Abstract: Studying the internal pump flow field, especially the mixed-phase flow field, is the key point to improve the pump performance. For this purpose, the University of Petroleum (Beijing) developed a set of simulation test devices for a gas-liquid two-phase flow hydraulic pump. The device consists of a single-phase flow test device and a mixed-phase flow test device. The former can simulate various working conditions in the downhole well and flow state of liquid in the oil pump more accurately, the latter can simulate different oil-gas ratio. In order to quantitatively complete the transient measurement of the flow field without interfering with the flow field, the image processing results of the velocity vector and the curl field of the planar flow field are given to reveal the transient flow structure of the flow field. A high precision , Spatial resolution and fast dynamic response characteristics of particle imaging speed (PIV) advanced technology.
Oil pump is one of the main equipment in the process of oilfield development. Improving the performance of oil pump can effectively increase the output of crude oil in the oilfield and improve the economic benefits of oilfield development. At present, the development of the pump can be divided into the following three aspects.
(1) Based on the mechanics analysis, the mechanics description of the valve opening and falling process is made through the simplification of the movement conditions and the stress conditions.
(2) In accordance with the principle of functional design according to production needs, technical innovation should be carried out on the basis of the original pump structure, such as the development of anti-sanding card pump and anti-gas pumping heavy-duty oil pump;
(3) In order to study the efficiency of pumping oil pump and its influencing factors, the relevant laboratory tests and observations are carried out.
Such as Daqing Petroleum Institute pump energy consumption test research, the use of pressure sensors and displacement sensors to measure the pump import and export pressure curve, the pressure drop curve of the ball valve and the power diagram, loss and so on.
At the moment, the most fundamental problem with pump performance improvements - the pump flow field - is not covered yet. The key factor to solve the problem of pump valve's movement, reasonability of pump structure and its improvement is the state of flow field in the pump. Therefore, studying the internal flow field, especially the mixed phase flow field, is the key point to improve the pump performance . With PIV (particle image velocimetry) technology, LDV (Laser Doppler Flow Velocimetry) technology and ultrasound technology are maturing, people can use these advanced flow field test techniques to achieve the measurement without disturbing the flow field High-precision, there are already examples of the use of these advanced technologies in Canada to study the pump flow field, but no published results were found. Therefore, the use of PIV and other advanced technology to study the flow field within the pump to improve the structure of the pump is the general direction of development in the future. In view of this, the University of Petroleum (Beijing) Offshore Engineering Laboratory carried out a visualization of the internal flow field in the pump. Since there is no precedent in this respect, it is planned to proceed with the experiment first and put both theory and practice together.
Design of pump simulation test device
Pumping in the downhole working medium is not single-phase, so on-site work of pumping pump cavity flow field actual test more difficult. In order to save time and money, but also to test the flow field of pump cavity under normal circumstances, the pump simulation test device must have gas source and liquid source, as well as visualization of research conditions, and the flow rate can also be single Liquid and gas-liquid two-phase flow characteristics of the pump when the visual observation and recording, so the entire pump chamber should be transparent. In addition, due to the strong variation of the flow field, there should be a corresponding data acquisition and processing system. In order to observe the effect of pump stroke on the flow field, the rod drive system should be adjustable.
Structure design of simulation test device
In order to simulate the up-and-down reciprocation of plunger and polished rod of on-site oil pump, the proper power system must be selected. One solution is to reduce the on-site pumping system of ground power, that is, take the motor-driven donkey head drive. The disadvantage of this solution is the high cost, large area, not suitable for laboratory use. Another solution is to use the motor to drive the rope directly through the pulley rod and plunger up and down movement, but in order to ensure the balance of the system need to configure the balance weight, the other selection of micro-motor has difficulty. These two programs are unable to simulate the import and export pressure pump, pump flow can not be adjusted. To solve the above problems, I used hydraulic control system and pneumatic control system to achieve dynamic system simulation. Hydraulic control system is mainly to achieve reciprocating plunger up and down and control the pressure of import and export, pneumatic control system is to control the mixed-phase flow of intake. At the same time, the hydraulic control system is divided into two parts: the first part is the power cylinder hydraulic system, which is the main power source; the second most is the pump pressure compensation system, mainly used to control the pump import and export pressure And for the pump oil. Here are the three parts to be introduced.
Power cylinder hydraulic system
Power cylinder hydraulic system mainly by the power cylinder, travel switch, two four-way solenoid valve, relief valve, pump and governor valve composition, the process shown in Figure 1.
