Method and apparatus for use in investigating earth formations

Claim 2

In a well logging system, apparatus for detecting a periodically occurring pulse transmitted from a remote location on the same transmission channel and frequency band with a pluralitY of other pulses and wherein said periodic pulse is always preceded by a dead period defined by an absence of transmitted pulses in said frequency band, comprising: means for receiving the transmitted pulses and passing all pulses on the frequency band of said periodic pulses; retriggerable pulse generating means responsive to at least a portion of said passed pulses for generating a first control signal having a first given time duration, said retriggerable means adapted to restart its timing cycle in response to each triggering pulse and said first given time duration being less than said dead period; detecting means responsive to an enabling signal for detecting a selected passed pulse as one of said periodic pulses; and enabling means responsive to each detected periodic pulse and said first control signal for producing said enabling signal to enable said detecting means during a time interval when one of said periodic pulses is expected.

Claim 3

The apparatus of claim 1 wherein said enabling means includes timing means responsive to each detected periodic pulse for producing a second control signal which terminates a second given time interval after said timing means is energized by one of said detected periodic pulses, said second given time interval being less than the time interval between successive ones of said periodic pulses; and means responsive to said first and second control signals for enabling said detecting means to detect a passed pulse as one of said periodic pulses.

Claim 4

In a well logging system, apparatus for detecting a periodically occurring pulse transmitted from a remote location on the same transmission channel and frequency band with a plurality of other pulses and wherein said periodic pulse is always preceded by a dead period defined by an absence of transmitted pulses in said frequency band, comprising: means for receiving the transmitted pulses and passing all pulses on the frequency band of said periodic pulses; detecting means responsive to an enabling signal for detecting a selected passed pulse as one of said periodic pulses; timing means responsive to each detected periodic pulse for producing a first control signal which terminates a first given time interval after said timing means is energized by one of said detected periodic pulses, said first given time interval being less than the time interval between successive ones of said periodic pulses; retriggerable pulse generating means responsive to at least a portion of said passed pulses and the trailing edge of each first control signal for generating a second control signal having a second given time duration, said retriggerable means adapted to restart its timing cycle in response to each triggering pulse and said second given time duration being less than said dead period; and enabling means responsive to said first and second control signals for generating said enabling signal to enable said detecting means to detect a passed pulse as one of said periodic pulses.

Claim 5

In a well logging system, apparatus for detecting a periodically occurring pulse transmitted from a remote location on the same transmission channel and frequency band with a plurality of other pulses and wherein said periodic pulse is always preceded by a dead period defined by an absence of transmitted pulses in said frequency band, comprising: means for receiving the transmitted pulses and passing all pulses on the frequency band of said periodic pulses; detecting means responsive to an enabling signal for detecting a selected passed pulse as one of said periodic pulses; timing means responsive to each detected periodic pulse for producing a first control signal which terminates a first given time interval after said timing means is energized by one of said detected periodic pulses, said first given time interval being less than the time interval between successive ones of said periodic pulses; retriggerable pulse generating means responsive to at least a portion of said passed pulses and the trailing edge of each first control signal for generating a second control signal having a second given time duration, said retriggerable means adapted to restart its timing cycle in response to each triggering pulse and said second given time duration being less than said dead period; and enabling means responsive to said first and second control signals for generating said enabling signal to enable said detecting means to detect a passed pulse as one of said periodic pulses.

Claim 6

The apparatus of claim 3 wherein said enabling means includes means responsive to the absence of both of said first and second control signals for producing said enabling signal, and to the presence of either one of said control signal for inhibiting the generation of said control signal whereby a detected periodic pulse energizing said timing means will cause said detecting means to be enabled during a dead time period just prior to the arrival at the surface of the earth of the next one of said periodic pulses.

Claim 7

The apparatus of claim 4 wherein said enabling means further includes means responsive to each detected periodic pulse for inhibiting the generation of said enabling signal so that another pulse will not be detected as one of said periodic pulses until the next periodic pulse is expected.

Claim 8

In a well logging system of the type where energy is repetitively emitted from a transmitter and received by at least two nearby receivers which individually pRoduce signals representative of the received energy for transmission to the surface of the earth on selected occurrences of energy emission, and wherein a sync pulse representative of the time of energy emission is also transmitted to the surface of the earth, apparatus for identifying the received energy signals at the surface of the earth, comprising: means for detecting each sync pulse; means for detecting each received energy signal; means for measuring the time interval between each detected sync pulse and a subsequent detected received energy signal and generating time interval pulses representative thereof; and identifying means responsive to said time interval signals for identifying which receiver produced each received energy signal.

