井口隐患治理关键技术研究与应用

传统治理井口隐患的压井方式对储层伤害严重，机械封堵又受客观因素影响较大。冷冻暂堵技术不受管柱尺寸、背压阀结构等条件限制，可对冷冻暂堵桥塞反向试压，实现泄漏井口装置的带压更换,已逐步成为国内井口隐患治理作业的主流技术手段。然而冷冻暂堵技术在施工过程中，暂堵剂配方、冷冻时间等关键技术参数均由工程师经验决定，往往不能给出准确的参数取值，存在安全隐患。结合室内实验及现场施工，研究了影响冷冻暂堵作业能否顺利实施的关键技术，包括暂堵剂配方、暂堵剂注入量、冷冻温度及冷冻时间。结果表明，暂堵剂最佳配方为水、黏土、增黏剂的体积比为2∶1∶1；计算暂堵剂注入量需附加1.2~1.4的修正系数；?20 ℃为形成冷冻暂堵桥塞的临界温度；井口压力降至最小值后开始上升时的时间点为冷冻时间的临界点。研究成果现场应用效果良好，对于优化施工设计、降低作业成本及人员劳动强度具有重要意义。

Study and application of the key technologies for wellhead hazard treatment

The tradition well killing method for treating wellhead hazards usually brings serious damage to reservoirs and the mechanical plugging technology is affected more by objective factors. The frozen temporary plugging technology is beyond the restriction of the size of pipe string and the structure of counter balance valve, and it can be used for the back pressure test of frozen temporary plugging bridge so as to realize the replacement of leaked wellhead device under pressure. And it has been gradually become the mainstream technology for wellhead hazard treatment in China. In the operation process of frozen plugging technology, the key technical parameters (e.g. the formula of temporary plugging agent and the freezing time) are all determined by the engineers based on their experience, so they cannot be valued accurately, leading to safety hazards. In this paper, the key technologies to ensure the smooth implementation of frozen plugging operation were studied based on laboratory experiments and field operation, including formula of temporary plugging agent, injection rate of temporary plugging agent, freezing temperature and freezing time. It is indicated that the optimal formula of temporary plugging agent is water, clay and viscosifier with the volume ratio of 2∶1∶1, the calculated injection rate of temporary plugging agent shall be optimized with the correction coefficient of 1.2-1.4, ?20 ℃ is the critical temperature for the formation of frozen temporary plugging bridge, and the moment when the wellhead pressure begins to rise after dropping to the minimum value is the critical freezing time. The research results present good field application effects and are of great significance to optimize the construction design and reduce the operation cost and labor intensity.