Method and apparatus for controlling the data rate of a downhole acoustic transmitter in a logging-while-drilling system

Claim 3

The method of claim 1 wherein the setting of the data rate comprises: a. generating a clock signal, b. dividing said clock signal in response to said control signal, thereby producing timing pulses with time periods representative of said control signal, and c. utilizing said timing pulses to set the number of acoustic periods for transmitting each data bit of information.

Claim 4

The method of claim 2 wherein said step of dividing said clock signal in response to said control signal comprises: a. producing a time integral of said control signal, b. comparing said time integral with a plurality of reference signals and producing comparison signals corresponding with each of said reference signals, each comparison signal being of a first state when said time integral is less than said reference signal and of a second state when said time integral exceeds said reference signal, c. selectively combining comparison signals to provide a coded word which represents the data rate setting, and d. utilizing said coded word to control the division of said clock signal into said timing pulses.

Claim 5

The method of claim 3 wherein the data rate setting may be changed by: a. varying from the surface of the earth an additional operating parameter of the logging-while-drilling system, and b. changing the state of at least one of said plurality of comparison signals in response to the change in said additional operating parameter, thereby changing the coded word representing the data rate setting.

Claim 6

A logging-while-drilling system for controlling from the surface of the earth the rate at which data derived from measured downhole conditions is transmitted from a downhole acoustic transmitter to the surface of the earth, comprising: a. means for varying from the surface of the earth the operating parameters of the logging-while-drilling system, b. means, located downhole, for detecting variations in said operating parameters and producing a first control signal for the period of time at least one of said operating parameters is within a predetermined range, and c. means responsive to said first control signal for providing timing pulses which set the data rate of the downhole acoustic transmitter, the timing pulses being representative of the period of said control signal, whereby the data rate setting is controlled from the surface of the earth by controlling the period of time said operating parameter is within a predetermined range.

Claim 7

A logging-while-drilling system for controlling from the surface of the earth the rate at which data derived from measured downhole conditions is transmitted from a downhole acoustic transmitter to the surface of the earth, comprising: a. means for varying from the surface of the earth the operating parameters of the logging-while-drilling system, b. means, located downhole, for detecting variations in said operating parameters and producing a first control signal for the period of time at least one of said operating parameters is within a predetermined range, and c. means responsive to said first control signal for providing timing pulses which set the data rate of the downhole acoustic transmitter, the timing pulses being representative of the period of said control signal, whereby the data rate setting is controlled from the surface of the earth by controlling the period of time said operating parameter is within a predetermined range.

Claim 8

The system of claim 5 wherein said means for providing timing pulses comprises: a. means for providing a time integral of said first control signal, b. a plurality of comparators for comparing said time integral with a plurality of reference signals, the output of said comparators being a plurality of comparison signals of a first state when said time integral is less than the reference signal to which it is compared and of a second state when said time integral exceeds the reference signal to which it is compared, c. means responsive to said comparison signals for producing a coded word defining the data rate setting of the acoustic transmitter, d. a source of clock pulses, and e. a programmable frequency divider which is programmed by said coded word to divide said clock pulses into the timing pulses required to set the data rate of the acoustic transmitter.

Claim 9

The system of claim 6 further including: a. means for producing a second control signal upon the variation of at least a second of said operating parameters, and b. means responsive to said second control signal for changing the binary state of at least one of said binary bits, whereby said programmable frequency divider is reprogrammed to produce the timing pulses required for a new data rate setting of the acoustic transmitter.

Claim 10

In a logging-while-drilling system employing a drill bit connected to a rotary drill string through which a drilling fluid is circulated by means of a surface pump, a plurality of transducers for measuring downhole conditions, and an acoustic transmitter for telemetering the information from the downhole location to the surface of the earth, the combination comprising: a. a surface-to-downhole communication channel, b. means located downhole in said communication channel for producing a first signal indicative of the condition of said communication channel, c. means located on the earth''s surface for changing the condition in said communication channel, d. means located downhole for producing a pair of reference signals, said reference signals defining a predetermined range in the condition of said communication channel, e. means for comparing said first signal with the pair of reference signals for the communication channel and for providing a control signal during the period of time said first signal is within the predetermined range defined by said pair of reference signals, f. an integrator for providing a time integral of said control signal, g. means for providing a plurality of second reference signals, h. means for providing a plurality of comparison signals corresponding with said plurality of second reference signals, said comparison signals being of a first state when said time integral is less than the corresponding reference signal, and being of a second state when said time integral exceeds the corresponding reference signal, i. means responsive to said comparison signals for producing a plurality of complement signals, said complement signals being of the opposite state from the corresponding comparison signals, j. a source of clock pulses, k. a programmable frequency Divider which divides said clock pulses into timing pulses, said divider being programmed by a selective combination of said comparison signals and said complement signals, whereby the frequency of said timing pulses is set from the surface of the earth by controlling the length of time that the condition within said communication channel is within the predetermined limits defined by said first reference signals, and l. means for applying said timing pulses to said acoustic transmitter, the frequency of said timing pulses defining the rate at which the acoustic transmitter transfers data derived from measured downhole conditions to the surface of the earth.

Claim 11

In a logging-while-drilling system employing a drill bit connected to a rotary drill string through which a drilling fluid is circulated by means of a surface pump, a plurality of transducers for measuring downhole conditions, and an acoustic transmitter for telemetering the information from the downhole location to the surface of the earth, the combination comprising: a. a surface-to-downhole communication channel, b. means located downhole in said communication channel for producing a first signal indicative of the condition of said communication channel, c. means located on the earth''s surface for changing the condition in said communication channel, d. means located downhole for producing a pair of reference signals, said reference signals defining a predetermined range in the condition of said communication channel, e. means for comparing said first signal with the pair of reference signals for the communication channel and for providing a control signal during the period of time said first signal is within the predetermined range defined by said pair of reference signals, f. an integrator for providing a time integral of said control signal, g. means for providing a plurality of second reference signals, h. means for providing a plurality of comparison signals corresponding with said plurality of second reference signals, said comparison signals being of a first state when said time integral is less than the corresponding reference signal, and being of a second state when said time integral exceeds the corresponding reference signal, i. means responsive to said comparison signals for producing a plurality of complement signals, said complement signals being of the opposite state from the corresponding comparison signals, j. a source of clock pulses, k. a programmable frequency Divider which divides said clock pulses into timing pulses, said divider being programmed by a selective combination of said comparison signals and said complement signals, whereby the frequency of said timing pulses is set from the surface of the earth by controlling the length of time that the condition within said communication channel is within the predetermined limits defined by said first reference signals, and l. means for applying said timing pulses to said acoustic transmitter, the frequency of said timing pulses defining the rate at which the acoustic transmitter transfers data derived from measured downhole conditions to the surface of the earth.

Claim 12

The system of claim 8 further including: a. at least a second surface-to-downhole communication channel, b. means located on the surface of the earth for changing the condition in said second communication channel, c. means located downhole and responsive to the condition in said second communication channel for producing a second control signal upon a change in said condition, and d. means responsive to said second control signal for changing the state of at least one of said comparison signals and said complement signals, whereby the frequency of said timing pulses, which frequency defines the data rate of said acoustic transmitter, may be changed from the surface of the earth by changing the condition in said second communication channel.