Downhole activation system

#The invention relates to addressable downhole activation systems.

#To complete a well, one or more sets of perforations may be created downhole using perforating guns. Such perforations allow fluid from producing zones to flow into the wellbore for production to the surface. To create perforations in multiple reservoirs or in multiple sections of a reservoir, multi-gun strings are typically used. A multi-gun string may be lowered to a first position to fire a first gun or bank of guns, then moved to a second position to fire a second gun or bank of guns, and so forth.

#Selectable switches are used to control the firing sequence of the guns in the string. Simple devices include dual diode switches for two-gun systems and concussion actuated mechanical switches or contacts for multi-gun systems. A concussion actuated mechanical switch is activated by the force from a detonation. Guns are sequentially armed starting from the lowest gun using the force of the detonation to set a switch to complete the circuit to the gun above and to break connection to the gun below. The switches are used to step through the guns or charges from the bottom up to select which gun or charge to fire. However, if a switch in the string is defective, then the remaining guns above the defective gun become unusable. In the worst case situation, a defective switch at the bottom of the multi-string gun would render the entire string unusable.

#FIG. 1 is a diagram of a tool string incorporating an embodiment of the invention.

#FIG. 2 is a block diagram of a control unit according to an embodiment used in the tool string of FIG. 1.

#FIG. 3 is a flow diagram of software executed in a system to control activation of devices according to one embodiment.

#Referring to FIG. 1, a perforating system 10 according to an embodiment of the invention for use in a well 12 is illustrated. The perforating system 10 in the illustrated embodiment includes a multi-gun string having a control system that may include multiple control units 14A-14C that control activation of guns or charges in the string. Each control unit 14 may be coupled to switches 16 and 18 (illustrated as 16A-16C and 18A-18C). The cable switches 18A-18C are controllable by the control units 14A-14C, respectively, between on and off positions to enable or disable current flow through one or more electrical cables 20 (which may be located in a wireline or coiled tubing, for example) to successive control units. The switches 16A-16C are each coupled to a detonating device 22 (illustrated as 22A-22C) that may be found in a perforating gun for example. The detonating device may be a standard detonator, a capacitor discharge unit (CDU), or other initiator coupled to initiate a detonating cord to fire shaped charges or other explosive devices in the perforating gun. If activated to an on position, a switch 16 allows electrical current to flow to a coupled detonating device 22.

#In the illustrated embodiment, the switch 18A controls current flow to the control unit 14B, and the switch 18B controls current flow to the control unit 14C. For added safety, a dummy detonator 24 may optionally be coupled at the top of the string. The dummy detonator 24 is first energized and set up before the guns or charges below may be detonated. The dummy detonator 24 includes a cable switch 26 that controls current flow to the first control unit 14A. The dummy detonator 24 also includes a control unit 31 as well as a dummy switch 28, which is not coupled to a detonator.

#The one or more electrical cables 20 extend through a wireline, coiled tubing, or other carrier to surface equipment (generally indicated as 30), which may include a surface system 32, which may be a general-purpose or special-purpose computer, any other microprocessor- or microcontroller-based system, or any control device. The surface system 32 is configurable by tool activation software to issue commands to the downhole tool (e.g., perforating system 10) to set up and to selectively activate one or more of the control units 14.