Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
  • H03L1/00—Stabilisation of generator output against variations of physical values, e.g. power supply
  • H03L1/02—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only
  • H03L1/04—Constructional details for maintaining temperature constant
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D23/00—Control of temperature
  • G05D23/19—Control of temperature characterised by the use of electric means
  • G05D23/1906—Control of temperature characterised by the use of electric means using an analogue comparing device
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D23/00—Control of temperature
  • G05D23/19—Control of temperature characterised by the use of electric means
  • G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature

Definitions

• This invention relates generally to the provision of a stabilized timing reference such as is provided by solid state timers, crystal oscillators and the like. More particularly, the present invention is directed to the provision of a stable timing reference in downhole well logging instruments for provision of a stabilized time reference signal for effective instrument operation over a large spectrum of operating temperatures while eliminating typical loss of accuracy due to temperature variations, line loss and skew caused by the resistance and capacitance of the lengthy wireline required for a well logging operation.
• Timing devices i.e., solid state timers, such as crystal oscillators and the like
• Solid state timers such as crystal oscillators and the like
• changing the temperature degrades their stability. It is desirable, therefore, to provide means for maintaining the timing device within a designated, quite narrow temperature range that permits the timing device to operate at maximum efficiency and accuracy.
• the ambient temperature of the downhole well environment varies with depth and well location. Thus, during a downhole well logging operation, the logging instrument will typically encounter a wide variety of ambient temperatures depending upon its location in the well bore. Some of these temperatures may be above or below the stable operating temperature range of crystal oscillators and other timing devices.
• timing device or devices are maintained within a narrow temperature range which is an elevated temperature range above that of the maximum ambient temperature of use while operating in a well logging environment where the ambient temperature varies with depth and well location.
• a system for maintaining a high temperature stabilized time base which comprises a low thermal-conduction oven or isolation enclosure of sufficient dimension to accommodate the time base and control circuitry.
• the low thermal-conduction oven is provided with a heating and/or cooling element capable of maintaining a required mass within a predetermined temperature range.
• the heating/cooling oven is provided with a control circuit having a temperature sensor that is designed to monitor internal oven temperature and regulate the supply of electrical power to the heater or to the cooling element as the case may be.
• a timing device is provided which is specifically designed to have frequency stability at a predetermined elevated temperature range.
• the circuit components of the time base is maintained at the predetermined elevated temperature regardless of well temperature to thus ensure the stability of the time base in the downhole environment. Where excessively hot well conditions are encountered, or if the time base circuitry is stable only at a temperature lower than the ambient temperature of the well the protective enclosure for the circuitry may also be provided with controlled cooling to maintain the temperature of the time base within the range of its stability.
• Fig. 1 is a block diagram schematic illustration of a high temperature stabilized time base for well logging instruments which is constructed in accordance with the features of the present invention.
• Fig. 2 is a sectional view of the heat maintaining oven of the stabilized time base of Fig. 1, showing the temperature generation and control devices together with the time base signal generating device being located within the temperature control oven.
• Fig. 3 is a block diagram electronic schematic representing an alternative embodiment of the present invention, for selectively heating or cooling the electronic circuitry.
• a stabilized time base system shown generally at 10 is provided for incorporation within a downhole well logging instrument, a portion of which is shown at 12.
• the stabilized time base includes a low thermal-conductive oven or isolation enclosure 14 is located within the logging instrument 12 and functions as a thermal isolator which is used to contain heat for the purpose of maintaining the efficiency of electronic circuitry disposed within an internal compartment 16 thereof.
• the low thermal- conductive oven also functions to isolate the heat contained therein to lessen the effects of thermal transience to which the instrument 12 might be subjected.
• the oven structure is also employed as the means of mounting the hardware to a backbone.
• the cavity or compartment 16 of the oven structure is of a dimension and design for effective support of the electronic time base and heat control circuitry.
• the oven structure is composed of a material such as polyether ether ketone having a low thermal conductivity and having a characteristic of acceptable thermal expansion.
• the oven structure is composed of a material that is easily machinable or molded for the complex shapes that may be required within the oven cavity 16.
