A single-wire selective perforation system having firing safeguards

Claim 2

In a single-line selective perforating system having a single firing line for electrically connecting a firing control unit to each of a plurality of shot modules, one at a time in a predetermined sequence, where each module is adapted for connecting the connected control unit to a next module, a method of selecting a module for firing characterized by the step of connecting each module one at a time in the predetermined sequence to the firing line under control of module active time intervals internally generated in the modules, where each module generates its active time interval in response to being connected to the firing line with the next module in the sequence automatically connected to the firing line at the end of the active time for the last connected module if that module was not selected for firing during its active time interval.

Claim 3

The method of claim 1 characterized in that each module receives on the firing line both power and firing signals from said control unit, and comprising the steps of: (a) generating internal to each module in response to receipt of the power signals on the firing line (i) a module active time interval during which the module may be selected for firing by a selection control signal from the control unit, and (ii) an identification pulse for transmission over the firing line to the control unit to indicate that a next module has been connected to the firing line; and (b) automatically connecting the firing line to the next module in the sequence at the end of the module active time for the last connected module if that module was not selected for firing during its active time.

Claim 4

The method of claim 2 characterized in that the step of generating an identification pulse comprises generating during the active time interval for each module an identification pulse which uniquely identifies the modules.

Claim 5

The method of claim 1, 2 or 3 characterized in that the step of connecting each module to the firing line comprises the steps of: (a) applying power to the firing line in the form of voltage and current for powering the modules connected to the firing line; (b) generating a module active time interval in the module last connected to the firing line power; (c) controlling at the end of each module active time interval a pass-through switch to pass the firing line power to the next module in the sequence; and (d) repeating steps (b) and (c) until the module to be selected is generating an active time interval.

Claim 6

The method of claim 2 or 3 charaterized in that each module active time interval includes (a) a first portion during which the module generates and applies the identification pulse onto the firing line, and (b) a second portion during which the module is enabled to receive a selection pulse on the firing line from the control unit to select the module for firing.

Claim 7

The method of claim 2 characterized in that the step of generating the identification pulse includes the step of generating a current increase in the firing line power where the amplitude of the firing line current change lies in a predetermined range.

Claim 8

The method of claim 2 or 6 characterized in that the identification pulse for each module must occur within a predetermined time window measured from the occurrence of the last identification pulse.

Claim 9

The method of claim 1 characterized by the steps of: (a) generating an arming pulse to the active module when that module is to be armed for firing; and (b) connecting the detonation portion of the shot in the selected module to the firing line when the module is armed for firing by the arming pulse whereby a firing pulse on the firing line can detonate the selected shot.

Claim 10

The method of claim 3 or 4 characterized in that the step of generating the identification pulse which uniquely identifies the module includes the step of generating a predetermined number of current pulses on the firing line where the time interval to generate the current pulses represents the identification pulse.

Claim 11

The method of claim 9 characterized by the step of providing each module with a different predetermined time base for generating the identification pulse whereby the time intervals of the identification pulses for the modules are each different.

Claim 12

The method of claim 10 characterized by the step of connecting the shot in the selected module to the firing line when the module is selected for firing whereby a firing pulse on the firing line can detonate the selected shot.

Claim 13

The method of claim 11 characterized by the step of connecting the shot to the firing line includes the steps of: (a) generating a predetermined increase in the firing line current in response to a first arming control pulse, the predetermined increase in current indicating that a single module is responding to the arming control pulses; (b) removing the predetermined current increase in the firing line current in response to a second arming control pulse; and (c) connecting the shot to the firing line in response to a third arming control pulse generated if the predetermined change in firing line current is within acceptable limits.

Claim 16

The method of claim 5 wherein the first and second portions of each active time interval are equal in length.

Claim 18

A single-wire selective perforating system for selectively detonating the charges in a plurality of firing modules, one at a time, comprising: (a) a control unit operatively connected to the modules by a single firing line which carries both power and control signals between said control unit and the modules; and (b) a plurality of selectable firing modules vertically connected one to another to form an elongated assembly suitable for lowering into a well borehole, the assembly including said control unit, with each module, (i) containing at least one charge and where each module is automatically connected one at a time to the firing line in a predetermined sequence to receive power therefrom, and (ii) in response to receipt of power on the firing line, internally generates a module active time interval during which the module and its charge may be selected for firing by said control unit, each module not selected for firing during its active time interval automatically connecting the firing line to the next module in the sequence.

Claim 19

A single-wire selective perforating system for selectively detonating the charges in a plurality of firing modules, one at a time, comprising: (a) a control unit operatively connected to the modules by a single firing line which carries both power and control signals between said control unit and the modules; and (b) a plurality of selectable firing modules vertically connected one to another to form an elongated assembly suitable for lowering into a well borehole, the assembly including said control unit, with each module, (i) containing at least one charge and where each module is automatically connected one at a time to the firing line in a predetermined sequence to receive power therefrom, and (ii) in response to receipt of power on the firing line, internally generates a module active time interval during which the module and its charge may be selected for firing by said control unit, each module not selected for firing during its active time interval automatically connecting the firing line to the next module in the sequence.

