Single-wire selective performation system

Claims

What is claimed is:

1. 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 comprising 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.

2. The method of claim 1 wherein 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) generating from the module just connected to the firing line power an identification pulse to indicate to said control unit that a next module has been connected to the firing line power;

(d) controlling at the end of each module active time interval a pass-thru switch to pass the firing line power to the next module in the sequence if the module was not selected; and

(e) repeating steps (b)-(d) until the module to be selected is generating an active time interval wherein said control unit may generate a selection pulse to select the module for firing thereby terminating further sequencing of the modules.

3. The method of claim 2 wherein the step of generating a module active time interval comprises the step of generating a time interval having,

(a) a first portion during which the module generates the identification pulse, and

(b) a second portion during which the module is enabled to receive a selection pulse from said control unit to select the module for firing.

4. The method of claim 2 wherein 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.

5. The method of claim 4 wherein the identification pulse for each module must occur within a predetermined time window from the occurrence of the last identification pulse.

6. The method of claims 1, 3 or 5 further including the step of grounding the shot in each module that was connected to but not selected by said control unit.

7. The method of claim 6 further including 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.

8. The method of claim 7 further including the step of generating a power reset in each module when each module is connected to the firing line power thereby initiating the active time interval for that module.

9. The method of claim 3 wherein the first and second portions of each active time interval are equal in length.

10. In a single-line selective perforating system having a firing control means, a plurality of modules connected in a string adapted for insertion into a well borehole where each module is connected one to the other from a lowermost to an uppermost module with each module containing at least one shaped charge or shot for perforating a well casing into the subsurface formations, and a controllable pass-through switch means for passing a single firing line to the next lower module in the string, a method of selecting a module to be fired comprising the steps of:

(a) applying to the firing line electrical power having voltage and current of sufficient magnitude to power the modules but without sufficient power to fire a shot;

(b) generating internal to the module last connected to the firing line power a module active time interval during which the module may be selected for firing by a selection signal, the modules automatically sequencing to another module at the end of each time interval;

(c) generating during each module active time interval an identifying pulse to identify to the firing control means that a next module has been connected to the firing line; and

(d) generating during a module active time interval a selection pulse if the active module is to be selected whereby the module is selected for firing by a firing pulse of sufficient power on the firing line to detonate a shot.

11. The method of claim 10 further including the step of controlling said pass-through switch means in the last connected module at the end of its module active time interval to connect the next lower module in the string to the firing line if that module was not selected thereby powering up the next lower module.

12. The method of claim 10 wherein said step of generating a module active time interval includes the steps of:

(a) generating a first portion of the active time interval during which the identification pulse of the module is generated to said control means; and

(b) generating a second portion of the active time during which the module is enabled to receive the selection signal to select the module.

13. The method of claim 10 or 12 wherein said identification pulse is a current pulse on the firing line whose incremental change in the current level must fall within a predetermined level for the control means to select and fire the module.

14. The method of claim 13 wherein the identification pulse for the next module connected to the firing line must occur within a predetermined time window of the previous identification pulse on the firing line.

15. The method of claim 14 further including the step of firing a shot by applying a power pulse on the firing line of sufficient energy to detonate the shot in the module which has been selected for firing.

16. The method of claim 12 wherein the step of generating a module active time for each module includes the step of generating a power reset pulse in the module when a module is first connected to the firing line power.

17. The method of claim 16 wherein each module connected to the firing line but not selected remains connected to the firing line in an inactive state, and where the modules in an inactive state may be reset to once again be sequenced by momentarily removing the power from the firing line.

18. In a single-firing line selective perforating system for detonating a plurality of charges in a shot string comprised of a plurality of series connected firing modules, each firing module containing a charge to be detonated by application of a firing pulse on the firing line, and each module electrically powered by power signals from the firing line, a method of selecting and firing the modules comprising the steps of:

(a) generating internal to each module as each module is connected, one at a time in a sequence to the firing line power signals, a module active time interval having a first and a second portion;

(b) generating in each module during the first portion an identifying pulse of predetermined amplitude to identify that the module has been connected to the firing line;

(c) connecting the next module in the string to receive power to the firing line at the end of the second portion of the module active time interval for the module last connected to the firing line; and

(d) generating during the second portion of the active time for the module to be selected a pulse to select and arm the module, the module so selected remaining selected until fired or reset.

