During the operation of the oil sucker rod tubing pump, “air lock” is a common and easily overlooked failure. Once it occurs, it will cause the pump body's oil absorption and exhaust efficiency to plummet, and even cause equipment idling and wear. The so-called air lock refers to the phenomenon that after underground gas (such as natural gas and dissolved gas) enters the pump chamber of the oil sucker rod tubing pump, it occupies the effective space of the pump chamber due to the strong compression of the gas and the difficulty of discharging it, hindering the normal inhalation and lifting of crude oil. Timely and scientific removal of the air lock from the pump body associated with the pump rod is the key to ensuring the stable operation of the oil sucker rod tubing pump, which can be achieved in three steps: “Judgment-treatment-prevention”.
First determine: the typical characteristics and causes of air locks：
If you want to effectively remove the air lock, you first need to accurately judge the fault. When an air lock occurs, the oil sucker rod tubing pump will show obvious characteristics: the ground pumping unit is operating normally, but the oil output from the wellhead is significantly reduced or even cut off; The load of the pumping rod fluctuates abnormally, and the load of the donkey head suspension point rises and falls; The pointer of the wellhead pressure gauge beats frequently, and the pressure value is unstable.
There are three main causes of air locks: one is the high gas content of the oil layer. When the crude oil is extracted from the oil layer to the pump chamber, the gas dissolved in the crude oil escapes due to reduced pressure and accumulates at the top of the pump chamber; The second is the insufficient depth of the pump body, and the pump suction port is not completely sunk in the crude oil, resulting in the existence of a gas channel between the wellhead and the pump chamber; The third is that the fixed valve or swimming valve of the oil sucker rod tubing pump is not tightly sealed, and the gas enters the pump chamber in reverse from the valve group gap, gradually forming an air lock.
Reprocessing: Four practical methods to remove the air lock
For air locks of different causes, corresponding treatment methods need to be used to quickly restore the oil sucker rod tubing pump function.
Method 1: Adjust the stroke of the pumping unit to promote gas discharge:
If the degree of air lock is light, the suction time of the pump chamber can be extended by reducing the number of strokes of the pumping unit (for example, from 6 times/min to 3-4 times/min), so that there is enough space for the gas to be discharged slowly with the crude oil.At the same time, observe the oil output situation and pressure changes at the wellhead. If the oil output gradually resumes within 30 minutes, the air lock has been initially released; Iif the effect is not good, it can be operated with a “jog pumping unit”-intermittent start and stop pumping unit, using pressure fluctuations to break the gas accumulation state.
Method 2: The wellhead is deflated and the gas is directly released：
When the air lock is triggered by the gas channel from the wellhead to the pump chamber, the gas can be released through the wellhead vent valve. After closing the wellhead production valve, slowly open the vent valve and observe the changes in the pressure gauge. When the pressure drops to a stable value (usually lower than the pressure of the oil layer 0.5-1MPa) and no gas continues to be discharged, close the vent valve, reopen the production valve, and start the pumping unit. This method needs to pay attention to controlling the venting speed, avoid splashing crude oil due to a sudden drop in pressure, and take safety precautions at the same time.
Method 3: Deepen the depth of the pump body to prevent gas inhalation：
If the air lock is due to insufficient sinking of the pump suction port, the pumping rod and oil pipe column need to be deepened through the workover equipment after shutdown, so that the depth of the pump suction port sinking in the crude oil is increased by 20-50 meters, to ensure that the pump chamber is always filled with crude oil, blocking the gas from entering the channel. After adjustment, start the pumping unit for trial operation. If the load of the pumping rod and column is stable and the oil output is normal, the air lock problem will be solved from the root cause.
Method 4: Replace the valve assembly parts and repair the sealing loopholes：
When the air lock is caused by the lax sealing of the valve group, the oil sucker rod tubing pump needs to be raised to check whether the sealing surface of the fixed valve and the swimming valve is worn or deformed. If the valve seat is found to be scratched or the valve ball is aging, replace the parts of the valve group of the same type in time, reassemble the pump body and go down into the well. After replacement, a sealing test is required to ensure that there is no gas leakage in the pump chamber, and then the pumping unit is started to run.
Post-prevention: daily maintenance reduces the occurrence of air locks
In order to avoid the recurrence of air locks, it is necessary to do a good job in the daily maintenance of oil sucker rod tubing pump: regularly check the sealing performance of the valve group and replace the vulnerable seals every 3 months; Adjust the sinking degree of the pump body according to the gas content of the oil layer, and the oil well with high gas content can appropriately deepen the depth of the pump; Establish an air lock monitoring mechanism, through the wellhead pressure sensor and the pumping unit load monitoring system, real-time early warning of the risk of air lock.
Although the air lock will temporarily affect the operation of the oil sucker rod tubing pump, as long as the scientific judgment and treatment methods are mastered, the efficiency of the equipment can be quickly restored. Tieling Dongsheng Petroleum Machinery Co., Ltd., which is deeply engaged in the field of oil sucker rod tubing pump, can not only provide pump body design with better anti-air lock performance (such as anti-air lock valve group structure), but also provide customers with technical guidance on air lock troubleshooting and handling to help long-term stable production of oil wells.