Claim 20

The system of claim 17, characterized in that each module, in response to receipt of power on the firing line, then generates during the active time interval an identification signal which uniquely identifies the module.

Claim 21

The system of claim 17 or 18 characterized in that said control unit includes: (a) a means for detecting the amount of power current present on the firing line, thereby to detect when a module has been connected to the firing line; and (b) a means for generating control signals on the firing line including (i) the selection control signal for selecting the module to be selected for firing, (ii) a sequence of arming control signals for connecting the charge in the selected module to the firing line, and (iii) a firing control signal for detonating the charge in the module selected for firing.

Claim 22

The system of claim 19 characterized in that the firing line in each of said firing modules includes an input and an output portion, each said firing module comprising: (a) an identification signal generator responsive to the receipt of power on the input portion of the firing line for generating the identification signal to said control unit indicating that a particular one of said modules has been connected to the firing line; (b) a module active time interval generator responsive to said identification signal generator for generating the module active time interval during which the module may be selected for firing; (c) a stop pulse detector responsive to the selection signal on the input portion of the firing line and to said time interval generator for terminating the generation of the module active time interval and for terminating further module selection; (d) an arming circuit responsive to the sequence of arming control signals and said stop pulse detector for connecting tie charge in the module to the firing line thereby arming the module for firing; and (e) a pass-through switch responsive to said module active time interval generator for connecting at the end of the module active time interval the input portion of the firing line to the output portion thereby connecting power to a next firing module in the assembly.

Claim 23

The system of claim 18, 19 or 20 characterized in that said identification signal generator comprises: (a) a power reset circuit responsive to the receipt of power on the input portion of the firing line for generating a power reset pulse to initiate the active time interval for the module; and (b) a first load connect means responsive to the power reset pulse for generating a predetermined number of pulses on the firing line where the time required to generate the predetermined number of pulses represents the identification signal which uniquely identifies the module.

Claim 24

The system of claim 17 characterized in that the firing line in each of said firing modules includes an input and an output portion, each said firing module comprising: (a) an identification pulse generator responsive to the receipt of power on the input portion of the firing line for generating a pulse indicating that the module has been connected to the firing line; (b) a module active time interval generator responsive to said identification pulse generator for generating the module active time interval during which the module may be selected for firing; (c) a stop pulse detector responsive to a selection pulse on the input portion of the firing line and to said time interval generator for terminating the generation of the module active time interval, and for connecting the charge in the module to the firing line thereby selecting the module for firing; and (d) a pass-through switch responsive to said module active time interval generator for connecting at the end of the module active time interval the input portion of the firing line to the output portion thereby connecting power to a next firing module in the assembly.

Claim 25

The system of claim 20 or 21 characterized in that said identification pulse generator comprises: (a) a power reset circuit responsive to the receipt of power on the input portion of the firing line for generating a power reset pulse to initiate the active time interval for the module; and (b) a load connect means responsive to the power reset pulse for increasing the current on the firing line, the current pulse increase in firing line current representing the identification pulse of the module.

Claim 26

The system of claim 23 characterized in that said firing module active time interval generator comprises: (a) a clocking oscillator for generating a digital time base clocking signal; and (b) a binary counter responsive to said stop pulse detector and the clocking signal for counting a predetermined number of clock pulses to determine the length of the module active time interval, said counter (i) outputting a first signal when a first portion of the time interval has occurred, and (ii) outputting a second signal when a second portion of the time interval has occurred.

Claim 27

The system of claim 24 characterized in that (a) the identification signal is generated during the first portion of the time interval, and (b) the module is enabled to receive a selection pulse during the second portion of the time interval.

Claim 29

The system of claim 26 characterized in that said stop pulse detector comprises: (a) a means for detecting control signals on the input portion of the firing line, a control signal received during the second portion of the active time interval selecting the module for firing; and (b) a disabling means responsive to the detecting means and to said module time interval generator for disabling the clock signals to said binary counter thereby terminating further module sequencing if a selection pulse was received during the second portion.

Claim 30

The system of claim 27 characterized in that the sequence of arming signals includes a first, second and third arming control signal, said arming circuit including: (a) a second load connect means responsive to said stop pulse detector and to the first and second arming signals for generating a pulse of predetermined magnitude to said control unit to indicate that only one module is responding to the arming signals; and (b) a charge connect switch responsive to the third arming signal and said stop pulse detector for connecting the input portion of the firing line to the charge thereby arming the module for firing.

Claim 31

The module of claim 26 characterized in that said stop pulse detection means further includes a zener diode connected between the firing line and said controllable switch for blocking any voltage pulses of less than a predetermined voltage from reaching the charge when the module has been selected for firing, the firing pulse having a voltage amplitude greater than the predetermined voltage.