塔里木油田哈拉哈塘、哈得等区块裸眼完成的油气井,因井壁垮塌、出砂,严重影响正常生产。常规液力冲捞砂工艺在这类低压、易漏井中无法建立循环，难以完成冲砂需求。通过分析研究提出一种用双壁钻杆加井口注氮气的冲砂工艺,并用瞬态多相流软件OLGA进行模拟。分析了钻杆内外两种不同注入方式下,井筒内注入气及冲砂液复杂的流动现象。得出钻杆外注氮气无冲砂效果、钻杆内注气能搅动冲砂液在井筒内形成闭式循环的结论。最后通过参数的敏感性分析,针对钻杆内注气的双壁冲砂工艺,得出结论:最佳注气量为13 308 ～26 617 m3/d;注气阀的合理位置为静液面处;管柱的理想组合为内管长度 1 000 m、外管尺寸127 mm;冲砂过程始终为负压。该工艺在塔里木油田的成功应用,为深层低压井的冲砂提供了技术借鉴。

Such areas as Halahatang, Hade in Tarim oilfield are afflicted by significant production loss attributed to serious sandingfrom openhole completion, wellbore collapse.Sanding manifests itself in such forms as borehole collapse in open hole and sand burial.Conventional underbalanced sand flushing techniques often fail to prevail such technical challenges as low pressure, leakage and circulation loss in carbonate reservoirs in Tarim oilfield.In this paper, a process of nitrogen injection to flush sand with dual-wall drill pipe is presented.With dynamic multiphase software OLGA, a computer model thereof is built to simulate such a complex process.Gas injection both inside and outside of drill pipe are simulated respectively to analyze complicated flow phenomenon related to injection gas and sanding fluid within the wellbore.It is concluded that gas injection outside of drill pipe is futile, whereas gas injection inside it can agitate sanding fluid to form a closed loop within the wellbore.As for the latter injection scheme, the following four results are found by parametric analysis: 1) the optimum gas injection rate is between 13308 and 26617 m3/d; 2) sensible position for gas injection valve is near to static liquid level;3) pipe assembly is optimized to have inner tube length of 1000m and outer pipe size of 127mm; 4)the entire sanding process shall always be under negative pressure.Being applied successfully in Tarim oilfield, this technique has provided an insightful reference to sand flushing in deep zone wells with low pressure.