Wells – Processes – Heating – cooling or insulating
Reexamination Certificate
1999-12-01
2001-11-20
Bagnell, David (Department: 3672)
Wells
Processes
Heating, cooling or insulating
C166S060000, C166S062000
Reexamination Certificate
active
06318467
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a system and method for pumping and heating viscous fluids to be produced from petroleum production wells and the like. More particularly, the invention relates to a system and method for heating fluids in the vicinity of a submergible pumping system of the type employed to produce fluids from petroleum wells.
BACKGROUND OF THE INVENTION
In the field of petroleum production, various techniques may be employed for raising viscous fluids, such as crude oil to the earth's surface from a wellbore. In a typical well, perforations are formed in the casing of a wellbore through which production fluids, such as crude oil, may penetrate and collect in the wellbore. Where ambient pressures are insufficient to force the fluid to the earth's surface for processing, submergible pumps are typically employed to pump production fluids up through the wellbore to collection points. Such wells and pumping arrangements may be located both on dry land and beneath bodies of water, such as over continental shelves, lakes, swamps and the like.
Known submergible pumping systems for petroleum wells typically include a pump coupled to a submergible electric motor. A motor protector may be provided adjacent to the electric motor to protect against temperature and pressure variations in the portion of the wellbore where the submergible unit will be positioned. Inlet apertures surrounding the pump allow production fluids to flow into the pump. The electric motor drives the pump in rotation to pressurize the production fluids and to force them through a conduit to the earth's surface. Pumping units generally of this type are commercially available from Reda of Bartlesville, Okla.
While heretofore known pumping systems are generally sufficient to collect and pump many production fluids from wellbores, they may experience difficulties in handling particularly viscous or heavy fluids. Because the viscosity of such fluids is generally a function of temperature, in certain applications heaters have been employed adjacent to submergible pumping units to preheat the fluids until their viscosity becomes sufficiently low to be pumped from the wellbore. In extreme cases, such heaters may be employed to melt solidified petroleum, paraffin waxes, hydrates and the like which can, once liquefied, be pumped via the submergible pumping system to the earth's surface.
Submergible heating systems of the type mentioned above are commonly attached to existing pumping systems including electric motor and pump sets. The heating system is powered by electrical energy transmitted through independent cables which run adjacent to the pumping system and upward through the wellbore to a power supply located at the earth's surface. Control of the heating unit is accomplished by modulating power input to the heating unit through the power supply cables. Because the heating unit is powered independently of the pumping unit, the heating unit cables are in addition to the power supply and control cables used to provide electrical energy for driving the electric motor.
While such arrangements may, in certain applications, provide adequate heating for viscous wellbore fluids, they are not without drawbacks. For example, depending upon the relative sizes of the wellbore casing and of the electric motor and pump assembly, very little clearance may be available in the wellbore for the additional power cables necessary to supply electrical energy to the heater. Similarly, the provision of multiple power cables for the heating unit and the pumping unit add considerable cost and weight to the pumping system. Furthermore, such arrangements typically require separate power supplies and associated controls for the heating unit and the submergible electric motor. All of these factors contribute to significantly increasing the overall cost of the submergible pumping system and render the equipment more difficult to assemble, install and manage.
There is a need, therefore, for an improved technique for heating viscous fluids in a well which addresses these drawbacks of existing systems. In particular, there is a need for a submergible pumping system which can, in addition to pumping, reduce the viscosity of the viscous fluids adjacent to the pumping unit by heating these viscous fluids and thereby improve the ability of the submergible pumping system to pump and which does not require the addition of heater elements to the submergible pumping system.
SUMMARY OF THE INVENTION
The invention provides a system and method for pumping and heating viscous fluids adjacent to a submergible pumping unit that is designed to respond to these existing needs. The system and method may be used in a variety of applications, but is particularly well suited to heating production fluids, such as crude oil in petroleum wells and the like. The system employs a submergible pumping unit that includes a submergible electric motor drivingly coupled to a submergible pump. The system further includes at least one electric power supply to provide power to operate the submergible pumping unit to pump viscous fluids and to generate heat. The submergible electric motor has a plurality of phases and each phase is transmitted power by a plurality of electrical conductors. Electric power is provided through the electrical conductors to the submergible electric motor by a switchboard. When pumping viscous fluids in a wellbore the submergible pumping system can generate heat in the pumping system itself and in the power cable to heat the viscous fluids. When not pumping viscous fluids the system can generate heat due to current flowing in the power cable conductors and the submergible electric motor by supplying electric power and maintaining the submergible electric motor in a stationary-rotor condition.
According to another aspect of the invention, a system is provided for pumping and heating viscous fluids in a wellbore. The system is comprised of a submergible pumping unit including a multi-phase submergible electric motor drivingly coupled to a submergible pump, a first and a second electrical power supply disposed proximate a surface of the earth to provide power to the submergible pumping unit, a plurality of electrical conductors wherein each phase of the multi-phase submergible electric motor is coupled to a first electrical conductor and a second electrical conductor, and a switchboard coupling the electrical power supplies to the plurality of electrical conductors. In a first switch configuration, the first power supply is coupled through the first and the second electrical conductors of each phase to the multi-phase submergible electric motor and in a second switch configuration the second power supply is coupled through the second electrical conductor to each phase of the multi-phase submergible electric motor.
According to another aspect of the invention, a method is provided for pumping and heating viscous fluids in a wellbore. The method is comprised of the steps of: submerging a submergible pumping unit into the viscous fluid, the submergible pumping unit comprising a submergible pump and a submergible electric motor drivingly coupled to the submergible pump. The method further includes electrically connecting the submergible electric motor to one or more electric power supplies via a plurality of conductors, and supplying electric power to the submergible pumping unit through the plurality of conductors. Viscous fluids are heated due to the heat generated by electric current flowing through the conductors and through the submergible electric motor without operation of the submergible electric motor. The method also includes selectively changing the current flow to operate the submergible electric motor.
REFERENCES:
patent: 2429940 (1947-10-01), McDaniel
patent: 2556435 (1951-06-01), Moehrl et al.
patent: 2601533 (1952-06-01), Koch
patent: 2615114 (1952-10-01), Colby
patent: 2632836 (1953-03-01), Ackley
patent: 2703621 (1955-03-01), Ford
patent: 2738409 (1956-03-01), Bowman
patent
Bailey Rick
Liu Joseph C.
Bagnell David
Camco International Inc.
Dougherty Jennifer R.
Fletcher Yoder & Van Someren
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