Abstract:

A high gas-bearing well in Mahu  Oilfield suffers from hydrate freezing blockage，which results in considerable fluctuation in gas and liquid production. The surface gathering and transportation capacity is also limited. A double throttling technology is proposed to address this problem. Throttling nozzles are installed downhole and at the wellhead to control hydrates and regulate production. PIPESIM software was used to calculate the temperatures and pressure distribution in tubing and nozzles under double throttling condition. Thus，the principles of hydrate freezing prevention，wellhead production regulation，and discharge for blockage prevention were studied. Double throttling was carried out 51 times in 20 wells and its field application effects was analyzed. 5 test wells were designed to adopt the double throttling technology and thus the average cleaning interval of hydrate in production wells with serious freezing blockage problems was more than doubled. The field application results show that downhole throttle ratio is the core parameter of the double throttling process design. Reducing downhole throttling ratio improves the capacity of hydrate freezing and blockage prevention. Increasing downhole throttling ratio improves the production regulation ability of wellhead nozzle. For high gas production wells，a low downhole throttling ratio design can achieve good hydrate freezing blockage prevention results. For high liquid production wells，a high throttling ratio allows both effective wellhead production regulation and hydrate freezing prevention. This provides a solid theoretical basis for more efficient development of Mahu Oilfield.

Key words:

double throttling technology, hydrate, wellhead production regulation, downhole throttling ratio, gas liquid ratio

摘要：

玛湖油田高含气井存在水合物冻堵问题的同时产气和产液量波动较大，而现场地面集输能力有限。为解决这一难题，提出双节流工艺，即在井下与井口安装节流喷嘴进行水合物防治与调产。基于PIPESIM软件计算双节流条件下油管与双节流喷嘴温压分布，研究了双节流工艺水合物冻堵预防、井口调产以及放喷防堵原理；分析了现场20口井51井次双节流工艺现场实践效果。5口试验井采用双节流工艺进行设计，冻堵问题严重的生产井水合物平均清理间隔均提高一倍以上。现场实践结果表明，井下节流比是双节流工艺设计的核心参数。减小井下节流比可以提高水合物冻堵预防能力；增大井下节流比可以提高井口喷嘴调产能力。高产气井以水合物冻堵预防为主，应采用较低的井下节流比设计；高产液井应采用高井下节流比设计，可以兼顾井口产量调整与水合物冻堵预防效果。这一结论为玛湖油田高效开发提供了坚实的理论基础。

关键词:

双节流工艺, 水合物, 井口调产, 井下节流比, 气液比