There are several reasons for the sudden leakage of the screw pump during normal operation. One is the leakage of the mechanical seal, the other is the misalignment of the installation, the shaft sleeve is worn, the pump body and the bushing of the pump are integrated (collectively referred to as the pump body), and the shaft seal is a mechanical seal. Screw pump has a variety of structural forms, generally a small flow of 0.2~6.5 m3/h, the pump body and bushing into one (collectively referred to as the pump body), the shaft seal is a mechanical seal. The infusion body in the pump for axial uniform linear motion, so the pressure pulsation is small, stable flow, low noise, due to the rotating parts of small inertia, the starting torque and vibration is very small. The main causes of sudden leakage during normal operation of screw pump are: evacuation, cavitation or pressure suppression for a long time, resulting in seal damage; The actual output of the pump is too small, a large amount of medium pump circulates, heat accumulates, causing medium gasification and sealing failure. The large return flow rate causes sediment at the bottom of the container (tower, kettle, tank and pool) on the side of the suction pipe to float and damage the seal. For long-time shutdown, there is no manual turning gear when restarting, and the sealing surface is damaged due to adhesion of friction pair.
When the screw pump is working, because the two driven screws are symmetrically meshed with the active screw, the radial forces acting on the active screw are all balanced, and the active screw does not bear bending loads. The radial force of the driven screw is supported by the cylinder bushing along its entire length, so that no additional bearing is required at the outer end and basically no bending load is carried. During operation, a layer of oil film formed between the outer surface of the screw and the inner wall of the pump cylinder can prevent direct contact between metals and greatly reduce the wear of the screw tooth surface.
Screw pump in use to know what place?
1. Downhole gas separation: invalid pump operation is often caused by gas interference, which can be diagnosed by sonic liquid level measurement and indicator diagram. It is preferable to place the pump suction port below the fluid entry interval, and if placed above, use a gas separator. If the valve seat sub is arranged at least 10ft below the bottom of the fluid inlet interval, effective gas separation can occur in the annulus, and the sleeve acts as the outer cylinder of the separator. However, the conditions of the well often do not allow the pump to be placed below the fluid entry layer, so consider using a downhole gas separator. The regular gas separator consists of the fluid inlet part (e. g. perforating sub), the outer cylinder (e. g. a fuel-saving pipe with a plug at the bottom) and the liquid sealing pipe at the bottom of the pump.
2. Diagnosis of low energy effect: The diagnosis method is to determine the total rate of the pumping system, and to determine the total rate only needs to measure the power of the input prime mover, measure the bottom hole production pressure and accurate production test data. Generally, the total speed of the beam pumping system should be half, if it is lower than this, its performance should be improved. Techniques to increase the overall rate include maintaining a high volumetric rate (matching pump specifications to wellbore injection, eliminating gas interference, controlling pumping with an evacuation controller or timer) and replacing an oversized motor.
3, the power meter to measure the pump full coefficient percentage, the application of integrated data acquisition system can simultaneously obtain motor power and power data. One of the main uses of the indicator diagram is to diagnose how the pump is operating and to analyze downhole problems. The production level measurement combined with the indicator diagram can be used to know whether the well is producing with large production, whether the height of the liquid column is higher than the depth of the pump suction inlet, whether the pump is not fully filled and whether the free gas moves upward along the casing annulus.
4. Control the pump displacement, which can be controlled by adjusting 4 numbers: plunger size, punch degree, pump punch number and daily running time. Due to the high cost of the equipment, it is usually not suitable for the pump size. The simpler approach is to change the configuration of the ground equipment, such as moving the beam rod to change the stroke length of the ground and the pump; the second is to replace the motor pulley to control the number of pumps. The matching of pump volume and well productivity can be achieved by changing the daily operation time. The following devices can be used to control the operation time: empty pumping controller, interval timer and percentage timer. If the empty pump controller detects that the pump is not fully filled, it will stop the pump. The timer controls the running time of the pump, which is relatively cheap and simple to operate. The duration of the pump shutdown should be as short as the bottom hole production pressure does not rise by more than ten percent of the reservoir pressure. The operator can carry out the above-mentioned acoustic wave and dynamometer measurements for 45min for each well to determine the well productivity, downhole pump dynamics, downhole gas separator dynamics, sucker rod and beam pumping unit loads, and motor dynamics. Through 45min analysis, the operator can make the well production to reach a large, operating costs to reduce.
5. The sonic liquid level shall be measured to determine the relative depth between the liquid level and the pump suction inlet. If the liquid level is higher than the pump suction, the well cannot be produced at a high yield. If the gas interference affects the yield, the liquid level is higher than the pump suction inlet; if the pumping capacity is too large to cause low production, the liquid level should be at or near the pump suction inlet.