19. The method of claim 18 further including the step of connecting to the firing line the detonation portion of the charge in the module selected to be fired in response to the selection and arming pulse whereby the firing pulse on the firing line can detonate the selected charge.

20. The method of claims 18 or 19 wherein the identification pulse for each module must

(a) have an amplitude which lies in a predetermined range, and

(b) occur within a predetermined time window measured from the occurrence of the last identification pulse on the firing line.

21. In a single-line selective perforating system having a single firing line for connecting a control unit to a plurality of shot modules, each adapted to be electrically connected in a predetermined sequence to the firing line where each connected module receives both power and firing control signals from the control unit over the firing line, a method of selecting a module for firing from among the plurality of modules 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.

22. The method of claim 21 wherein 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.

23. The method of claim 21 wherein 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.

24. The method of claim 23 wherein the identification pulse for each module must occur within a predetermined time window measured from the occurrence of the last identification pulse.

25. The method of claims 21, 22 or 24 further including the step of grounding the shot in each module that was connected to but not selected by the control unit.

26. The method of claim 25 further including 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.

27. The method of claim 26 further including the step of generating a power reset in each module when each modue is connected to the firing line thereby initiating each active time interval.

28. The method of claim 22 wherein the first and second portions of each active time interval are equal in length.

29. 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, 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.

30. The system of claim 29 wherein said control unit includes:

(a) a means for detecting the amount of power current present on the firing line, thereby to detect when each module has been connected to the firing line; and

(b) a means for generating control signals on the firing line including

(i) a selection control signal for selecting a module for firing during the active time interval for the module last connected to the firing line, and

(ii) a firing control signal for detonating the charge in the module selected for firing.

31. The system of claims 29 or 30 wherein 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 con nected 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.

32. The system of claim 31 wherein 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.

33. The system of claim 31 wherein 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.

34. The system of claim 33 wherein

(a) the identification pulse 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.

35. The system of claim 33 wherein said stop pulse detector comprises:

(a) a means for detecting an increase in voltage on the input portion of the firing line, an increase in voltage during the second portion of the active time interval representing the selection pulse;

(b) a disabling means responsive to the detecting means and to said module time interval generator for disabling the clocking signals to said binary counter and for generating a firing switch signal if a selection pulse is detected by said detecting means during the second portion of the module active time interval; and

(c) a controllable switch responsive to the firing switch signal for connecting the input portion of the firing line to the charge in said firing module.

36. The module of claim 35 wherein 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.

37. A firing module for use in a single-wire selective perforating system, the system having a plurality of said firing modules vertically connected to form an elongated assembly suitable for lowering into a well borehole, and includes a control means for generating power and control signals on a single firing line connectable to each of said modules, each firing module comprising:

(a) at least one shot, each shot including a detonator responsive to a firing pulse from said control means for detonating its associated shot;

(b) an identification pulse generator responsive to the receipt of power on the firing line for generating a current pulse on the firing line indicating that the module has been connected to the firing line;

(c) a module active time interval generator responsive to said identification pulse generator for generating a module active time interval during which the module may be selected for firing by said control means;

(d) a stop pulse detector responsive to a selection pulse on the firing line and to said time interval generator for terminating the generation of the module active time interval, and for connecting said detonator to the firing line thereby selecting the module for firing; and

(e) a pass-through switch responsive to said module active time interval generator for passing the power on the firing line through the module at the end of the module active time interval thereby providing power to another module in the assembly.

38. The module of claim 37 wherein said identification pulse generator comprises:

(a) a power reset circuit responsive to the receipt of power on the firing line for generating a power reset pulse to initiate the start of the module active time interval; and

(b) a load connect means for connecting a load to the firing line thereby increasing the current on the firing line, the pulse increase in firing line current representing the i