• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method of controlling an electric submersible pump, comprising: a) monitoring the pressure at the suction and discharge of the pump; b) calculating the pressure difference between the discharge and suction pressure; and c) controlling the pump to maintain a constant pressure difference between the discharge and suction pressure.
    公开号:AU2013226203A1
    申请号:U2013226203
    申请日:2013-02-27
    公开日:2014-08-21
    发明作者:Lissett BARRIOS；David Earl HUGG
    申请人:Shell Internationale Research Maatschappij BV；
    IPC主号:F04D15-00
    专利说明:
    WO 2013/130524 PCT/US2013/027908 METHOD OF CONTROLLING AN ELECTRIC SUBMERSIBLE PUMP Cross-Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 61/605,795, 5 filed March 2, 2012, which is incorporated herein by reference. Field of the Invention The invention relates to a method of controlling an electric submersible pump located in a subsea caisson. Background 10 Electric submersible pumps are used in deepwater oil and gas production settings to provide artificial lift such that the oil and gas can be raised to the surface for further processing, storage and/or transport. During fluid property changes of the oil/gas mixture and/or introduction of water into the pump, large swings in pump operation can occur. These swings in pump operation can result in increased downtime, damage to the 15 pump components, seals and motor and decreased pump longevity. These problems are often encountered during startup of the pump when the fluids in and around the pump suction side have been allowed time to separate into distinct phases. For example, a separate water phase, gas/liquid phase and hot oil phase may be encountered in the electric submersible pump during startup. 20 Summary of the Invention The invention provides a method of controlling an electric submersible pump, comprising: a) monitoring the pressure at the suction and discharge of the pump; b) calculating the pressure difference between the discharge and suction pressure; and c) controlling the pump to maintain a constant pressure difference between the discharge and 25 suction pressure. The invention further provides a method of starting up an electric submersible pump, comprising: a) starting the pump on differential pressure control, comprising: i) monitoring the pressure at the suction and discharge of the pump; ii) calculating the pressure difference between the discharge and suction pressure; and iii) controlling the pump to maintain a 30 constant pressure difference between the discharge and suction pressure; and b) switching the pump control to pressure control, comprising: i) monitoring the pressure at the top of the caisson; and ii) controlling the pump to maintain a constant pressure at the caisson. 1 WO 2013/130524 PCT/US2013/027908 The invention also provides a method of controlling an electric submersible pump, comprising: a) monitoring the pressure at the caisson top; b) switching the pump control to differential pressure control during the start-up phase when fluid density inside the pump is changing; and c) switching the pump control to pressure control when the system has 5 stabilized in a specified operational pressure range. In certain embodiments, the method may further comprise: d) during steady operation, switching to constant pressure difference control automatically when an instability is detected, comprising: i) monitoring a performance variable that indicates the stability of the caisson operation; and ii) switching the control automatically to constant pressure difference control when the performance variable 10 exceeds a threshold value. Brief Description of the Drawings Figure 1 depicts an embodiment of the electric submersible pump showing the different fluid phases present on startup. Detailed Description 15 Electric submersible pumps are designed to operate in a range of conditions, but they are not designed for large pressure swings that can occur when the fluids passing through the pump change significantly. For example, slugs of water, changing oil/gas ratios and rapid changing of distinct fluid phases passing through the pump cause rapid swings in pressure as the pump operation characteristics vary with different fluid densities. These pressure swings 20 can cause damage to pump components and is believed to be at least a contributing factor of current electrical failures of electric submersible pumps in the field. The speed of an electrical submersible pump may be set via a Variable Frequency Drive (VFD); the speed of the pump may be directly-related to the frequency. Caisson pressure may be controlled by manipulation of the demand to the VFD. Manipulating the 25 electric submersible pump based on caisson pressure is normally satisfactory, but does not provide a rapid response during changing fluid conditions. The invention provides an alternate process control scheme that can be used to more effectively manipulate the electric submersible pump during startup and when fluid properties are rapidly changing. This process control scheme is referred to as constant boost mode 30 because it manipulates the pump speed based on the differential pressure across the pump. The differential pressure is calculated as the difference between the discharge pressure and the suction pressure of the pump. 2 WO 2013/130524 PCT/US2013/027908 Manipulating the pump in constant boost mode provides a more rapid response to fluctuations in fluid density to avoid instabilities on the system. One example of the issues encountered during startup is described further. When starting up an electric submersible pump located in a subsea caisson, the fluid phase that is 5 typically in the pump is an oil/gas mixture. As