Claim 9

In a well logging system of the type where energy is repetitively emitted from a transmitter and received by at least two nearby receivers which individually pRoduce signals representative of the received energy for transmission to the surface of the earth on selected occurrences of energy emission, and wherein a sync pulse representative of the time of energy emission is also transmitted to the surface of the earth, apparatus for identifying the received energy signals at the surface of the earth, comprising: means for detecting each sync pulse; means for detecting each received energy signal; means for measuring the time interval between each detected sync pulse and a subsequent detected received energy signal and generating time interval pulses representative thereof; and identifying means responsive to said time interval signals for identifying which receiver produced each received energy signal.

Claim 10

The apparatus of claim 6 wherein said identifying means includes means for comparing the time interval pulses with one another and identifying said received energy signals in accordance with the relationship of the time interval pulses to one another.

Claim 11

In a well logging system of the type where energy is repetitively emitted from a transmitter and received by at least two nearby receivers which individually produce signals representative of the received energy for transmission to the surface of the earth on selected occurrences of energy emission, ans wherein a sync pulse representative of the time of energy emission is also transmitted to the surface of the earth, apparatus for identifying the received energy signals at the surface of the earth, comprising; means for detecting each sync pulse; means responsive to a selected portion of each received energy signal for generating a received energy timing pulse; means for measuring the time interval between each detected sync pulse and a subsequent received energy timing pulse and generating time interval pulses representative thereof; accumulating means responsive to said time interval pulses for adding or subtracting a function representative of each measured time interval to produce an accumulation signals; identifying means responsive to said detected sync pulses and adapted for producing signals representative of which receiver produced each received energy signal for application to said accumulating means to control whether said accumulating means adds or subtracts each of said functions; and means responsive to a selected condition of said accumulation signal for resetting said identifying means to a proper state whenever said identifying means inaccurately identifies said received energy signals.

Claim 12

In a well logging system of the type where energy is repetitively emitted from a transmitter and received by at least two nearby receivers which individually produce signals representative of the received energy for transmission to the surface of the earth on selected occurrences of energy emission, ans wherein a sync pulse representative of the time of energy emission is also transmitted to the surface of the earth, apparatus for identifying the received energy signals at the surface of the earth, comprising; means for detecting each sync pulse; means responsive to a selected portion of each received energy signal for generating a received energy timing pulse; means for measuring the time interval between each detected sync pulse and a subsequent received energy timing pulse and generating time interval pulses representative thereof; accumulating means responsive to said time interval pulses for adding or subtracting a function representative of each measured time interval to produce an accumulation signals; identifying means responsive to said detected sync pulses and adapted for producing signals representative of which receiver produced each received energy signal for application to said accumulating means to control whether said accumulating means adds or subtracts each of said functions; and means responsive to a selected condition of said accumulation signal for resetting said identifying means to a proper state whenever said identifying means inaccurately identifies said received energy signals.

Claim 13

A well logging system, comprising: a well tool having an energy emitting transmitter and at least two nearby energy receiving receivers; means for repetitively energizing said transmitter to emit energy into a media surrounding said well tool and producing a sync pulse representative of the time of energy emission for transmission to the surface of the earth; means coupled to said receivers and operable in synchronism with each energy emission for transmitting the signals developed by each receiver to the surface of the earth on selected emission of energy; means at the surface of the earth for detecting each transmitted sync pulse and receiver signal; means for measuring the time interval between each detected sync pulse and a subsequent detected received energy signal and generating a time interval pulse representative thereof; and identifying means responsive to a relationship of said time interval pulses to one another for identifying which receivers produced each receiver signal.

Claim 14

A well logging system, comprising: a well tool having an energy emitting transmitter and at least two nearby energy receiving receivers; means for repetitively energizing said transmitter to emit energy into a media surrounding said well tool and producing a sync pulse representative of the time of energy emission for transmission to the surface of the earth; means coupled to said receivers and operable in synchronism with each energy emission for transmitting the signals developed by each receiver to the surface of the earth on selected emission of energy; means at the surface of the earth for detecting each transmitted sync pulse and receiver signal; means for measuring the time interval between each detected sync pulse and a subsequent detected received energy signal and generating a time interval pulse representative thereof; and identifying means responsive to a relationship of said time interval pulses to one another for identifying which receivers produced each receiver signal.

Claim 15

The apparatus of claim 9 wherein said identifying means includes accumulating means responsive to said time interval pulses for adding or subtracting a function representative of each measured time interval to produce an accumulation signal, means responsive to said detected sync pulses and a selected condition of said accumulation signal for identifying each receiver signal.

