In oil exploration, oil wells are often accompanied by a certain amount of natural gas, water and solid particles. In order to reduce the well head back pressure, increase the crude oil output, improve the development benefit and achieve the objective of oil and gas confinement transportation, multi-phase mixed media such as oil and gas must be pressurized and transported with multiphase oil-gas pump. Single-screw pump can transport gas-liquid-solid multiphase medium, and can deliver pure gas medium in a short time, to achieve multiphase mixed transport. In the design of hybrid transmission system, the characteristics of mixed transmission medium and single-screw hybrid pump are fully analyzed to ensure the system is safe, reliable and scientific. Single screw oil and gas mixing pump working principle and characteristics Single screw pump work is the same outer surface of the rotor in the corresponding inner surface of the stator within the mesh to form a special contact line to separate the stator cavity, . When the rotor rotates according to a certain track, the seal line moves axially, and the stator cavity also moves axially, that is, displacement of the volume. At this moment, the seal line disappears at one end and a new seal line is generated at the other end, Push the media from one end to the other. Single-screw oil and gas pump due to the use of a good elastic rubber material of the stator, the rotor meshing with the need for a certain amount of interference, so that it produces a reliable seal. When the pump is working, the sealing line can effectively prevent the gas from passing, so as to achieve the purpose of conveying the gas. When the medium contains solid particles, if the solid particles are squeezed in the sealing line, the surface of the stator rubber is compressed due to the elastic effect of the rubber stator, The particles cross the seal line and the stator rubber rebounds back to its original shape so that the single screw pump can achieve the purpose of containing a trace amount of solid particles in the transport medium. Single-screw oil and gas mixing pump is suitable for corrosive media, gas-bearing media, sediment-containing solid particulate media and high-viscosity media. Gas content of up to 95%, medium viscosity up to 50000mPa · S, with a solid content of up to 60%, allowing the solid particle diameter ≤ 3.5 ~ 32mm, flow and speed is proportional to the low speed low flow to maintain pressure stability, Has a good regulatory performance, easy to achieve automation and control. Single screw heterogeneous transmission media main indicators Oil and gas ratio and moisture content Oil and gas multiphase transport medium is mainly composed of crude oil, natural gas and water, solid particles and other liquid, gaseous, solid components. In the development of oilfields, the indicators of oil and gas production that measure the production of oil wells are oil and gas ratio, moisture content and solid content. The oil-gas ratio and moisture content of different oil wells are different and vary greatly. Oil-gas ratio refers to the ratio of gas volume to crude oil volume of a hydrocarbon medium at standard atmospheric pressure. Gas under different pressures and temperatures, according to the gas equation to change its state; when not considering the temperature changes on its state changes, the gas volume changes inversely proportional to pressure changes. At the same time the pressure rises, some of the gas will be liquefied, whereas the liquefied gas will be gasified; and as its pressure changes, the amount of gas dissolved in the liquid will also change. When the oil and gas are mixed and transported, the pressure in the sucked-in pipe of the pump suction chamber is usually higher than the atmospheric pressure, and the gas in the medium has been compressed. At this moment, the medium-gas ratio at a specific gas pressure can no longer reflect the actual operation state of the pump . Moisture content refers to the mass percentage of anti-referring to water, nor does it reflect the actual operating status of the pump. In order to reflect the mixed liquid into the pump, gas ratio, I introduced the concept of liquid into the rate. Into the liquid rate Into the liquid rate is the medium into the pump, the liquid phase of the composition of the amount of traffic accounted for the percentage, here refers to the volume ratio. With the concept of liquid rate, no matter what the ratio of oil to gas, the amount of water contained in the liquid, how much gas is compressed, regardless of the amount of solid particles in the medium, with the liquid rate basically reflects the pump operation situation. According to the preliminary analysis of the test and the operation data of the oilfield, the liquid inlet rate is not less than 5%, and the single screw pump can work normally. 