the pump starts up, the oil/gas mixture is pumped out the discharge and after some time, a water phase that has separated from the oil/gas mixture reaches the pump suction. The water is pumped and then another oil/gas phase is encountered. Then a hot oil phase is passed through the pump while the wells are ramped up and start producing and this is followed by the oil/gas mixture being produced 10 from the field. With each change in phases, the density changes; increases with water, decreases with oil/gas, increases with hot oil and decreases with field oil. Figure 1 depicts electric submersible pump system 100. Electric submersible pump system 100 may comprise a pump 110 and a shroud 120 surrounded by a caisson 130. Electric submersible pump system 100 may further comprise an inlet 101, a gas outlet 102, 15 and a liquid outlet 103. In certain embodiments, fluid within the pump may be an oil/gas mixture. A separate water phase may be located at the bottom of the caisson and an additional oil/gas phase is floating on the water phase outside of the shroud. After these phases have been pumped out, a new oil/gas mixture from the formation is pumped through the pump. 20 Once the pump has started up manually, the system is switched to caisson pressure control. In the alternative, the pump can be switched to constant boost control if slugs of water or other distinct phases are encountered as observed by pressure swings in the pump during operation. The constant boost mode will help the pump through the phase changes and the 25 pump can then be returned to caisson pressure control when system is in stable operation. In one embodiment, the differential pressure control is used to manipulate the electric submersible pump during startup and at any time during operation when the fluid density in the Caisson changes abruptly. As the caisson pressure is brought back into a more stable condition by controlling the differential pressure control, the pump can be switched back to 30 manipulation via caisson pressure control. The stability of the pressure can be detected by comparing the differential pressure in the Caisson to the last measured differential pressure or to a running average of a series of 3 WO 2013/130524 PCT/US2013/027908 differential pressure measurements. The specific characteristics of a stable system with regards to differential pressure should be determined based on the specific characteristics of the formation and the performance characteristics of the electric submersible pump. The differential pressure control scheme described herein provides a more rapid 5 response to fluctuations in pressure caused by changing fluid density, especially those encountered during startup. 10 4
    权利要求:
    Claims (8)
    [1] 1. A method of controlling an electric submersible pump, comprising: a. monitoring the pressure at the suction and discharge of the pump; 5 b. calculating the pressure difference between the discharge and suction pressure; and c. controlling the pump to maintain a constant pressure difference between the discharge and suction pressure.
    [2] 2. The method of claim 1 wherein the electric submersible pump is located in a subsea 10 caisson below the seafloor.
    [3] 3. The method of claim 1 wherein the electric submersible pump comprises a pump and a shroud.
    [4] 4. A method of starting up an electric submersible pump during start up, comprising: a. starting the pump on constant boost control, comprising: 15 i. monitoring the pressure at the suction and discharge of the pump; ii. calculating the pressure difference between the discharge and suction pressure; and iii. controlling the pump to maintain a constant pressure difference between the discharge and suction pressure; and 20 b. switching the constant boost control to pressure control, comprising: i. monitoring the pressure at the caisson top; and ii. controlling the pump to maintain a constant pressure at the caisson top.
    [5] 5. The method of claim 4 wherein the switching the constant boost control to pressure control is carried out by operator intervention. 25
    [6] 6. A method of controlling an electric submersible pump during operation, comprising: a. monitoring the pressure at the caisson top; b. switching the pressure control to constant boost control when the pressure goes outside of a determined operational pressure range during operation; and c. switching the constant boost control to pressure control when the pressure has 30 stabilized inside of the determined operational pressure range. 5 WO 2013/130524 PCT/US2013/027908
    [7] 7. The method of claim 6 wherein the switching the constant boost control to pressure control is carried out by operator intervention.
    [8] 8. The method of claim 6 further comprising carrying out steps b) and c) repeatedly as the pressure goes outside of the range and then is stabilized inside of the range. 5 6
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    同族专利:
    公开号 | 公开日
    GB2512555A|2014-10-01|
    AU2013226203B2|2016-04-07|
    MY175543A|2020-07-01|
    NO20141029A1|2014-08-22|
    GB201413294D0|2014-09-10|
    WO2013130524A1|2013-09-06|
    CN104160156A|2014-11-19|
    CN104160156B|2016-07-13|
    US20150017024A1|2015-01-15|
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    法律状态:
    2016-08-04| FGA| Letters patent sealed or granted (standard patent)|
    2021-09-23| MK14| Patent ceased section 143(a) (annual fees not paid) or expired|
    优先权:
    申请号 | 申请日 | 专利标题
    US201261605795P| true| 2012-03-02|2012-03-02||
    US61/605,795||2012-03-02||
    PCT/US2013/027908|WO2013130524A1|2012-03-02|2013-02-27|Method of controlling an electric submersible pump|
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