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A perforating gun assembly for use in a subterranean well incorporates therein an electromagnetic frequency receiver coupled to a motor section which, in turn, is coupled to the mechanically actuatable firing head portion of the perforating gun. The assembly is lowered into a cased wellbore to a sub

A perforating gun assembly for use in a subterranean well incorporates therein an electromagnetic frequency receiver coupled to a motor section which, in turn, is coupled to the mechanically actuatable firing head portion of the perforating gun. The assembly is lowered into a cased wellbore to a subterranean formation location, and a surface-disposed transmitter generates encoded electromagnetic waves through the earth to the receiver. Upon sensing in the received waves a predetermined frequency and embedded firing code, the receiver electrically operates the motor which, in turn, mechanically actuates the firing head to initiate the firing of the perforating gun. While the assembly is illustratively lowered into the wellbore on a tubing structure, a variety of non-tubing structures may be alternatively utilized to lower the gun assembly into the wellbore and operatively support it therein.

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1. A method of operating an actuatable well tool, the method comprising the steps of:placing the tool in a subterranean well bore;providing a receiver operable to detect electromagnetic waves propagated through the earth and having a circuit board portion with a main CPU portion adapted to receive a

1. A method of operating an actuatable well tool, the method comprising the steps of:placing the tool in a subterranean well bore;providing a receiver operable to detect electromagnetic waves propagated through the earth and having a circuit board portion with a main CPU portion adapted to receive an electromagnetic wave detection signal and a ground signal and responsively generate an actuation request signal, and an auxiliary fail-safe CPU portion operative to receive the actuation request signal, monitor selected parameters of the tool to detect whether system errors exist, and responsively generate an actuation signal only in the absence of sensed system errors;propagating electromagnetic waves through the earth;detecting the electromagnetic waves; andactuating the tool in response to the detection of the electromagnetic waves and generation of the actuation signal. 2. The method of claim 1 wherein:the placing step is performed by lowering the tool into the wellbore on a tubing structure. 3. The method of claim 1 wherein:the placing step is performed by placing a mechanically actuatable well tool in the wellbore. 4. The method of claim 1 wherein:the placing step is performed by placing a perforating gun in the well bore. 5. The method of claim 4 wherein:the placing step is performed by placing a mechanically actuatable perforating gun in the wellbore. 6. The method of claim 1 wherein:the propagating step is performed by propagating electromagnetic waves having square configurations through the earth. 7. The method of claim 6 wherein:the propagating step is performed by propagating electromagnetic waves having modulated square configurations through the earth. 8. The method of claim 1 wherein:the propagating step is performed by propagating electromagnetic waves having a frequency of approximately 15 Hz or less through the earth. 9. The method of claim 1 further comprising the step of:encoding an actuation address in the electromagnetic waves. 10. A method of operating an actuatable well tool, the method comprising the steps of:providing a sensor for sensing a predetermined downhole parameter;providing a well tool assembly including the well tool, an electromagnetic frequency receiver, an actuation section, and a transmitter operative to transmit through the earth to a surface-disposed receiver first electromagnetic waves indicative of the value of the sensed parameter, the well tool being a mechanically actuatable well tool;lowering the well tool assembly into a subterranean wellbore;propagating second electromagnetic waves through a portion of the earth externally adjacent the wellbore; andutilizing the well tool assembly receiver to detect the second electromagnetic waves in the earth and responsively cause the actuation section to actuate the well tool,mechanically actuatable well tool being a perforating gun. 11. A method of operating an actuatable well tool, the method comprising the steps of:providing a sensor for sensing a predetermined downhole parameter;providing a well tool assembly including the well tool, an electromagnetic frequency receiver, an actuation section, and a transmitter operative to transmit through the earth to a surface-disposed receiver first electromagnetic waves indicative of the value of the sensed parameter;lowering the well tool assembly into a subterranean wellbore;propagating second electromagnetic waves through a portion of the earth externally adjacent the wellbore;utilizing the well tool assembly receiver to detect the second electromagnetic waves in the earth and responsively cause the actuation section to actuate the well tool; andencoding an actuation address in the second electromagnetic waves. 12. The method of claim 11 wherein:the well tool is a mechanically actuatable well tool. 13. The method of claim 11 wherein:the lowering step is performed by securing the well tool assembly to a tubing structure and then lowering the tubing structure into the wellbore. 14. The method of cla im 11 wherein:the propagating step is performed by propagating electromagnetic waves having square configurations through the earth. 