Wave transmission lines and networks – Coupling networks – Frequency domain filters utilizing only lumped parameters
Reexamination Certificate
2002-05-14
2004-11-02
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Frequency domain filters utilizing only lumped parameters
C333S176000
Reexamination Certificate
active
06812811
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
Not applicable.
FIELD OF THE INVENTION
The present invention relates to control systems and apparatus for selectively supplying electrical power in a remote environment. More particularly, the invention relates to systems and apparatus for remotely filtering power through one or more electrical circuits located downhole in oil and gas wells to selectively power a device proximate the electrical circuit.
BACKGROUND OF THE INVENTION
In the operation of electrically powered equipment, systems and apparatus are sometimes employed to operate the equipment in remote and hostile environments. For example, in the operation of hydrocarbon wells, the production of hydrocarbons to the surface of the well at times requires the assistance of downhole production systems. Generally, after a well is drilled, cased and cemented, a fluid path from the wellbore is established with the zones of reservoirs containing hydrocarbons. One or more production tubing strings are traditionally installed in the cased wellbore to accommodate the flow of hydrocarbons to the surface. While hydrocarbons from some reservoirs flow through the production tubing to the surface relatively unassisted, other reservoirs require the assistance of production systems which are installed downhole. Such production equipment is traditionally coupled to the tubing string.
One type of production system is a gas lift operation that includes a valve system for controlling the injection of relatively high pressure gas from the surface into the wellbore. The pressurized gas is injected into the annular space between the casing and tubing and enters the tubing through downhole gas lift valves. The gas lifts the fluids that are collecting in the tubing to assist the flow of hydrocarbon fluids to the surface. Gas injection into the well thus requires the operation of the downhole gas lift valve to control the injection gas flow. The gas lift valves are strategically positioned along the production tubing string in relatively close proximity to the hydrocarbon laden zones. The valves are normally closed to restrict the flow of injection gas from the casing into the tubing and are opened to allow the flow of injection gas into the tubing. Generally, gas lift valves are hydraulically operated. By controlling the flow of a hydraulic fluid, a downhole hydraulic valve is actuated to control the flow of fluid into the gas lift valve. The gas lift valve is moved from a closed to an open position for as long as necessary to affect the flow of the pressurized gas from the casing into the tubing. Such gas lift valves are position instable. Upon interruption of the hydraulic control pressure, the gas lift valve returns to its normally closed configuration.
In a gas lift system, there is a requirement for the periodic operation of a motor valve at the surface of the well to control either the flow of fluids from the well or the flow of injection gas into the well to assist in the hydrocarbon production. These motor valves are controlled by timing mechanisms and are set at predetermined time periods so that a well is either restricted from the flow of gas or liquids to the surface or is allowed to freely produce.
It will be appreciated that timed intermittent operation of motor valves and similar devices located at the surface of a well is often not adequate to control either outflow from the well or gas injection to the well so as to optimize well production. Computerized controllers have thus been developed for controlling downhole production equipment. In general, there are control systems that use a surface microprocessor and downhole control systems which are initiated by surface control signals. The control electronics of these computerized systems are located at the surface of a well and communicate with sensors and electromechanical devices near the surface. For example, some systems include fully programmable microprocessor controllers which monitor downhole parameters such as pressure and flow and control the operation of gas injection to the well, outflow of fluids from the well or shutting in of the well. These systems may include battery powered solid state circuitry comprising a keyboard, a programmable memory, a microprocessor, control circuitry and a liquid crystal display. Other systems use a controller having serial and parallel communication ports through which all communications to and from the controller pass. Hand held devices or portable computers capable of serial communication may access the controller. A telephone modem or telemetry link to a central host computer may also be used to permit several controllers to be accessed remotely.
Downhole control systems generally include downhole microprocessor controllers, electromechanical control devices and sensors. For example, some downhole microprocessor controllers transmit control signals upon actuation from a surface or other external control signal. Other production well control systems comprise downhole sensors, downhole electromechanical devices and downhole computerized control electronics wherein the control electronics automatically control the electromechanical devices based on input from the downhole sensors. The downhole computerized control system will monitor actual downhole parameters such as pressure, temperature, flow and gas influx, all sensed by the downhole sensors, and automatically execute control instructions when the monitored downhole parameters are outside a selected operating range. The automatic control instructions will then cause an electromechanical control device such as a valve to actuate the appropriate tool. The selected operating range for each tool controlled by the downhole control system is programmed in a downhole memory either before or after the control system is lowered downhole. A transceiver may be used to change the operating range or alter the programming of the control system from the surface of the well or from a remote location. A power source provides energy to the downhole control system. Power for the power source can be generated in the borehole, at the surface or via energy storage devices such as batteries, or a combination thereof. The power source provides electrical voltage and current to the downhole electronics, electromechanical devices and sensors in the borehole.
While it is recognized that hydrocarbon production wells will have increased production efficiencies and lower operating costs if surface computer based controllers and downhole microprocessor controllers are used, the implemented control systems of the prior art nevertheless have certain drawbacks. In particular, the controllers of such systems include complex circuitry that is sensitive to environment conditions such as pressure and temperature. The downhole circuitry would thus require containment in canisters capable of withstanding hostile conditions that are present in downhole environments. In addition, the substantial numbers of components which comprise the microprocessors create reliability, repair and maintenance issues which are relatively expensive to address, as the downhole circuitry would have to be removed from the well in order to be repaired or replaced.
While the control system and apparatus of the present invention are discussed in the context of a downhole environment, it will be appreciated that the present invention is also application to other systems which require operation in remote and hostile conditions.
SUMMARY OF THE INVENTION
Through significant time and effort, it has been found that the difficulties associated with microprocessors could be avoided by the control system of the present invention that uses relatively simple electrical circuitry. As will be appreciated by one skilled in the art, the novel apparatus and control system of the present invention are applicable to other types of equipment other than downhole equipment for which remote operatio
Goiffon John J.
Pool Charles M.
Robison Clark E.
Skinner Neal G.
Halliburton Energy Service,s Inc.
Pascal Robert
Piper Michael W.
Takaoka Dean
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