High Temperature Measurement Method and Apparatus (Patent No: 913406)

Inventor: Scholberg, Andre

Location: France

Comments: N/A

Description: THE EMBODll1ENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of making temperature measurements in a well bore comprising the steps of: placing a temperature sensitive resistive element in the well bore by means of a single conductor cable; supplying a constant current on the single conductor to said resistive element and measuring a first signal representative of the voltage required to supply the constant current; removing the temperature sensitive element from the circuit including said conductor by short circuiting the temperature sensitive element; supplying a constant current to said conductor with said temperature sensitive element short circuited and measuring a second signal representative of the voltage required to supply the constant current; and combining said first and second signals to eliminate the resistance of said conductor thereby obtaining the resistance of said temperature sensitive resistive element.

2. The method of claim 1 wherein the steps are performed repetitively as said temperature sensitive element is moved vertically through the well bore and the resistance of said temperature sensitive element is recorded as a function of borehole depth.

3. The method of claim 1 and further including the steps of: measuring the flow rate of fluids in the well bore; and measuring the location in the well bore of the casing joints therein.

4. The method of claim 3 wherein all of the steps are performed repetitively while moving said temperature sensitive element vertically through the well bore and the resistance of said temperature sensitive element, the flow rate of well fluids and the location of casing joints therein are all recorded as a function of borehole depth.

5. The method of claim I further comprising the steps of placing a calibration resistive element together with said temperature sensitive resistive element in the well bore by means of said single conductor cable; removing the calibration resistive element from the circuit including said conductor when measuring said first and second signals; supplying a constant current to the circuit including said conductor and said calibration resistive element and measuring a third signal representative of the voltage required to supply the constant current; and combining said first and second signals with said third signal to correct for any errors due to faulty insulation of said conductor thereby obtaining the resistance of said temperature sensitive resistive element.

6. The method of claim 5 and further including the steps of: measuring the flow rate of fluids in the well bore; and measuring the location in the well bore of the casing joints therein.

7. The method of claim 6 wherein all of the steps are performed repetitively while moving said temperature sensitive element vertically through the well bore and the resistance of said temperature sensitive element, the flow rate of well fluids and the location of casing joints therein are all recorded as a function of borehole depth.

8. Apparatus for performing temperature measurements in a well bore comprising: a temperature sensitive resistive component adapted to be suspended in a well bore by a single conductor cable; means for supplying a constant current to the circuit comprising said temperature sensitive resistive element; means for short circuiting said temperature sensitive element to remove it from the circuit; means for detecting first and second voltages on said cable conductor with said temperature sensitive resistive element respectively in and out of the circuit as the constant current is supplied to the circuit; and means responsive to said first and second detected voltages for generating a signal representative of the resistance of said temperature sensitive element independently of the resistance of said cable.

9. The apparatus of claim 8 and further including: means for moving said temperature sensitive resistive element vertically through the well bore while repetitively detecting the voltages with said temperature' sensitive resistive element in and out of the circuit; and means for recording as a function of borehole depth said signal representative of the resistance of said temperature sensitive resistive element.

10. The apparatus of claim 8 wherein said means for short circuiting said temperature sensitive element includes a relay including a control coil connected in series relationship with said temperature sensitive element and said means for supplying a constant current includes means for supplying a cyclic square wave current capable of alternately opening and closing said relay.

11. The apparatus of claim 10 wherein said means for generating a signal representative of the resistance of said temperature sensitive element includes two measuring circuits respectively adapted for detecting the voltages when said relay is open and closed and a differential circuit responsive to the outputs of said measuring circuits for generating a signal representative of the resistance of said temperature sensitive component independently of the resistance in said cable.

12. The apparatus of claim 11 wherein said two measuring circuits include input amplifiers in which the gains are in the same ratio as the magnitude of said square wave current.

13. The apparatus of claim 12 wherein said temperature sensitive resistive element comprises a metal wire whose resistance varies linearly as a function of temperature.

14. The apparatus of claim 8 and further comprising: a calibration resistive element included in the circuit comprising said temperature sensitive element and said cable conductor; means for supplying a constant current to the circuit comprising said calibration resistive element, said temperature sensitive element and said cable conductor; means for selectively removing said calibration resistive element from said circuit; means for detecting a third voltage on said cable conductor with said calibration resistive element in said circuit; and means responsive to said third detected voltage and to said means responsive to said first and second detected voltages for generating a signal representative of the resistance of said temperature sensitive element independently of any leakage resistance of said cable conductor.

15. The apparatus of claim 14 and further including: means for moving said elements vertically through the well bore while respectively detecting said voltages with either or both said temperature sensitive element and said calibration resistive element in or out of said circuit; and means for recording as a function of borehole depth said signal representative of the resistance of said temperature sensitive element.

16. The apparatus of claim 14 wherein said means for selectively removing either said temperature sensitive element or said calibration resistive element from said circuit includes plural relays having control coils connected in series with said elements, each of said coils being responsive to different magnitudes of current level for activating their respective relay.

17. The apparatus of claim 16 wherein said means for supplying a constant current includes a transmission circuit capable of generating a cyclic square Wave current having at least three different magnitude levels so as to selectively control the closing of said relays.

18. The apparatus of claim 17 and further including two additional sensors, one for detecting casing joints and one for detecting the rate of fluid flow in the borehole, and two additional control relays each of said relays being capable of placing one of the additional sensors into the circuit according to the level of said square wave current.