Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1998-10-29
2001-07-31
Bagnell, David (Department: 3671)
Electrical generator or motor structure
Dynamoelectric
Rotary
C166S105000
Reexamination Certificate
active
06268672
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to motor protectors for protecting submergible motors, such as those used in raising fluids from petroleum wells, and particularly to a system and method that utilizes a neutralizing agent to neutralize corrosive agents before they can damage the internal components of a submergible motor.
BACKGROUND OF THE INVENTION
A variety of production fluids are pumped from subterranean environments. Different types of submergible pumping systems may be disposed in production fluid deposits at subterranean locations to pump the desired fluids to the surface of the earth.
For example, in producing petroleum and other useful fluids from production wells, it is generally known to provide a submergible pumping system for raising the fluids collected in a well. Production fluids, e.g. petroleum, enter a wellbore drilled adjacent a production formation. Fluids contained in the formation collect in the wellbore and are raised by the submergible pumping system to a collection point at or above the surface of the earth.
A typical submergible pumping system includes several components, such as a submergible electric motor that supplies energy to a submergible pump. The system further may include a variety of additional components, including a connector used to connect the submergible pumping system to a deployment system. Conventional deployment systems include production tubing, cable and coiled tubing. Additionally, power is supplied to the submergible electric motor via a power cable that runs along the deployment system.
Often, the subterranean environment, and specifically the well fluid, contains corrosive compounds that may include CO
2
, H
2
S and brine water. These corrosive agents can be detrimental to components of the submergible pumping system, particularly to internal electric motor components, such as copper windings and bronze bearings.
Submergible electric motors are difficult to protect from corrosive agents because of their design requirements that allow use in the subterranean environment. A typical submergible motor is internally filled with a fluid, such as a dielectric oil, that facilitates cooling and lubrication of the motor during operation. As the motor operates, however, heat is generated, which, in turn, heats the internal motor oil causing expansion of the oil. Conversely, the motor cools and the motor oil contracts when the submergible pumping system is not being used.
Accordingly, this type of submergible motor requires a motor oil expansion system able to accommodate the expanding and contracting motor oil. Also, the internal pressure of the motor must be allowed to equalize or at least substantially equalize with the surrounding pressure found within the wellbore. As a result, it becomes difficult to prevent the ingress of corrosive agents into the motor oil and internal motor components.
Numerous types of motor protectors have been designed and used in isolating submergible motors while permitting expansion and contraction of the internal motor oil. A variety of elastomeric bladders alone or in combination with labyrinth sections have been used as a barrier between the well fluid and the motor fluid. For example, expandable elastomeric bags or bladders have been used in series to prevent mixing of wellbore fluid with motor oil while permitting expansion and contraction of the motor oil.
In this latter design, the motor protector includes a pair of chambers that each have an elastomeric bladder. The first bladder is disposed in a first chamber of the pair of chambers and includes an interior in fluid communication with the motor. This fluid communication permits motor oil to flow from the motor into the elastomeric bladder during expansion and to flow from the elastomeric bladder back to the motor during contraction.
The second chamber also includes an expandable bladder, filled with motor oil, that is in fluid communication with the first chamber but external to the first elastomeric bladder. The second chamber also is vented or open to the wellbore environment. This permits fluid to flow between the second elastomeric bladder and the adjacent chamber as the first elastomeric bladder expands or contracts. Simultaneously, wellbore fluid is allowed to flow in and out of the second chamber, external to the second elastomeric bladder, to permit equalization of pressure as the second bladder expands and contracts.
This type of expansion chamber works well in many environments, but certain of the corrosive agents found in at least some wellbore environments include corrosive gases that permeate the elastomeric bags or bladders. These corrosive agents eventually can work their way into the motor oil within the first elastomeric bladder and ultimately corrode and damage internal components of the electric motor.
It would be advantageous to utilize an expandable bladder system in a motor protector without the threat of corrosive agents migrating to the internal components of the electric motor.
SUMMARY OF THE INVENTION
The present invention features a device for protecting a submergible motor from corrosive agents found in a wellbore environment. The device also accommodates the expansion and contraction of the motor oil disposed within an interior of the submergible motor. The device comprises a housing having a first chamber and a second chamber. A first bladder is disposed in the first chamber and includes an interior region in fluid communication with the interior of the submergible motor. A second bladder is disposed in the second chamber and includes an interior region in fluid communication with the first chamber external to the first bladder. The second chamber is exposed to the pressure of the wellbore environment to permit equalization of pressures. Furthermore, a neutralizer is disposed for movement between the interior region of the second bladder and the first chamber external to the first bladder.
According to another aspect of the present invention, a system is provided for incorporation into a motor protector of the type used in protecting a submergible motor from corrosive agents found in a subterranean environment. The submergible motor has an interior filled with a motor oil that aids in cooling and lubrication of the motor. The system includes a bladder having an interior region. The bladder includes a port that permits fluid flow to and from the interior region. The port is connectable to the submergible motor such that motor oil may flow between the interior region of the bladder and the interior of the submergible motor. Also, a liquid neutralant barrier is disposed between the bladder and the subterranean environment to prevent contamination of the motor oil.
According to a further aspect of the present invention, a method is provided for protecting a submergible motor in a submergible pumping system from corrosive agents. The method also provides for the expansion and contraction of a motor oil disposed in the submergible motor. The preferred method comprises connecting a submergible motor with an expandable bladder to permit flow of motor oil between the submergible motor and the expandable bladder. The method further includes holding a supply of liquid neutralant in a neutralant bladder disposed intermediate the motor oil and potential corrosive agents. Further, the method includes neutralizing the corrosive agents before they are able to contaminate the motor oil.
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Haworth Cameron G.
Straub Peter H. G.
Bagnell David
Camco International Inc.
Fletcher Yoder & Van Someren
Petravick Meredith C.
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