Claim 16

A well lOgging system, comprising: a well tool having an energy emitting transmitter and two nearby energy receiving receivers; means for repetitively energizing said transmitter to emit energy into a media surrounding said well tool and producing a sync pulse representative of the time of energy emission for transmission to the surface of the earth; means coupled to said receivers and operable in synchronism with each energy emission for transmitting the signals developed by each receiver to the surface of the earth on alternate emissions of energy; means at the surface of the earth for detecting each transmitted sync pulse and receiver signal; means for measuring the time interval between each detected sync pulse and a subsequent detected received energy signal and generating a time interval pulse representative thereof; and identifying means responsive to the relative time period of said time interval pulses to one another for identifying which receiver produced each receiver signal whereby the time period of the time interval pulse corresponding to the nearest receiver to said transmitter will be less than that corresponding to the farthest receiver therefrom to thereby enable said receiver signals to be identified.

Claim 17

A well lOgging system, comprising: a well tool having an energy emitting transmitter and two nearby energy receiving receivers; means for repetitively energizing said transmitter to emit energy into a media surrounding said well tool and producing a sync pulse representative of the time of energy emission for transmission to the surface of the earth; means coupled to said receivers and operable in synchronism with each energy emission for transmitting the signals developed by each receiver to the surface of the earth on alternate emissions of energy; means at the surface of the earth for detecting each transmitted sync pulse and receiver signal; means for measuring the time interval between each detected sync pulse and a subsequent detected received energy signal and generating a time interval pulse representative thereof; and identifying means responsive to the relative time period of said time interval pulses to one another for identifying which receiver produced each receiver signal whereby the time period of the time interval pulse corresponding to the nearest receiver to said transmitter will be less than that corresponding to the farthest receiver therefrom to thereby enable said receiver signals to be identified.

Claim 18

The apparatus of claim 11 wherein said identifying means includes means responsive to said detected sync pulses for generating identification signals representative of which receiver produced each receiver signal; accumulating means responsive to said time interval pulses and said identification signals for adding a function related to a time interval pulse which corresponds to the receiver signal from one of the receivers and subtracting a function related to a time interval pulse which corresponds to the receiver signal from the other of said receivers; and means responsive to a given state of said accumulating means for controlling said identification signal generating means to properly identify the receiver signals.

Claim 19

A well logging system, comprising: a well tool having first and second exploring means, said first exploring means adapted to produce first pulses representative of a measured parameter for transmission to the surface of the earth, and said second exploring means having an energy emitting transmitter and at least two nearby energy receiving receivers, means for periodically energizing said transmitter to emit energy into a media surrounding the well tool and producing a sync pulse representative of the time of energy emission for transmission to the surface of the earth, means coupled to said receivers for transmitting receiver signals representative of the energy received by each receiver on selected emissions of energy, and means operable in synchronism with each energy emission for inhibiting the transmission of said first pulses from a selected time prior to the transmission of a sync pulse until a selected time subsequent to the transmission of a following receiver signal; retriggerable pulse generating means at the surface of the earth responsive to at least a portion of said pulses for generating a first control signal having a first given time duration, said retriggerable means adapted to restart its timing cycle in response to each triggering pulse, said first given time duration being less than the transmission dead period during the time interval between the transmission of one of said first pulses and said sync pulse; detecting means responsive to an enabling signal for detecting a selected one of said transmitted pulses at the surface of the earth as a sync pulse; timing means responsive to said detected sync pulse for producing a second control signal which terminates a second given time interval after said timing means is energized by one of said detected sync pulses, said second given time interval being less than the time interval between successives ones of said sync pulses; and means responsive to said first and second control signals for enabling said deTecting means to detect a pulse as one of said sync pulses.

Claim 20

A well logging system, comprising: a well tool having first and second exploring means, said first exploring means adapted to produce first pulses representative of a measured parameter for transmission to the surface of the earth, and said second exploring means having an energy emitting transmitter and at least two nearby energy receiving receivers, means for periodically energizing said transmitter to emit energy into a media surrounding the well tool and producing a sync pulse representative of the time of energy emission for transmission to the surface of the earth, means coupled to said receivers for transmitting receiver signals representative of the energy received by each receiver on selected emissions of energy, and means operable in synchronism with each energy emission for inhibiting the transmission of said first pulses from a selected time prior to the transmission of a sync pulse until a selected time subsequent to the transmission of a following receiver signal; retriggerable pulse generating means at the surface of the earth responsive to at least a portion of said pulses for generating a first control signal having a first given time duration, said retriggerable means adapted to restart its timing cycle in response to each triggering pulse, said first given time duration being less than the transmission dead period during the time interval between the transmission of one of said first pulses and said sync pulse; detecting means responsive to an enabling signal for detecting a selected one of said transmitted pulses at the surface of the earth as a sync pulse; timing means responsive to said detected sync pulse for producing a second control signal which terminates a second given time interval after said timing means is energized by one of said detected sync pulses, said second given time interval being less than the time interval between successives ones of said sync pulses; and means responsive to said first and second control signals for enabling said deTecting means to detect a pulse as one of said sync pulses.

