Wireline tool for measuring bottom-hole pressure in pumping wells

Claim 1

A data transmission system for use in transmitting data from a data source located in a well to the surface, said system comprising: a first voltage-controlled oscillator, said first oscillator being located in said well and the data source being coupled to said oscillator to control the frequency of the oscillator; a single-conductor cable, said oscillator being coupled to said cable; a second voltage-controlled oscillator, said second voltage-controlled oscillator being located at the surface; and a frequency-phase detecting circuit located at the surface, both said second oscillator and said cable being coupled to said frequency-phase detector, said frequency-phase detector being disposed to detect the difference in frequency and phase between said first and second oscillators and convert said difference to an analog voltage signal, said analog voltage signal being used to control said second oscillator to match the frequency and phase of said second oscillator with the frequency and phase of said first oscillator.

Claim 4

An apparatus for measuring the downhole pressure of a producing well comprising: a plurality of elongated rigid instrument capsules, said capsules having a diameter less than the smallest annular clearance between the well casing and the production tubing; a plurality of flexible connectors, one of said connectors being secured at opposite ends to adjacent ones of said capsules to form a continuous flexible elongated instrument package; a weight, said weight being attached to one end of the instrument package; a pressure transducer, said pressure transducer being mounted is one of said capsules and supplying an electrical analog signal related to the downhole pressure in said well; a voltage-controlled oscillator, said oscillator being mounted is one of said capsules and coupled to said pressure transducer; a cable, said cable being connected to the other end of said instrument package to raise and lower said instrument package in the well, said oscillator being coupled to said cable; a second voltage-controlled oscillator located at the surface; a phase and frequency comparing circuit, said second oscillator and said cable being coupled to said comparing circuit, said comparing circuit producing a voltage to match the frequency and phase of the second oscillator with the frequency and phase of the downhole oscillator; and means for recording the voltage produced by said comparing circuit.

Claim 5

An apparatus for measuring the downhole pressure of a producing well comprising: a plurality of elongated rigid instrument capsules, said capsules having a diameter less than the smallest annular clearance between the well casing and the production tubing; a plurality of flexible connectors, one of said connectors being secured at opposite ends to adjacent ones of said capsules to form a continuous flexible elongated instrument package; a weight, said weight being attached to one end of the instrument package; a pressure transducer, said pressure transducer being mounted is one of said capsules and supplying an electrical analog signal related to the downhole pressure in said well; a voltage-controlled oscillator, said oscillator being mounted is one of said capsules and coupled to said pressure transducer; a cable, said cable being connected to the other end of said instrument package to raise and lower said instrument package in the well, said oscillator being coupled to said cable; a second voltage-controlled oscillator located at the surface; a phase and frequency comparing circuit, said second oscillator and said cable being coupled to said comparing circuit, said comparing circuit producing a voltage to match the frequency and phase of the second oscillator with the frequency and phase of the downhole oscillator; and means for recording the voltage produced by said comparing circuit.