How to keep high production rate of screw pump
Date of issue:[2020-08-17] Click through rate:Screw pump is the most commonly used mechanical oil extraction method in the world, and its most common operation problem is that the pump can not be fully filled, resulting in low productivity. The incomplete filling of pump is due to the pump capacity greater than the well output or the poor gas separation at the pump inlet, and part of the pump displacement is lost due to the interference of gas in the pump and the control of the pump operation time, so as to make the pump displacement and flow Matching the amount of fluid entering the bottom hole can improve the efficiency and reduce the cost. The specific methods to maintain the high production rate of screw pump are as follows:
1. Sound wave liquid level measurement should be carried out to determine the relative depth between the production liquid level and the pump suction inlet. If the liquid level is higher than the pump suction, it is impossible for the well to produce at maximum production. If the gas interference affects the production rate, the liquid level is higher than the pump suction; if the pumping volume is too large to cause low production, the liquid level should be at or near the pump suction.
2. The motor power and indicator data can be obtained simultaneously by using the comprehensive data acquisition system. One of the main uses of indicator diagram is to diagnose how the pump works and to analyze downhole problems. The application of production liquid level measurement combined with indicator diagram can be used to know whether the well is producing at the maximum production rate, whether the liquid column height is higher than the depth of the pump inlet, whether the pump is not fully filled and whether the free gas migrates upward along the casing annulus.
3. Diagnosis of low energy efficiency wells. The diagnosis method is to determine the total efficiency of the pumping system, which only needs to measure the input power of the prime mover, determine the bottom hole production pressure and accurate production test data. Generally, the total efficiency of beam pumping system should be about 50%. If it is lower than this, its performance should be improved. Techniques to improve total efficiency include maintaining high volumetric efficiency (matching pump size with wellbore injection volume, eliminating gas interference, controlling pumping with a pumping controller or timer) and replacing excessive motors.
4. Downhole gas separation. Invalid pump operation is often caused by air interference, which can be diagnosed by acoustic liquid level measurement and indicator diagram. It is best to place the pump suction at the bottom of the fluid into the zone, if placed above, gas separator should be used. If the valve seat nipple is arranged at least 10ft below the bottom of the fluid entry section, effective gas separation can occur in the annulus, and the casing 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 entering layer, so downhole gas separator should be considered. The conventional gas separator is composed of fluid entering part (such as perforating nipple), outer cylinder (such as a section of tubing with plug at the bottom) and liquid sealing pipe at the bottom of pump.
5. The displacement of the pump can be controlled by adjusting four parameters: plunger size, stroke length, pump stroke number and daily operation time. Due to the high cost of pumping equipment, the pump with inappropriate size is not usually replaced. The simplest way 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 pump stroke number. The matching problem of pump volume and well productivity can be realized by changing the daily operation time. The following devices can be used to control the operation time: air pumping controller, interval timer and percentage timer. If the air 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 cheap and easy to operate. The duration of pump stop should be short to the bottom hole production pressure rise no more than 10% of the reservoir pressure. The operator can measure the above acoustic wave and indicator for each well within 45min to determine the well productivity, downhole pump performance, downhole gas separator performance, sucker rod and beam pumping unit load and motor performance. Through the analysis of 45min, the operator can make the well production maximum and reduce the operation cost.
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