cuttings flow from the bottomhole escapes from the adjacent open-ings of the reflow device, and the rest flows directly into the micro annulus through the openings. Part of the es- caped cuttings flow down into the micro annulus through the openings. With the pressure difference in the hole in-creases, the cuttings velocity increases.