5% of the liquid will be the relative movement of the rotor and stator friction heat generated away, but also on the rotor and stator meshing surface play a role in lubrication, to ensure the normal operation of the screw pump. Mixed transportation design should pay attention to the problem Continuous supply of liquid media in the production of oil wells in the production of unstable state of the gas may be high for some time, while the liquid content is high for another period of time, so the use of Single-screw pump to do oil and gas mixed transport, in order to prevent the pump in the delivery of liquid and gas, mixed liquid process, a period of liquid flow, resulting in stator heat due to friction so that the stator rubber temperature, rubber aging, reduce The service life of the stator, the medium into the single-screw pump cavity try to use the uniform mixing of liquid and gas in the crude oil to ensure continuous supply of liquid medium to the pump. A, at the same time open the oil field block in the multi-well, oil and gas wells complement each other, so that into the single-screw pump medium as uniform as possible. B, before the pump pipeline buffer tank added, in the buffer tank to store a certain amount of crude oil, and a set of current limiting device to the mixed pump to supply a certain amount of crude oil. This no matter how well the gas content changes, can ensure the minimum rate of liquid, so that mixed pump to work properly. In the oil pipeline additional flow limiting device, the flow should be mixed pump flow 1/20 quantitative pump, with a single screw pump effect will be better, the use of time should also control the start and stop. C, after the pump line back to the oil tank, the tank with a current limiting device part of the liquid back to the mixed pump inlet to ensure that the pump into the oil and gas rate, the hybrid pump to work properly. Flow control device can throttle flow control, single screw pump can also be used to control the flow. The program due to the return part of the liquid, will reduce system efficiency. When the delivery flow is large, the use of multiple pumps in parallel delivery, we must pay attention to the symmetrical arrangement of the suction pipe to ensure that the medium into the single screw pump as evenly distributed to prevent bias current. Running in series When the transmission distance is far, the pump pressure is high, you can use more than one series operation. Due to the compressibility of the gas, the pump flow at all levels should be based on the ratio of oil to gas, the pressure of the manifold, the pressure of the mixed pipeline, and the pressure distribution among the pumps. In order to coordinate all levels of pumps can work properly, we must take the pressure of the pressure points automatically adjust the pump speed, adjust the pump flow, to achieve the purpose of high-pressure oil and gas mixture. Mixed pressure pump problems Because the mixed transmission system, mixed pump suction chamber not only to withstand oil well pipe back pressure, may also have to withstand the outlet pressure or pressure on the previous stage pump (Figure 1). When the delivery is switched by pipeline delivery to mixed delivery pump or delivered by mixed delivery pump to direct delivery, the suction and delivery ends of the pump are exposed to the pressure of the oil and gas mixing line when the valve is switched over. Therefore, the suction chamber must be able to have sufficient pressure capacity, usually to withstand the discharge pressure. Figure 1 Schematic diagram of pipeline direct transmission and mixed transmission Anti-inversion problem of mixed transmission pump After the hybrid transmission pump is operated in the process system, a certain pressure difference is generated between the pump and the pipeline. When the pump stop valve is not closed, there may be a reversal of the pump. Because most of the fluid in the oil-gas mixed transportation is gas, the flow resistance is small and the flow velocity is fast, which causes the pump to reverse over the rated speed, causing a speeding phenomenon and being prone to accidents. In the design process, should take appropriate measures to prevent this from happening. Can be installed in the pump outlet check valve to prevent reverse flow of fluid, this method is the most simple and practical and reliable; can also be used with brake motor. Prevent the over-pressure operation of single-screw pump General single-screw pump delivery of the nature of the media, the state is more complex, may cause congestion in the pipeline. Because the single screw pump is a positive displacement pump, when the blockage or human error, it will cause the pump overpressure, it is easy to damage its components. To prevent damage to the pump, a safety valve must be fitted between the discharge pipe of the pump and the suction pipe. Pressure outlet can also be installed in the pipeline relay, the pump exceeds the rated pressure automatically stop the pump. Single screw pump oil and gas mixing application example Figure 2 oil and gas mixing system Figure 2 is an oil field single screw pump oil and gas mixing application examples. In the mixed transmission system, two pumps are connected in parallel and the piping is symmetrically arranged; the pressure transmission signal of the inlet pipeline is sent to the electric control cabinet, and the pump displacement is regulated by the frequency converter to control the pump inlet constant pressure; the pump outlet pressure relay signal is sent To the control cabinet to achieve overpressure automatic alarm, automatic pump stop; pump outlet single-flow valve to prevent media backflow and mixed pump reverse role. Pump to ensure uninterrupted pump before the pump, the buffer tank to play a separate role, the separation of natural gas can also be used as heating furnace fuel. In the actual design of single screw pump oil and gas mixing process, according to the specific circumstances of the oil region, a comprehensive analysis of oil and gas mixing capacity, oil and gas production, oil and gas ratio, oil recovery, transmission distance and many other factors, many investigations and studies Comparison of programs, select the appropriate hybrid pump type, to develop a reasonable process layout, in order to achieve safe, scientific, reliable and economical operation of oil and gas mixed transportation.
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