Reasons and Countermeasures of Electric Submersible Pump Inverted

Electric submersible centrifugal pump (hereinafter referred to as ESP) is a high efficiency, suitable for high yield, deep well mechanical oil recovery equipment. According to information, the average liquid submersible pump liquid production is more than 2 times the pump. However, in actual production, ESP accidents often occur. According to an oil field survey statistics, electric submersible pump down rate of up to 10% to 15%. The occurrence of electric submersible pump downhole accident affected the high efficiency of electric submersible pump and reduced the output of crude oil. On the other hand, the electric submersible pump was difficult to salvage after falling into the well, causing a lot of troubles to users and causing great economic loss . According to the investigation and analysis of the accident of falling into the ground, it is found that there are two direct causes for the electric submersible pump to fall into the well. One of them is that there are two direct reasons for the fall of the electric submersible pump: one is that the connection thread between the pump section of the electric submersible pump, the pump cylinder and the pump head or between the electric submersible pump system and the oil pipe Hereinafter referred to as the pipe thread connection) Department, due to the failure of the inverted block caused by the inverted buckle down. The second is submersible pump pump section or motor section between the joint bolts caused by the rupture of the fall. Now the main analysis of undercutting issue. Analysis of the causes of ESP submersible buckling According to the survey on the accidents of back-up and dropouts on the spot, there are three reasons for the ESP submersion: First, there is a large reverse torque when the ESP is started and normal operation . This is because the electric submersible pump pipe joints are threaded connection right (M90 × 1.75), and the direction of rotation of the motor clockwise, the motor output torque through the multi-stage centrifugal pump shaft and impeller, guide wheel Passed to the pump cylinder, cylinder pump in the buckle direction of rotation. Especially in the electric submersible pump starts, the starting torque is larger and there is a greater impact, the impact of torque in this role, most likely make the pipe thread connection undercuts. Second, the submersible pump pipe thread preload is not enough (or pre-tightening torque is not enough). The size of the pre-tightening force is an important factor affecting the reliability of the threaded connection. The pre-tightening force can neither be too large nor too small. On the electric submersible pump pipe thread connection, on the one hand, taking into account the submersible pump in the work there is inverted torque, the pre-tightening force of each pipe thread connection should be able to ensure that the axial load of the electric submersible pump system (including the electric submersible pump System self-weight, fluid pressure and preload, etc.) and the horizontal undercut torque under the joint action will not happen undercut phenomenon, even if the pre-tightening torque is greater than a certain amount of undercut torque; on the other hand, the pre-stress can not be too large . If the preload is too large, coupled with the role of submersible pump axial load, it is possible that the thread cross-section of the axial tensile stress exceeds the yield point of the pump cylinder material, plastic deformation occurs at the pump cylinder thread, leading to pre Tight relaxation. At this time, although the two members do not rotate relative to each other, the threaded connection has loosened. If there is reverse buckling torque at this time, this buckling torque all bear by the anti-pouring block; if the anti-pouring block is not strong or insufficient strength, it will cause the anti-pouring block off or be cut off, resulting in electric submersible pump down Buckle well. This shows that the preload should have an appropriate value. However, the actual production of electric submersible pumps used in the design of the pipe thread connection is not pre-tightening accuracy of the calculation, the process does not have the pre-tightening force on the size of the strict control, which is leading to the importance of thread undercut the reason. Third, the anti-down process is not reliable. Due to the existence of submersible ESP electric submersible pump problems, so pipe threaded joints set anti-pouring block. Due to the small thickness of the anti-pouring block, the weld section size is small, carrying capacity is not strong; combined with anti-block and pump head, cylinder are medium carbon steel, welding process is poor, difficult to guarantee the quality of the weld. Therefore, the anti-dumping anti-dumping function is not reliable. This is precisely illustrated by the frequent occurrence of anti-to-block desoldering or even shearing in production. Electric submersible pump system 2 ways to prevent undercutting 2.1 Reasonably determine the pre-tightening torque of each pipe thread connection According to the above analysis, the actual pre-tightening torque (Mrb) of each pipe thread connection, we must first ensure that the electric submersible pump axial load and work In the actual existence of undercut torque (Mrp) under the action of the thread does not loosen. For triangular threads, the torque Ms required to tighten the threads and the required torque Mp to loosen the threads should be, respectively, unless the effect of the axial load is taken into account: Ms = dFb-tan (α + φv) / 2 dFb-tan (α-φv) / 2 (2) where d is the diameter of the pipe thread, in mm; Fb is the thread preload, N; α is the lead angle of thread, 24; φv is the delta- Angle, 9 ° 36. Substituting the thread-related parameter Ms = 1.1Mp (3) means that the torque required to tighten the thread should be greater than the torque needed to loosen the thread. For electric submersible pumps, the maximum reverse torque Mrpmax actually exists in the work is the starting torque Mst. When the electric submersible pump starts with load, the starting torque is 1.1 ~ 2.4 times of rated torque MR (1.4 ~ 1.8 times for common 30 ~ 55kW motor), that is, Mrp = Mst = To prevent the electric submersible pump in the work due to frequent start-up and flip, the actual pre-tightening torque Mrb satisfy Mrb = Ms-Mrp / Mp = (1.54 ~ 1.98) MR (5) that the actual pre-tightening torque should be greater than 1.54 to 1.98 times Of the rated torque; the other hand, the thread can not be the actual pre-tightening torque, that is, the actual pre-tightening torque generated by the actual pre-stress can not be too large. The relationship between the pre-tightening force of the thread and the yield point σs of the screwed material and the minimum cross-sectional area Amin of the screw thread is as follows: Fb ≦ (0.5-0.7) σs-Amin (6) If the pre-tightening torque , In the thread cross-section of the preload force exceeds the range (6), should consider increasing the pump cylinder wall thickness or change to use a higher yield point barrel material. 2.2 to change the electric submersible pump pipe thread rotation right-handed change to left-handed, so that the electric submersible pump in the start-up and normal operation of the torque generated will not cause loosening of the screw. Of course, in the submersible pump work process, due to overload, underload and other causes of the motor power failure, but also in an instant undercut torque, but the torque compared with the starting torque is much smaller, will not cause electricity potential In addition, to strengthen the existing anti-dumping measures, strict control of anti-pouring block welding process, to ensure the quality of welding, but also can play a role in preventing undercuts. Submersible pump workflow The above measures to prevent undercut, can not fundamentally solve the problem of undercutting. Of course, it is impossible to completely eliminate the back-up torque because the torque causing the back-up is not eliminated. But take some measures to control the back-up torque within a certain range. For example, at the junction of the uppermost section of the electric submersible pump and the oil pipe, the movable joint as shown in FIG. 1 can be used to control the undercutting torque within a certain range to avoid the undercutting. The working principle of the joint is that during assembly, the adjusting screw is used to properly control the pressing force between the steel ball and the upper joint so as to ensure that the relative rotation between the upper ring and the lower ring does not occur during normal operation of the electric submersible pump. When the torque exceeds a certain value, the upper joint presses the steel ball into the hole of the upper ring, and the relative rotation between the upper ring and the lower ring causes the torque to be controlled within a certain range, thus preventing the buckle from buckling.

Reduced Shank Twist Drill Bit

Reduced Shank Twist Drill Bit,Reduced Shank Drill Bit,Reduced Twist Drill Bit,1/2 Reduced Shank Drill Bit

Jiangsu Kidea Industry Co., Ltd. , https://www.jskidea.com