What sucker rod pump is suitable for heavy oil wells with sand?
With the continuous improvement of oil recovery technology, some special oil reservoirs have attracted the attention of oil workers. As heavy oil accounts for a large proportion of petroleum resources, how to extract heavy oil to meet people’s increasing demand for oil has become a problem.
Thermal oil recovery is a common method for heavy oil recovery. Thermal oil recovery uses some measures to increase the temperature of the oil layer, reduce the viscosity of the heavy oil, and make the heavy oil easy to flow, so that the heavy oil can be produced. The main methods include steam huff and puff, steam flooding, burning oil layer, hot water flooding, etc.
The sucker rod pump, an important machine in oil exploration and extraction, normally works in a heavy oil and sand environment in which severe abrasion and erosion occur, especially on oil-well tubings. To improve the service life, DLC coatings with different thicknesses are fabricated on the oil-well tubings and the mechanical, tribological, and anti-corrosion properties are investigated. The results show that the thickness can be compromised with adhesion due to the low stress induced by alternate implantation and deposition at the pulsed high-voltage bias. Compared to severe abrasion of the carbonitriding AISI 1045 oil-well tubing, the thick DLC coatings have good anti-abrasion properties in the heavy oil and sand environment. Moreover, excellent erosion resistance is observed from the DLC-coated samples as exemplified by the small corrosion current density and high corrosion potential. The tests conducted in both simulated and practical working conditions reveal that the service life of the oil-well tubing is significantly improved.
Multilateral wells with limited sand production are proposed to produce offshore heavy oil reservoirs. This technique was studied through lab experiments and numerical simulation. Permeability increases with sand production and formation fines of less than 39 μm diameters are the main fines that jam pore throats and influence permeability the most. For a given total length of branches, productivity slightly decreased with increasing branches, suggesting that the number of branches should not be very higher, two or three are better; and productivity increased with the increase of branch angles, but the increase of productivity decreases. Field test was carried out in NB35-2 oil field and the individual layer deliverability of a multilateral well with limited sand production is three times the multilayer production of the common deviated well.
The oil well pump is downhole equipment for pumping oil. The liquid that is sucked contains sand, wax, water, gas and corrosive substances. It works downhole from hundreds of meters to thousands of meters, and the internal pressure of the pump may be as high as 10 MPa or more. Therefore, its working environment is complicated and the conditions are harsh, and the pumping performance directly affects the oil well production. Therefore, the oil well pump should generally meet the following requirements:
(1) Simple structure, high strength, good quality, and reliable sealing of the connecting part;
(2) The manufacturing material has good wear resistance and corrosion resistance, and has a long service life;
(3) The specifications and types can meet the needs of oil well drainage, and have strong adaptability;
(4) Easy to get up and down;
(5) Sand and gas control should be considered in the structure, and necessary auxiliary equipment should be provided.
At present, heavy oil wells mostly use tandem downhole pumps ( hydraulic feedback pumps) or multifunctional pumps to produce heavy oil. When steam injection in downhole is needed to reduce the viscosity, the plunger must be lifted out of the pump barrel. During steam injection, the work rack is not used, but the pumping unit is used to lift the plunger multiple times to complete the work of raising the plunger. In addition, due to the special structure of the tandem pump, its displacement is smaller than that of the conventional pump with the same plunger, which is not conducive to the discharge of a large liquid volume after steam injection and pumping, which affects the effect of spit mining. The use of multi-function pumps requires repeated operations many times, which is laborious.
In order to improve the recovery efficiency of heavy oil wells, Sanjack Group has developed a long displacement plunger injection and production pump with large displacement and convenient operation. The design consists of pump barrel assembly, plunger assembly, standing valve assembly and pump tube. The structure diagram is as follows:
|Steam Injection Hole
|Standing Valve Assembly
This tubing pump barrel of the new pump uses a short type and the plunger is a long type. One or more steam injection holes are opened on the pump barrel. When the steam injection operation, the plunger is lowered to the bottom dead point, the top of the plunger drops below the steam injection hole and the steam injection hole connects the inside and the outside of the tubing. Thus, the hot steam enters the annular sealed space of the tubing and the casing through the steam injection hole, and is injected into the downhole. When the steam injection is completed, the plunger is lifted up, the plunger seals the steam injection hole and the sucker rod pump can pump oil normally.
This new type of oil pump has a reasonable design structure, large displacement, and convenient operation, and is especially suitable for the production of heavy oil wells with sand.