15. The method of claim 11 wherein:the propagating step is performed by propagating electromagnetic waves having sine or cosine configurations through the earth. 16. The method of claim 11 wherein:the propagating step is performed by propagating electromagnetic waves having a frequency of approximately 15 Hz or less through the earth. 17. A subterranean well comprising:a wellbore extending through the earth; anda well tool assembly disposed in the wellbore and including:an actuatable well tool,a receiver operable to detect electromagnetic waves propagated through the earth and responsively generate a signal, the receiver having a circuit board portion with a main CPU portion adapted to receive an electromagnetic wave detection signal and a ground signal and responsively generate an actuation request signal, and an auxiliary fail-safe CPU portion operative to receive the actuation request signal, monitor selected parameters of the well tool assembly to detect whether system errors exist, and responsively generate the first-mentioned signal only in the absence of sensed system errors, andan actuation structure operable to receive the first-mentioned signal and responsively actuate the tool. 18. The subterranean well of claim 17 wherein:the actuatable well tool is a mechanically actuatable well tool. 19. The subterranean well of claim 18 wherein:the mechanically actuatable well tool is a perforating gun having a mechanically actuatable firing head portion. 20. The subterranean well of claim 18 wherein:the actuation structure includes a motor operative to mechanically actuate the well tool. 21. The subterranean well of claim 20 wherein:the motor has an output member translatable in a selectively variable direction through a selectively adjustable stroke. 22. The subterranean well of claim 17 further comprising:a transmitter operative to propagate electromagnetic waves through a portion of the earth externally adjacent the wellbore. 23. The subterranean well of claim 22 wherein:the electromagnetic waves have square configurations. 24. The subterranean well of claim 23 wherein:the electromagnetic waves are modulated square waves. 25. The subterranean well of claim 22 wherein:the electromagnetic waves have a frequency of approximately 15 Hz or less. 26. The subterranean well of claim 22 wherein:the electromagnetic waves have an actuation address encoded therein. 27. The subterranean well of claim 17 wherein:the receiver is operable to generate the signal in response to detecting electromagnetic waves propagated through the earth and having both a predetermined frequency and encoded actuation address. 28. The subterranean well of claim 17 wherein:the well tool assembly is suspended on a tubing structure extending into the wellbore. 29. A subterranean well comprising:a wellbore extending through the earth; anda well tool assembly disposed in the wellbore and including:an actuatable well tool,a receiver operable to detect electromagnetic waves propagated through the earth and responsively generate a signal, andan actuation structure operable to receive the signal and responsively actuate the tool,the wellbore being lined with a metal casing having a first portion, and a second portion longitudinally spaced apart from the first portion in a downhole direction,the receiver having a control circuitry portion, andthe well tool assembly having first and second electrically conductive paths which are insulatively isolated from one another and are respectively operative to (1) transmit an electromagnetic wave signal from the first casing portion to the control circuitry portion, and (2) connect a ground reference from the second casing portion to the control circuitry portion. 30. The subterranean well of claim 29 wherein:the well tool assembly has an elongated, electrically conductive tubular outer body portion and a generally coaxially extending electrically conductive tubular inner body portion, each of the outer and inner body portions having insulative gaps formed therein between adjacent longitudinal sections thereof. 31. The subterranean well of claim 30 wherein:the adjacent longitudinal sections of the tubular outer body portion having axially spaced apart threaded end portions threadedly connected to an annular collar member at thread joints containing an electrically insulative material defining spaced apart insulation gaps between the longitudinal sections of the outer body portions and electrically isolating them from one another. 32. A well tool assembly operatively positionable in a subterranean wellbore and comprising:an actuatable well tool;a receiver operable to detect electromagnetic waves propagated through the earth and responsively generate a signal, the receiver having a circuit board portion with a main CPU portion adapted to receive an electromagnetic wave detection signal and a ground signal and responsively generate an actuation request signal, and an auxiliary fail-safe CPU portion operative to receive the actuation request signal, monitor selected parameters of the well tool assembly to detect whether system errors exist, and responsively generate the first-mentioned signal only in the absence of sensed system errors; andan actuation structure operative to receive the first-mentioned signal and responsively actuate the tool. 33. The well tool assembly of claim 32 wherein:the actuable well tool is a mechanically actuatable well tool. 34. The well tool assembly of claim 33 wherein:the mechanically actuatable well tool is a perforating gun having a mechanically actuatable firing head portion. 35. The well tool assembly of claim 33 wherein:the actuation structure includes a motor operative to mechanically actuate the well tool. 36. The well tool assembly of claim 35 wherein:the motor has an output member translatable in a selectively variable direction through a selectively adjustable stroke. 