Figure 1 power cylinder hydraulic system flow chart
1-power cylinder; 2-position 4-way solenoid valve; 3-speed valve; 4-relief valve; 5- oil pump; 6,7-travel switch
How it works: When the power oil pump to the upper end of the fuel tank, the drive piston down to drive the polished rod down, when the light rod touches the limit switch 6, the two four-way solenoid valve to reverse the power pump to start The lower end of the power cylinder is supplied with oil to drive the piston to move upward so as to drive the polished rod to move upwards. When the polished rod touches the limit switch 7, the 2-position electromagnetic reversing valve is reversed to resume the next stroke. Speed ​​control valve piston speed can be adjusted to change the stroke, the relief valve can adjust the pressure inside the power cylinder, changing the plunger drive.
2. Suction pump pressure compensation system
Suction pump pressure compensation system mainly by the fuel tank, pump, sequence valve, accumulator, pump, pressure gauge, pressure tank and relief valve composition, the process shown in Figure 2.
Figure 2 pumping pump pressure compensation system flow chart
1 oil tank 2 oil pump 3 sequence valve 4 accumulator 5 oil pump 6 pressure gauge 7 pressure tank 8 accumulator 9 relief valve
Working principle: the pump is always in working condition, the relief valve is adjusted to a certain pressure, when the pump inlet pressure exceeds the regulation pressure, the relief valve overflow, the inlet pressure decreases; when the inlet pressure is too low, the pump to the pressure tank Oil, so that the import pressure rose to regulate the pressure. The role of two accumulators is to avoid the import and export pump pressure fluctuations, to ensure that the import and export pump pressure to meet operating conditions.
3. Pneumatic control system
Pneumatic control system consists of air pump, gas flow meter, solenoid switch, check valve and travel switch, the process shown in Figure 3.
Figure 3 pneumatic control system flow chart
1-gas pump; 2-gas flow meter; 3-electromagnetic switch; 4-way valve; 5- pump; 6-stroke switch
Working principle: When the pump to do the stroke movement, the electromagnetic switch is open, the gas through the one-way valve into the pump, when the polished rod contacts the on-stroke switch, the electromagnetic switch is off, the gas barrier, then pumping down stroke . When the polished rod touches the down stroke switch again, the electromagnetic switch is opened and the gas path is opened, and the gas is supplied to the oil pump again.
Simulation test device features
The simulation test device is divided into two major parts: the first part is a single-phase flow test device, which is mainly composed of a power cylinder, a plexiglass pump cylinder, a plunger and a hydraulic control system, and is the core part of a pump simulation test device. Outstanding features is the use of hydraulic control system to drive the plunger up and down reciprocating motion, with a stable stroke, rapid commutation, complete simulation of underground conditions, etc., can more accurately simulate the underground working conditions and liquid pumping within the pump status. The second most are mixed-phase flow test device, mainly by the pump, gas flow meter, electromagnetic switch and water tank. The characteristics of this multiphase flow device are simple and easy to use, relatively perfect function, can simulate different oil-gas ratio, and the intake air is completely controlled by the electromagnetic switch driven by the travel switch, which can more accurately simulate various working conditions in the well. In addition, in order to facilitate observation and testing, plunger and pump cylinder made of plexiglass, so as to achieve the purpose of using this test device to observe and test the pump flow field. The test device is finally selected through the optimization and demonstration of different schemes. The structure is light, the function is complete, the control system is simple and reliable, and the operation is convenient. The test device can well simulate the operation of the pump and the various working conditions in the pump. This test device is an innovative simulation of the pump test device, compared with similar simulation devices at home and abroad, both in terms of cost or overall performance has its own unique characteristics.
Image acquisition and processing system
In order to quantitatively complete the transient measurement of the flow field without interfering with the flow field and to give the image processing results of the velocity vector and the curl field of the planar flow field to reveal the transient flow structure of the flow field, Particle imaging velocity (PIV) technology. Particle imaging velocimetry has the characteristics of high precision, high spatial resolution and fast dynamic response. It is the most advanced technique for measuring complex flow fields. It can freeze the flow field at some point, revealing the hidden turbulent flow structure. The measurement results are of sufficient precision to subtract the large average velocity from a vector and thus give flow parameters that fully reflect the flow field, such as average velocity, pulsation velocity, and vortex, respectively Test technology does not have.
PIV image acquisition and processing system configuration shown in Figure 4.
Figure 4 PIV system's original configuration
Generally speaking, a complete PIV system can be divided into three major parts: the first is the lighting system whose function is to generate the light source; the second is the recording system whose function is to generate a double (multiple) exposure image of the particle flow; Third, the query system, its function is to extract and display the image of the velocity field and other flow parameters.
The lighting system in the simulation experiment device uses a 10W neon laser, the recording system uses a video recorder, and the inquiry system uses the PIV image processing software developed by the University of Petroleum (Beijing).
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