• an electrically energized heating element 18 having the capability of producing sufficient heat to maintain an internal oven temperature at the lowest required ambient temperature that is expected to be encountered within the well bore.
• the electronic heating element has the capability of being energized from an electric power circuit 23 by electrical energy from a suitable source 25 such as a supply cable, onboard battery, etc.
• a cooling element 20 which is electrically energized and controlled through a control circuit 22.
• the cooling element is utilized where the ambient borehole temperature is above that of the oscillator's stable operating temperature, thus requiring cooling in order to maintain the oven cavity 16 within a predetermined temperature range for stability and efficiency of the timing device.
• the cooling element may employ Peltier- Junction cooling to lower the oscillator's temperature when required to maintain its operational stability.
• a temperature sensor 24 which provides temperature signals via conductor 26 to the control circuit 22.
• the control circuit induces energization of the heating element 18 periodically in order to maintain the temperature of the cavity 16 and its circuit components within a narrow predetermined temperature range, being the temperature range within which the timing signal generator is stable.
• the control circuit 22 is selectively coupled via control conductors 28 and 30 to the cooling element 20 and to the heating element 18.
• the heating and cooling elements are selectively energized by the control circuit 22 to introduce heating or cooling into the cavity 16 to compensate for heat gain or loss and thereby maintain a predetermined typically quite narrow temperature range within the cavity.
• a signal generator circuit 32 which may conveniently take the form of a crystal oscillator circuit having a predetermined timing frequency output signal via output conductor 34 which extends through the oven wall structure.
• the control circuit 22 may conveniently be defined by a circuit board having appropriate electrical components for receiving the temperature signal of the sensor 24 and providing operation and control signals to the heating element 18 or cooling element 20.
• the temperature sensor of the control circuit will typically sense temperature of the time base substrate within a range of about 1° C. The temperature is monitored and feedback signals of the temperature sensor are used to control the heater/cooler circuits, thus maintaining the desired temperature within the oven compartment.
• the power source for the temperature sensor must also be maintained at the elevated temperature of the oven compartment to eliminate circuit temperature induced circuit drift. Temperature fluctuations outside the oven affect the heat loss of the oven.
• the control circuitry must sense this change and compensate accordingly.
• the crystal oscillator is a specially designed part that has integrated temperature stability at the desired elevated temperature. The specific crystal oscillator design is not a part of this invention except to the extent that it and its temperature for effective stability of operation are maintained within an appropriate typically narrow predetermined temperature range and it thus provides a stable timing reference over a large spectrum of operating temperatures ranging from 20° C to 300° C and above, which temperature ranges are common in deep petroleum wells.
• the crystal oscillator or other frequency output generator is thus capable of providing a consistent and stable output signal which maintains its accuracy even though the apparatus is subjected to temperature variations. Since the electronic timing signal is generated at the downhole well logging instrument, it is not subjected to temperature variations, line loss and skew that might otherwise be caused by the resistance and capacitance of the lengthy wireline that is ordinarily required for well logging operations. Even though significant changes in ambient temperature are encountered by the well logging instrument during its traverse of the borehole, or its use at different borehole depths, the crystal oscillator or other frequency output device is capable of maintaining a consistent and accurate timing frequency output signal because it is not adversely influenced by ambient temperature changes.
• the temperature within the internal cavity of the low thermal conductive oven is maintained at a narrow temperature range that is above the maximum temperature that is expected to be encountered by the logging instrument at any depth in the well bore.
• the temperature control system will be also provided with a cooling element capable of cooling the temperature of the oven compartment and its circuit components to the desired narrow temperature range.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Automation & Control Theory (AREA)
• Oscillators With Electromechanical Resonators (AREA)
• Geophysics And Detection Of Objects (AREA)
• Measurement Of Unknown Time Intervals (AREA)
• Control Of Temperature (AREA)

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• 1993
  • 1993-11-11 EP EP94902231A patent/EP0635137A4/fr not_active Withdrawn
  • 1993-11-11 CA CA002127809A patent/CA2127809A1/fr not_active Abandoned
  • 1993-11-11 WO PCT/US1993/010932 patent/WO1994011763A1/fr not_active Application Discontinuation
• 1994
  • 1994-07-08 NO NO942573A patent/NO942573L/no unknown

Patent Citations (2)

Non-Patent Citations (1)

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