水力喷射多级压裂井下工具磨损规律分析

Wear investigation of downhole tools applied to hydra-jet multistage fracturing

水力喷射压裂是一种集射孔、压裂及水力封隔一体化的增产改造新方法,井下工具(喷枪)作为保证该技术成功实施的关键因素之一,其工作寿命直接关系到该技术的施工效果。把现场应用后部分存在磨损的喷枪剖开后,分析了喷枪内部喷嘴周围及外表面磨损较严重的区域,再利用数值方法模拟计算了喷射压裂时工具内部流场,研究了井下工具内部流道附近易磨损区域形成原因。结果表明:返溅回来的磨料射流会对喷枪外表面形成返溅冲蚀,下层喷嘴外表面受到返溅冲蚀伤害比上层喷嘴严重;在胶结较差的地层,高速磨料射流可能进入地层并通过已有的射孔孔眼冲蚀喷枪或油管外表面;同一喷枪的内部,上层喷嘴上缘和下层喷嘴下缘属于易磨损区域,喷枪内部流场的数值模拟结果很好地解释了出现该现象的原因。因此,研究该技术中使用的井下工具磨损规律对于改进工具结构、提高喷枪寿命和水力喷射压裂成功率具有实际参考价值。

Dow nhole tools are one of the critical factors to guarantee the successful application of hydra-jet fracturing technology which is a new stimulation method with perforating ,fracturing and hydraulic sealing . Some donwhole tools are cut open and the severe wear areas around the nozzle inlets inside them and on their surfaces are analyzed .In order to investigate the reason for the inside wear ,the flow field inside the tools are numerically simulated .The results show that the splashback abrasive jet will erode the surface around the nozzles of the tool .For surface wear at different positions along the tool axis ,it will be more serious at the downstream than that at the upstream .At the same time ,if the formation is loose ,the abrasive jet with a high velocity will splash into formation and return from other existed perforations , resulting in extra wear at the surface relatively far from the nozzles or even the tubing ’s surface .For the inside of the tools ,the wear at the upper area around the upstream nozzle inlet and lower area around the downstream nozzle inlet will be more obvious than that of other positions .The numerical simulation results explain this phenomenon clearly .T he research provides reference for improving the dow nhole tool ’ s structure and its life .