Compared with other types of pumping equipment, an important advantage of hydraulic piston pump is high efficiency, and its efficiency decreases with the decrease of dynamic level of oil well. The total efficiency of the hydraulic piston pump can reach 57% to 68% in the middle and deep wells. The basic working parameters of hydraulic piston pump, the displacement and pressure head can be adjusted smoothly in a large range, and the efficiency has not changed much. This is also the characteristic of other pumping units. The free installation hydraulic piston pump can make use of the power liquid to start and lower the operation, make the lifting operation mechanized, not only can greatly reduce the heavy manual labor, but also can reduce the time of stopping well, increase the output of crude oil, extend the life of tubing and reduce the cost of well construction. The free installation hydraulic piston pump needs only one worker, and it rises from 2000 m deep to the wellhead by power fluid. It generally needs only 30~60 min, and the 25~35 min is only needed. The main working parts of the hydraulic piston pump are easy to be standardized, and the use of the hydraulic piston pump is easy to realize the automation of the field.
Hydraulic piston pumps are especially suitable for the exploitation of the following oil wells.
(1) exploitation of deep and ultra deep wells
The hydraulic piston pump can work efficiently in deep and ultra deep wells. With the decrease of the moving surface of the oil well, the change of displacement and efficiency is not significant.
(2) mining of directional wells
The hydraulic piston pump is also very effective in the directional well mining, even when the angle of the well is up to 70° it is not difficult to work and operate under the condition of the well slope. Because of the compact and balanced ground equipment of the hydraulic piston pump, the hydraulic piston pump is suitable for the offshore oil well mining of the fixed platform or Zhanqiao. Offshore oil wells usually form a well group of 8~20 wells. Therefore, the surface equipment of hydraulic piston pump can be centrally driven, with simple maintenance and less investment, and the use of special power liquid closed system can solve the problem of safety and fire protection of offshore oil well exploitation.
(3) mining of small well wells
At present, a diameter of 140 mm casing has been replaced with a diameter of 168 mm bushing, and a diameter of 114 mm or smaller casing is being developed. This can speed up drilling and reduce investment. The hydraulic piston pump is technically effective in the case of smaller borehole.
(4) the exploitation of heavy oil
When the viscosity of the crude oil is very high, it is sometimes impossible to use a sucker rod pumping unit, and the efficiency is low by using the electric submersible pump. When the hydraulic piston pump is used, the crude oil can be heated by using the thermo dynamic liquid, so that the viscosity of the crude oil can be reduced, and other methods can also be used to reduce the viscosity of the crude oil. Therefore, it is very effective for the hydraulic piston pump to extract heavy oil.
(5) mining of multiple wax wells
Practice has proved that the mining wax wells with hydraulic piston pump, oil pipe wall wax deposition found little. This is because the crude oil in the well has been mixed with the waste power liquid at the outlet of the hydraulic piston downhole unit, reducing the volume and wax content of the liquid volume per unit volume, and the effect of wax is reduced. The effect of wax can be completely eliminated by using hot fluid or adding wax removing agent into the power liquid.
Hydraulic piston pump is required to double down wells defects (refer to the fixed insertion type and pipe type, parallel pipe free) on the one hand it increases the metal consumption and equipment investment, improve the underground repair labor and maintenance costs; on the other hand it restricts underground unit size, complicated structure. In order to solve this problem, the casing fixed or casing freestyle, which adopts the single column tubing packer scheme. However, the precondition of the above scheme is to ensure the straight and sealing of the casing string, and at the same time, the ratio of gas to oil is low or the dynamic level is high, so the large submergence is allowed. If these conditions are not available, we can consider the use of double parallel tubing string, that is, parallel tube free form, which can reduce the quality of the equipment, but it is limited in displacement. Hydraulic piston pumps should be specially prepared for dynamic fluid in some oil areas, especially in the mining of loose sandstone reservoirs. In the cold weather in winter, the operation of the ground equipment and the pipeline of the hydraulic piston pump is difficult. The depth of the pump under the hydraulic piston pump is limited by the strength of the tubing. The above shortcomings can be overcome after taking corresponding measures.
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