37. The well tool assembly of claim 32 wherein:the receiver is operable to generate the signal in response to detecting electromagnetic waves propagated through the earth and having both a predetermined frequency and encoded actuation address. 38. A well tool assembly operatively positionable in a subterranean wellbore and comprising:an actuatable well tool;a receiver operable to detect electromagnetic waves propagated through the earth and responsively generate a signal; andan actuation structure operative to receive the signal and responsively actuate the tool,the receiver having a control circuitry portion, andthe well tool assembly having first and second electrically conductive paths which are insulatively isolated from another and are respectively operative to (1) transmit a received electromagnetic wave signal to the control circuitry portion, and (2) transmit a received ground signal to the control circuitry portion. 39. The well tool assembly of claim 38 wherein:the well tool assembly has an elongated, electrically conductive tubular outer body portion and a generally coaxially extending electrically conductive tubular inner body portion, each of the outer and inner body portions having insulative gaps formed therein between adjacent longitudinal sections thereof. 40. The well tool assembly of claim 39 wherein:the adjacent longitudinal sections of the tubular outer body portion having axially spaced apart threaded end portions threadedly connected to an annular collar member at thread joints containing an electrically insulative material defining spaced apart insulation gaps between the longitudinal sections of the outer body portions and electrically isolating them from one another. 41. A perforating gun assembly operatively positionable in a subterranean wellbore and comprising:a perforating gun having a mechanically actuatable firing head portion;an actuating section connected to the firing head and including a motor operable to engage and mechanically actuate the firing head portion;a receiver connected to the actuating section and being operative to detect electromagnetic waves propagated through the earth and responsively operate the motor; anda sensor operative to sense a downhole parameter; anda transmitter operative to transmit electromagnetic waves indicative of the value of the sensed downhole parameter. 42. A method of perforating a subterranean wellbore casing, the method comprising the steps of:lowering spaced apart perforating gun assemblies through the wellbore to a portion of the casing to be perforated, each perforating gun assembly including a perforating gun having a mechanically actuatable firing head, a motor control section connected to the firing head, and an electromagnetic frequency receiver connected to the motor control section, each receiver having a circuit board portion with a main CPU portion adapted to receive an electromagnetic wave detection signal and a ground signal and responsively generate an actuation request signal, and an auxiliary fail-safe CPU portion operative to receive the actuation request signal, monitor selected parameters of the associated perforating gun assembly to detect whether system errors exist, and responsively generate a firing signal only in the absence of sensed system errors;propagating electromagnetic waves through a portion of the earth externally adjacent the casing; andutilizing the receivers to detect the electromagnetic waves and sequentially fire the perforating guns in a preselected order. 43. For use in a subterranean wellbore, a method of operating a plurality of well tool assemblies, the method comprising the steps of:lowering spaced apart well tool assemblies through the wellbore to a predetermined portion of the wellbore, each well tool assembly including a mechanically actuatable well tool, a motor section connected to the well tool, and an electromagnetic frequency receiver connected to the motor section;propagating electromagnetic waves through a portion of the earth externally adjacent the casing;utilizing the receivers to detect the electromagnetic waves and sequentially actuate the well tools in a preselected order;providing a sensor operative to sense a predetermined downhole parameter; andproviding a transmitter operative to transmit through the earth to a surface-disposed receiver electromagnetic waves indicative of the value of the sensed parameter. 44. A subterranean well comprising:a wellbore extending through the earth; anda spaced apart plurality of well tool assemblies disposed in the wellbore and being selectively actuatable in a predetermined sequence, each well tool assembly including an actuatable well tool, a receiver operable to detect electromagnetic waves propagated through the earth and responsively generate a signal, and an actuation structure operable to receive the signal and responsively actuate the tool, the receiver having a circuit board portion with a main CPU portion adapted to receive an electromagnetic wave detection signal and a ground signal and responsively generate an actuation request signal, and an auxiliary fail-safe CPU portion operative to receive the actuation request signal, monitor selected parameters of the well tool assembly to detect whether system errors exist, and responsively generate the first-mentioned signal only in the absence of sensed system errors. 45. The subterranean well of claim 44 wherein:the well tools are mechanically actuatable. 