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.