At present, most domestic and foreign pumping wells use tube pumps. The fixed valve in these pumps is unidirectional, allowing crude oil from the formation to flow into the pump through the fixed valve and then be lifted to the surface during the pumping process. However, it has been observed that the liquid in the well often passes through the fixed valve, which can lead to issues over time. On one hand, the presence of impurities in the liquid may prevent the fixed valve from closing properly, leaving it permanently open. On the other hand, the liquid entering the pump through the fixed valve can cause wear or erosion, leading to failure of the valve. If the single fixed valve malfunctions, non-periodic pumping operations are required, increasing downtime and maintenance costs.
To address this issue, researchers from the Tuha Oil Exploration and Development Headquarters' underground technical operations company collaborated with the Georgia National 12 Block Oil Field workshop. They developed a double fixed-valve pump, known as the reefable double fixed-valve pump. This improved design was successfully applied in the 12th block of the national oil fields in Georgia, significantly enhancing operational efficiency and reducing maintenance requirements.
**Technical Analysis**
**1. Structure**
The double fixed-valve pump is an upgraded version of a conventional pump, incorporating a fishing-type fixed valve and a salvager. From top to bottom, the components include a fishing claw (connected to the pump piston via a threaded connection), a fishing head (attached to the fixed valve using a threaded joint), a circlip, a conversion joint, a secondary sealing ring, a fillable fixed valve cover, a valve ball, a ball seat, and a pressure cap.
The cylindrical fishing claw features two opposite hook-shaped grooves, while the fishing head is welded to a cylindrical crossbar. The width of the hook groove is slightly larger than the diameter of the crossbar, allowing the crossbar to be inserted or removed, enabling the connection or separation of the fishing claw and fishing head.
**2. Working Principle**
The fillable fixed valve is manually set in place by the fishing claw, supported by the upper section of the pump. Once loaded with 419–918 units, the two secondary sealing rings compress against a steel ring (with 60° and 30° chamfers), creating a tight seal between the rubber rings and the support short section. A card spring is also engaged, preventing upward movement of the body during operation. Meanwhile, the steel ring supports the circlip on the valve body, ensuring it cannot move downward, thus achieving both primary and secondary seals.
When the fixed valve is set, the lifting rod is suspended at its original position and rotated 1–2 revolutions to align the fishing head with the groove. This allows the salvage claw to disengage from the fishing head, freeing the valve for operation. Before pumping, the well must be assessed to determine the faulty parts. If the fixed valve fails, the tubing is deepened, reversed 1–2 times, and the fishing head is retrieved. Operators should closely monitor the pole’s movement; if it moves downward during rotation, it indicates a successful retrieval. After confirming the salvage, the failed valve is replaced with a new one.
If the parts above the fixed valve fail, the piston can be easily replaced without removing the entire pump. However, if the well requires inspection, the entire system must be pulled out.
**3. Main Technical Parameters**
(Not specified in the original text)
**4. Key Features**
(1) The reliable fishing fixed valve ensures the valve body remains securely seated on the support short section, preventing damage and ensuring continuous production.
(2) The valve is delivered to the setting position by the pump piston, and once set, it can be released and adjusted for operation. Installation does not require disassembling the pump, making it user-friendly and efficient.
(3) During pumping, impurities or wear can cause the valve to malfunction, reducing pump efficiency. With the reefable double fixed valve, such failures are minimized, lowering operating costs.
(4) Maintenance is simple—only the rubber seal and valve ball need replacement, reducing repair frequency and costs.
**Field Application**
Since July 2002, the sealable double fixed-valve pump has been used in 85 wells across the 12 blocks of the Georgia National Oil Field. During operation, one well experienced a 99% failure rate due to tubing obstruction, but the valve was reliably seated and recovered. All 85 wells were completed successfully on the first attempt. Previously, single fixed-valve pumps required frequent inspections whenever the valve failed. With the new design, the valve can be repaired without replacing the tubing, extending the inspection cycle and saving costs. According to statistics, the average inspection interval per well has increased by 0.18 times, resulting in a total cost savings of 175.18 million yuan in operational expenses.
In conclusion, the use of the double-fixed fishing gear pump ensures safe and reliable downhole operation, simplifies the pumping process, and significantly reduces maintenance and operational costs.
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