Embodiments of the invention generally relate to the field of submersible pumping systems, and more particularly, but not by way of limitation, to a system designed to produce fluids with a high gas fraction from subterranean wells that may also include significant volumes of liquid.
Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, the submersible pumping system includes a number of components, including one or more fluid filled electric motors coupled to one or more high performance pumps located above the motor. When energized, the motor provides torque to the pump, which pushes wellbore fluids to the surface through production tubing. Each of the components in a submersible pumping system must be engineered to withstand the inhospitable downhole environment.
Some reservoirs contain a higher volume of gaseous hydrocarbons than liquid hydrocarbons. In these reservoirs, it is desirable to install recovery systems that are designed to handle fluids with higher gas fractions. Prior art gas handling systems are generally effective at producing gaseous fluids, but tend to fail or perform poorly when the exposed to significant volumes of liquid. Many wells initially produce a higher volume of liquid or produce higher volumes of liquid on an intermittent basis. The sensitivity of prior art gas handling systems to liquids presents a significant problem in wells that produce predominantly gaseous hydrocarbons but that nonetheless produce liquids at start-up or on an intermittent basis. It is to these and other deficiencies in the prior art that the embodiments of present invention are directed.
In some embodiments, the present invention includes a fluid processor for use in a downhole pumping operation. The fluid processor includes a fluid processing stage, a nozzle stage and a gas compressor stage. The fluid processing stage may include an impeller and a diffuser. The nozzle stage may include a nozzle chamber and a variable metering member. The nozzle chamber is configured as a convergent-divergent nozzle and the variable metering member is configured for axial displacement within the convergent section to adjust the open cross-sectional area of the nozzle. The gas compressor stage includes one or more gas compressor turbines.
In another aspect, some embodiments include a method for producing fluid hydrocarbons from a subterranean wellbore, where the fluid hydrocarbons have a variable gas-to-liquid ratio. The includes the steps of measuring a first gas-to-liquid ratio of the fluid hydrocarbons with the sensor module; outputting a signal representative of the first gas-to-liquid ratio of the fluid hydrocarbons to a variable speed drive; and applying an electric current from the variable speed drive to the motor to cause the motor to operate at a first rotational speed. The method continues with the steps of measuring a second gas-to-liquid ration of the fluid hydrocarbons with the sensor module, where the second gas-to-liquid ratio is greater than the first gas-to-liquid ratio; outputting a signal representative of the second gas-to-liquid ratio of the fluid hydrocarbons to the variable speed drive; and applying an electric current from the variable speed drive to the motor to cause the motor to operate at a second rotational speed that is faster than the first rotational speed.
In accordance with an embodiment,
The pumping system 100 may include a fluid processor 108, a motor 110, a seal section 112, a sensor module 114, an electrical cable 116 and a variable speed drive 118. Although the pumping system 100 is primarily designed to pump petroleum products, it will be understood that embodiments of the present invention can also be used to move other fluids. It will also be understood that, although each of the components of the pumping system are primarily disclosed in a submersible application, some or all of these components can also be used in surface pumping operations.
The motor 110 may be an electric submersible motor that is provided power from the variable speed drive 118 on the surface by the electrical cable 114. When selectively energized, the motor 110 is configured to drive the fluid processor 108. The variable speed drive 118 controls the characteristics of the electricity supplied to the motor 110. In an embodiment, the motor 110 is a three-phase electric motor and the variable speed drive 118 controls the rotational speed of the motor by adjusting the frequency of the electric current supplied to the motor 110. Torque is transferred from the motor 110 to the fluid processor 108 through one or more shafts 120 (not shown in
In some embodiments, the seal section 112 is positioned above the motor 110 and below the fluid processor 108. In some embodiments, the seal section 112 isolates the motor 110 from wellbore fluids in the fluid processor 108. The seal section 112 also accommodates the expansion of liquid lubricant from the motor 110 resulting from thermal cycling.
The sensor module 114 is configured to measure a range of operational and environmental conditions and output signals representative of the measured conditions. In an embodiment, the sensor module 114 is configured to measure at least the following external parameters: wellbore temperature, wellbore pressure and the ratio of gas to liquid in the wellbore fluids (gas fraction). The sensor module 114 can be configured to measure at least the following internal parameters: motor temperature, pump intake pressure, pump discharge pressure, vibration, pump and motor rotational speed, and pump and motor torque. The sensor module 114 may be positioned within the pumping system 100 at a location that permits the measurement of upstream conditions, i.e., the measurement of fluid conditions approaching the pumping system 100. In the embodiment depicted in
In some embodiments, the fluid processor 108 is connected between the seal section 112 and the production tubing 102. The fluid processor 108 may include an intake 122 and a discharge 124. The fluid processor 108 is generally designed to produce wellbore fluids that have a predominately high gas fraction but that present significant volumes of liquid at start-up or on an intermittent basis. The fluid processor 108 includes turbomachinery components that are configured to increase the pressure of gas and liquid by converting mechanical energy into pressure head. When driven by the motor 110, the fluid processor 108 draws wellbore fluids into the intake 122, increases the pressure of the fluid and pushes the fluid through the discharge 124 into the production tubing 102.
Although only one of each component is of the pumping system 100 shown in
It will be noted that although the pumping system 100 is depicted in a vertical deployment in
Turning to
Turning to
Turning to
Turning to
The variable metering member 138 shown in
As shown in
Turning to
The operation of the fluid processor 108 is adjusted based on the condition of the fluid in the wellbore 104. Based on information provided by the sensor module 114 about the gas-to-liquid ration in the wellbore fluid, the variable speed drive 118 adjusts the electric current provided to the motor 110, which in turn, adjusts the rotational speed of the rotary components of the fluid processor 108. When the wellbore fluid exhibits a high liquid-to-gas ratio (above about 5% LVF), the motor 110 operates at a relatively low speed. At lower speeds, the fluid processing stage 126 is effective and pumps the high liquid-fraction fluid through the fluid processor 108. At these lower rotational speeds, the compressor stage 130 does not significantly increase or impede the flow of fluid through the fluid processor 108.
When the sensor module 114 detects the presence of wellbore fluids with a higher gas-to-liquid ratio, the variable speed drive 118 increases the rotational speed of the motor 110, which in turn, increases the rotational speed of the rotary components in the fluid processor 108. The higher rotational speed allows the compressor stage 130 to increase the pressure of the high gas fraction fluid. During operation, the nozzle stage 136 meters the flow of fluid into the compressor stage 130 and reduces the size of liquid droplets entrained in the fluid stream.
In some embodiments, the fluid processor 108 is operated in a low speed “pump” mode when the liquid fraction is above about 8%. When the liquid fraction is below about 8%, the speed of the fluid processor 108 can be increased to optimize the operation of the compressor stage 130. Thus, in some embodiments, the operation of the fluid processor 108 is adjusted automatically to optimize the movement of fluids depending on the gas-to-liquid ratio of the fluids. Although the sensor module 114 can be used to provide the gas and liquid composition information to control the operation of the fluid processor 108, it may also be desirable to control the operation of the fluid processor 108 based on the torque requirements of the motor 110. An increase in torque demands may signal the processing of fluids with higher liquid-to-gas ratios.
It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.
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WO2015/127410 | 8/27/2015 | WO | A |
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