可变喷距磨料射流多级切割头研制与试验

应用磨料射流切割技术切除海上采油多层废弃井口时,面临的一个突出问题是切割外层套管和隔水管时喷距变大引起作业时间增加,导致作业成本高昂。基于缩短喷距的思路,设计了一种可变喷距磨料射流多级切割头,切割头上布置有固定喷嘴和长、短伸缩杆喷嘴,每种喷嘴具有相互独立的供液流道,因此切割头可提供3种工作模式,即固定喷嘴切割模式、短伸缩杆切割模式和长伸缩杆切割模式。施工作业时,采用投球的方式依次进行3种工作模式的转换。理论计算表明,使用φ3 mm喷嘴时,长、短伸缩杆工作模式可分别将无因次喷距减小至使用固定喷嘴时的1/27与1/16.7,有效提高了射流的能量利用率。地面试验表明,可变喷距多级切割头使用方便,流道转换可靠,比普通固定喷嘴式切割头切割效率显著提高,可大幅度缩短作业时间,降低作业成本。 

Variable Jet Distance and Multi-Stage Cutting Head with Abrasive Water Jet

The crucial problem in AWJ(abrasive water jet) technique for cutting subsea oil production multi-layer abandoned wellheads is that cutting of external casing and marine riser leads to increase of operation time and excessively high cost.The paper designed a variable jet distance and multi-stage AWJ cutting head with fixed nozzles,long and short expansion link nozzles,which were different in distance and had independent fluid channels,based on the thinking to reduce jet distance.Therefore,cutting head had three operating modes,which were the fixed nozzles for cutting mode,short expansion link for cutting mode and long expansion link for cutting modes.The three working modes were switched by delivering two balls in order in the process of operation.After theoretical calculation,with 3 mm nozzle,long expansion link mode and short long expansion link mode could reduce the dimensionless jet distance to 1/16.7 and 1/27 compared with that of using fixed nozzles.It was useful to improve the utilization of jet energy.At the same time,the field trials demonstrated that this kind of cutting head with reliable method to change fluid channel was convenient to operate.Comparing with the usual fixed nozzles for cutting head,it had higher cutting rate and could reduce operation time dramatically and save cost effectively.