Hollow sucker rod is a special oil pumping rod designed specially for high freezing point, high viscosity and high wax oil extraction. It is combined with threaded joints, sealing and rod body. The rod body is made of seamless steel pipe, and the screw thread joint is connected with the rod body through friction welding and heat treatment. Because the hollow sucker rod is designed on the surface of the bearing, the joint is more reliable. Design of a hollow structure can be injected into the hot oil or steam, it can also be used for the operation of heating cable. The hollow sucker rod reduces the viscosity of oil and wax deposition, and improves the efficiency of the pump. There is a plastic cap protects the thread of the hollow sucker rod and the plastic cap can also be painted with color. The hollow sucker rod also saves space of the metal pallet packaging, which is convenient for transportation.
Except with common sucker rod transmission power, hollow sucker rod can also reduce the viscosity of crude oil, anti-corrosion insulation, control of the paraffin wax, to improve the physical properties of the shaft, so as to improve the pump efficiency; The anti torque ability of the hollow sucker rod is better than that of the traditional sucker rod, which can be used to drive the downhole screw pump, and the hollow sucker rod shaft is very convenient to be installed on the controller.
In view of the problems in the crude oil extraction process, such as: crude oil is difficult to lift, the sucker rod load overweight, downward difficult, pumping oil airborne load increased and so on, hollow sucker rod electric heating device was successfully developed.
The device is to make the cable which through the hollow rod to the bottom of the well shorted connected to the sucker rod. The circuit is composed of a cable and a hollow rod. When the cable and the hollow rod simultaneously pass through the positive and negative alternating current, the hollow rod is integrally heated due to the skin effect of the current. The heat energy produced by electric heating is used to heat the crude oil in the oil pipe, so as to improve the fluidity of the crude oil. Effective solution to a variety of technical problems is to achieve the purpose of increasing production and efficiency of oil wells.
When there is an alternating current or electromagnetic field in the conductor, the current in the conductor will be concentrated on the surface of the conductor. The resistance of the wire increases and the loss power is increased, which is called the skin effect.
As the temperature of crude oil in the wellbore is increased, the viscosity of crude oil drops significantly, the oil well lifting resistance is obviously reduced, and the pump efficiency can be increased by more than 20%. At the same time, due to the acceleration of the oil well, the production of oil well is generally improved. The production efficiency of oil well is increased, and the production cycle is prolonged. The installation and management of the device is convenient, and the comprehensive economic benefit is very significant.
Hollow sucker rod also has some problems:
In order to ensure that there is sufficient contact area, the hollow sucker rod will use too many joints, resulting in the improvement of the cost. In the threaded connection, due to the stress concentration and the generation of the prestressing force, the root of the external screw thread is easy to break. Due to the friction motion of the vibration, the neutral point and the wall surface, the trip performance of the joint of the hollow sucker rod is poor.The sealing performance of the joint of the hollow sucker rod is poor. It is difficult to ensure the strength safety of the joints due to the limitation of the geometrical size.
To sum up, the selection of sucker rod is very learned. According to the actual situation and needs to choose the appropriate sucker rod to better finish the work.
