砾石充填条件下筛管堵塞与冲蚀特性试验

An experimental study on plugging and erosion failures of sand screen in grave-packing conditions

为分析油田水源井筛管失效原因和防砂周期短的内在机制,建立一套模拟井下冲蚀和堵塞问题的砾石充填筛管防砂装置,研究筛管类型、砾石种类与粒径、生产压差等因素对筛管堵塞情况以及堵塞后筛管挡砂介质与本体的损坏情况的影响,分析筛管失效的原因和井下挡砂介质堵塞的内在机制。结果表明:在套管内砾石充填完井条件下,地层砂对砾石充填层和筛管的堵塞具有非均匀性,不同射孔孔眼部位的砾石充填层内的渗流压力分布不均,筛管过滤介质堵塞存在一定随机性;携砂流体流动时的磨蚀作用是造成筛管过滤介质失效主要原因之一;射孔孔眼流出的流体可与充填层的砾石掺混,形成磨料射流冲击正对射孔孔眼处的防砂管,造成防砂管本体的冲蚀失效;地面模拟试验结果与井下取出失效防砂管特征基本一致;试验结果能够为防砂方式的选择、生产制度的建议、筛管材质的选择、筛管结构的改进等提供依据。

An experimental set-up was developed for simulating the failure of sand control devices via gravel-packing techniques in water resource wells for oilfield application.The influence of screen types,sand and gravel sizes and production pressure on plugging and erosion of the sand screen and the damage of the production tube were investigated.The results show that,under the same downhole conditions,there is a big difference of the anti-erosion capability of the sand screens due to their structure and materials.The pressure distribution is uneven at the outlet of the perforation for the gravel pack in the annulus between the sand control pipe and the casing wall.The blockage of the sand control device is random process,which can be one of main reasons resulting in the failure of the sand screens since fluid carrying sand particles flow through the filter gaps with abrasion materials.In addition,high velocity fluid with sands and gravels from the perforation can form an abrasive jet impinging on the surface of the production tube resulting in erosion failure of the tube body.The experimental results have similar features with the erosion screens taken out from the wellbores.The study will provide guidelines for the selection of the screen materials,design of the screen structures.