Claim 21

The apparatus of claim 13 and further including means responsive to a given portion of each receiver signal for producing a receiver signal timing pulse, means for measuring the time interval between each detected sync pulse and a subsequent receiver signal timing pulse and generating time interval pulses representative thereof; and means responsive to said time interval pulses for identifying which receiver produced each receiver signal.

Claim 26

A well logging method, comprising: moving a well tool having an energy emitting transmitter and at least two nearby energy receiving receivers through a borehole; repetitively energizing said transmitter to emit energy into a media surrounding said well tool and producing a sync pulse representative of the time of energy emission for transmission to the surface of the earth; transmitting signals developed by each receiver in response to the emitted energy to the surface of the earth on selected, non-successive emissions of energy; detecting each transmitted sync pulse and receiver signal at the surface of the earth; measuring the time interval between each detected sync pulse and a subsequent detected received energy signal; and identifying which receiver produced each receiver signal in response to the relationship of said measured time intervals to one another.

Claim 27

A well logging method, comprising: moving a well tool having an energy emitting transmitter and at least two nearby energy receiving receivers through a borehole; repetitively energizing said transmitter to emit energy into a media surrounding said well tool and producing a sync pulse representative of the time of energy emission for transmission to the surface of the earth; transmitting signals developed by each receiver in response to the emitted energy to the surface of the earth on selected, non-successive emissions of energy; detecting each transmitted sync pulse and receiver signal at the surface of the earth; measuring the time interval between each detected sync pulse and a subsequent detected received energy signal; and identifying which receiver produced each receiver signal in response to the relationship of said measured time intervals to one another.

Claim 28

The method of claim 17 wherein the stop of identifying the receiver signals includes adding or subtracting a function representative of each measured time interval to produce an accumulation signal, monitoring the condition of said accumulation signal to identify each receiver signal.

Claim 29

A well logging method, comprising: moving a well tool having an energy emitting transmitter and two nearby energy receiving receivers through a borehole; repetitively energizing said transmitter to emit energy into a media surrounding said well tool and producing a sync pulse representative of the time of energy emission foR transmission to the surface of the earth; transmitting signals developed by each receiver in response to the emitted energy to the surface of the earth on alternate emissions of energy; detecting each transmitted sync pulse and receiver signal at the surface of the earth; measuring the time interval between each detected sync pulse and a subsequent detected received energy signal; and monitoring the time period relationship of said measure time intervals to one another to identify which receiver produced each receiver signal whereby the time period of the measured time interval corresponding to the nearest receiver to said transmitter will be less than that corresponding to the farthest receiver therefrom to thereby enable said receiver signals to be identified.

Claim 30

A well logging method, comprising: moving a well tool having an energy emitting transmitter and two nearby energy receiving receivers through a borehole; repetitively energizing said transmitter to emit energy into a media surrounding said well tool and producing a sync pulse representative of the time of energy emission foR transmission to the surface of the earth; transmitting signals developed by each receiver in response to the emitted energy to the surface of the earth on alternate emissions of energy; detecting each transmitted sync pulse and receiver signal at the surface of the earth; measuring the time interval between each detected sync pulse and a subsequent detected received energy signal; and monitoring the time period relationship of said measure time intervals to one another to identify which receiver produced each receiver signal whereby the time period of the measured time interval corresponding to the nearest receiver to said transmitter will be less than that corresponding to the farthest receiver therefrom to thereby enable said receiver signals to be identified.

Claim 31

The method of claim 19 wherein the step of monitoring includes generating identification signals representative of which receiver produced each receiver signal in response to said detected sync pulses, adding a function related to a time interval pulse which corresponds to the receiver signal from one of the receivers and subtracting a function related to a time interval pulse which corresponds to the receiver signal from the other of said receivers in response to said identification signals to produce an accumulation signal, monitoring the state of said accumulation signal and controlling the generation of said identification signals in response to said accumulation signal state so that said identification signals will properly identify the receiver signals.