Abstract:

Freezing temporary plugging technology can effectively block the oil and gas channels in the well, providing a reliable physical barrier for well control operations such astubing and casing cutting and connection, wellhead equipment repair and replacement. It has been widely used in major onshore oilfields in and abroad. However, the operating space of offshore platform is limited,andthe wellhead structure is complex,this paper mainlydiscusses the freezing temporary plugging technology of offshore platform. Combined with the wellhead string structure of an offshore platform, the temperature field changes of different structure string during freezing are simulated by using numerical simulation software, the influencing factors of freezing bridge plug bonding strength are analyzed, and the freezing effects of freezing temporary plugging technology on different structure string are compared. The results show that the freezing temperature of the temporary plugging agent under the same freezing conditions is lower and the freezing speed is increased by nearly 73%for directly frozen of 13-3/8”(339.7mm) casingcompared withthat of frozen of 20 " (508mm)riser pipe. Through in-depth research on technical improvement and optimization, this technology can play an important role in offshore well control and workover operation, and has a large development space.

Key words:

liquid nitrogen, freezing temporary blocking, well control, numerical simulation, bridge plug bonding strength

摘要：

冷冻暂堵技术可有效封堵井内油气通道, 为油套管切割与回接、井口装置修复更换等井控处置作业提供可靠物理屏障，已经在国内外陆地油田取得广泛应用。但海上平台作业空间有限!井口结构复杂，文章探讨了海上平台冷冻暂堵工艺，并结合海上某平台井口管柱结构，利用数值仿真软件模拟不同结构管柱冷冻过程中的温度场变化情况，分析冷冻桥塞黏结强度的影响因素，对比冷冻暂堵技术对不同结构管柱的冷冻效果。结果表明，直接冷冻Ø339.7 mm套管与冷冻Ø508.0 mm隔水导管相比!相同冷冻条件下暂堵剂的冷冻温度更低, 冷冻速度提升近73%。通过技术改进和优化等深入研究，该技术可在海上井控处置和修井作业发挥重要的作用，具有较大的发展空间。

关键词: 液氮, 冷冻暂堵, 井控处置, 数值仿真, 桥塞黏结强度