Compared with mechanical well killing technologies,the fluid based well killing technology is more advantageous with a simple process,high safety and controllable costs so it has gradually become a common well killing technology for the workover of gas wells.So far,however,its construction technologies have not been researched systematically.In this paper,a technical idea of well killing and workover operation without pressure release based on the fuzzy-ball fluid piston technology was proposed after the research results of well killing technologies used in domestic workover operation were analyzed and summarized.Then,a series of studies were conducted from the aspects of dosage calculation,pumping mode selection,pumping process design and flowback pattern selection of fuzzy-ball fluid in gas wells.Finally,comparative analysis was carried out based on field application.And the following research results were obtained.First,calculate the height of fuzzy-ball fluid piston and its viscosity at a low shear rate based on the internal structure force required to balance the maximum buoyancy of the bubble in the wellbore,and accordingly determine the properties of the fluid that is prepared on site.Second,calculate the volume of fuzzy-ball fluid to keep the hydrostatic column pressure in the wellbore according to the demand for formation pressure balance,with an additional pressure value of 3-5 MPa for safety.Third,pump the water pad fluid with a liquid column height of 500 m,improve the pumping efficiency by wetting siring and borehole wall,and increase the flowback efficiency through the formation of a slurry mixture section of low-viscosity and low internal structure force with the fuzzy-ball fluid.Fourth,select the pumping mode of positive/reverse circulation according to the connection state and resistance to pressure of strings.Fifth,after the workover,select direct gas lift or gel-breaking gas lift for production recovery according to the depletion degree of formation energy in a gas well.This technological process was practically applied to three gas wells in NW and SW China.Among them,two wells recover to the previous production rate after continuous gas lift for 2-3 days.It is concluded that this technology can well solve the problems in the process of conventional pressure release,such as poor safety and productivity waste,and shorten the operation cycle of gas well killing.%较之于机械手段,采用流体手段压井具有工艺简单、安全性高、成本可控等优势,已逐渐成为气井修井作业常用的压井手段,但目前对其尚缺乏系统的施工工艺技术研究.为此,在分析总结国内修井作业中压井技术研究成果的基础上,提出了绒囊流体活塞技术不降压压井修井作业的技术思路,开展了气井绒囊流体用量计算、泵入方式选择、泵入流程设计以及返排方式选择等方面的研究,并结合现场应用实例进行了对比分析.结果表明:①根据平衡井筒气泡最大浮力所需内部结构力,计算出绒囊流体活塞的高度和低剪切速率下的黏度,据此确定现场配制流体的性能;②根据平衡地层压力要求计算井筒内静液柱压力所需绒囊流体体积,并附加3～5 MPa的安全压力值;③作业时,泵入液柱高度为500 m的清水前置液,润湿管柱、井壁以提高泵入效率,并与绒囊流体形成低黏度、低内部结构力混浆段提高返排效率;④根据气井管柱连通状态及管柱承压能力选择正反循环泵入方式;⑤修井结束后,根据气井地层能量衰竭程度选择直接气举或破胶气举返排实现复产.现场应用于我国西北、西南地区的3口气井,其中2口井连续气举作业2～3 d,气井产量便恢复至作业前等产量点.结论认为,该项工艺较好地解决了常规降压过程导致安全性差、产能浪费等问题,缩短了气井压井作业周期.
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