Abstract: In order to measure the load,stress and strain of oil tube,a device for measuring the load was developed,and a test bench for simulating the operation situation of tube was set up.Based on the experimental data,the stress and strain of oil tube were calculated by means of the finite element software ANSYS.The results show that the tube in pumping well is subjected to tensile-tensile fatigue load and situated in the condition of forced vibration with damping,which may be the basic factors resulting in the fatigue fracture of tube.The most dangerous point is at the root of the first engaged tooth of a joint.Generally,the biggest values of stress and strain may exceed the yield limit.Though the stress and strain values are high,the elastic stress and strain amplitudes at the most dangerous points are low,so as the oil tube can go into service for a long time.When non-normal conditions appear,the biggest stress and strain would get into the strengthened phase,and the larger plastic strain amplitude will be produced under the action of a circulating load,which results in the fatigue fracture of oil tube.

Key words: pumping well, oil tube, fatigue fracture, load, stress and strain, simulation

摘要： 将自制开发的新型载荷测试仪和模拟油管工况测试台,成功地用于油管载荷及应力应变的实测试验.在此基础上,应用大型有限元分析软件ANSYS,对油管在各种工况下的应力和应变进行了计算.结果表明,抽油机井油管受到的是拉-拉疲劳载荷,处于有阻尼强迫振动状态,是油管产生疲劳断裂的基本条件.最危险点在接头的第一啮合齿的齿根处,最大应力应变值一般均超过屈服极限.在正常工况下,尽管危险点应力应变水平很高,但是仍处于低弹性应变幅循环状态下,所以油管能较长期地在井内服役;当发生非正常工况时,油管内的最大应力应变幅可能达到强化段,在循环载荷作用下会产生较大的塑性应变幅,就会发生油管的疲劳断裂.

关键词: 抽油机井, 油管, 疲劳断裂, 载荷, 应力, 应变, 模拟计算