46. The subterranean well of claim 44 wherein:at least one of the well tools is a perforating gun. 47. The subterranean well of claim 44 wherein at least one of the well tools is a mechanically actuatable perforating gun. 48. A subterranean well comprising:a wellbore extending through the earth; anda well tool assembly disposed in the wellbore and including:a mechanically actuatable well tool,a receiver operable to detect first electromagnetic waves propagated through t he earth and responsively generate a signal,an actuation structure operable to receive the signal and responsively actuate the tool,a sensor for sensing a predetermined downhole parameter, anda transmitter operative to transmit directly through the earth to a surface-disposed receiver second electromagnetic waves indicative of the value of the sensed parameter,the mechanically actuatable well tool being a perforating gun have a mechanically actuatable firing head portion. 49. A subterranean well comprising:a wellbore extending through the earth; anda well tool assembly disposed in the wellbore and including:a mechanically actuatable well tool,a receiver operable to detect first electromagnetic waves propagated through the earth and responsively generate a signal,an actuation structure operable to receive the signal and responsively actuate the tool,a sensor for sensing a predetermined downhole parameter, anda transmitter operative to transmit directly through the earth to a surface-disposed receiver second electromagnetic waves indicative of the value of the sensed parameter,the actuation structure including a motor operative to mechanically actuate the well tool. 50. The subterranean well of claim 49 wherein:the motor has an output member translatable in a selectively variable direction through a selectively adjustable stroke. 51. A subterranean well comprising:a wellbore extending through the earth;a well tool assembly disposed in the wellbore and including:an actuatable well tool,a receiver operable to detect first electromagnetic waves propagated through the earth and responsively generate a signal, andan actuation structure operable to receive the signal and responsively actuate the tool,the subterranean well further comprising a sensor for sensing a predetermined downhole parameter, anda transmitter operative to transmit directly through the earth to a surface-disposed receiver second electromagnetic waves indicative of the value of the sensed parameter; anda transmitter operative to propagate the first electromagnetic waves, through a portion of the earth externally adjacent the wellbore, to the well tool assembly receiver,the first electromagnetic waves having an actuation addredd encoded therein. 52. The subterranean well of claim 51 wherein:the first electromagnetic waves have square configurations. 53. The subterranean well of claim 52 wherein:the first electromagnetic waves are modulated square waves. 54. The subterranean well of claim 51 wherein:the first electromagnetic waves have a frequency of approximately 15 Hz or less. 55. A subterranean well comprising:a wellbore extending through the earth; anda well tool assembly disposed in the wellbore and including:an actuatable well tool,a receiver operable to detect first electromagnetic waves propagated through the earth and responsively generate a signal,an actuation structure operable to receive the signal and responsively actuate the tool,a sensor for sensing a predetermined downhole parameter, anda transmitter operative to transmit directly through the earth to a surface-disposed receiver second electromagnetic waves indicative of the value of the sensed parameter,the well tool assembly receiver being operable to generate the signal in response to detecting electromagnetic waves propagated through the earth and having both a predetermined frequency and encoded actuation address. 56. A well tool assembly operatively positionable in a subterranean wellbore and comprising:an mechanically actuatable well tool;a receiver operable to detect first electromagnetic waves propagated through the earth and responsively generate a signal;an actuation structure operative to receive the signal and responsively actuate the tool;a sensor for sensing a predetermined downhole parameter; anda transmitter operative to transmit directly through the earth to a surface-disposed receiver second electromagnetic waves indicative of the value of the sensed parameter,the mechanically actuat able well tool being a perforating gun having a mechanically actuatable firing head portion. 57. A well tool assembly operatively positionable in a subterranean wellbore and comprising:an mechanically actuatable well tool;a receiver operable to detect first electromagnetic waves propagated through the earth and responsively generate a signal;an actuation structure operative to receive the signal and responsively actuate the tool;a sensor for sensing a predetermined downhole parameter; anda transmitter operative to transmit directly through the earth to a surface-disposed receiver second electromagnetic waves indicative of the value of the sensed parameter,the actuation structure including a motor operative to mechanically actuate the well tool. 58. The well tool assembly of claim 57 wherein:the motor has an output member translatable in a selectively variable direction through a selectively adjustable stroke. 59. A well tool assembly operatively positionable in a subterranean wellbore and comprising:an actuatable well tool;a receiver operable to detect first electromagnetic waves propagated through the earth and responsively generate a signal;an actuation structure operative to receive the signal and responsively actuate the tool;a sensor for sensing a predetermined downhole parameter; anda transmitter operative to transmit directly through the earth to a surface-disposed receiver second electromagnetic waves indicative of the value of the sensed parameter;the well tool assembly receiver being operable to generate the signal in response to detecting electromagnetic waves propagated through the earth and having both a predetermined frequency and encoded actuation address.