Apparatus and Methods for Controlling and Communicating with Downhole Devices
Apparatus and methods for controlling and communicating with one or more tools in a downhole tool string including a tractor, an auxiliary tractor tool, a logging tool, a safety sub, a release mechanism, a unit containing sensors for monitoring downhole conditions, a setting tool, and a perforating gun. Also provided are apparatus and methods for controlling and communicating with one or more perforating guns, release devices, and explosive devices in a string to be lowered into a wellbore. Control and communication are accomplished by sending signals from the surface to control switches in the control units on the tool, with redundant switches for safety, to state machines in the respective control units, each state machine returning a signal verifying switch status to the surface. Control and power functions are accomplished with voltage of different polarities for safety.
1 . A switch unit responsive to downlink communication signals for use in a perforating gun, release device, or explosive device for lowering into a wellbore comprising:
a switch for activating the perforating gun, release device, or explosive device;
a microprocessor operably connected to said switch; and
first and second uplink communications transmitters operating at low and high current levels, respectively, said microprocessor selecting either the first or the second current level transmitter depending upon whether downlink communication signals are transmitted before or after lowering into a wellbore.
2 . The apparatus of claim 1 wherein the uplink communications transmitter is selected by either (a) a pre-check controller, surface controller, or surface computer or (b) a pre-check controller, surface controller, and surface computer by downlink communication signals to said microprocessor.
3 . The apparatus of claim 1 wherein said microprocessor conducts a check to determine whether said switch is open or shorted.
4 . The apparatus of claim 1 wherein the second transmitter is selected for uplink communications after lowering the perforating gun, release device, or explosive device into the wellbore.
5 . The apparatus of claim 1 wherein the current level of uplink communications from the first transmitter is in the range of from about 4 milliamps to about 15 milliamps.
6 . The apparatus of claim 1 wherein the current level of uplink communications from the second transmitter is in the range of from about 10 milliamps to about 100 milliamps.
7 . A method of communicating with a switch unit located on a perforating gun, release device, or explosive device for lowering into a wellbore comprising the steps of:
sending a signal to the switch unit;
processing the signal with a state machine comprising the switch unit;
controlling the position of one or more switches comprising the switch unit; and
returning a signal validating switch status from the switch unit at a current level in the range of from about 4 milliamps to about 15 milliamps.
8 . The method of claim 7 wherein the return signal further comprises the state of the switch unit.
9 . The method of claim 7 wherein the return signal further comprises an identifier for the switch unit.
10 . The method of claim 7 additionally comprising the step of lowering the perforating gun, release device, or explosive device into the wellbore and returning a signal from the switch unit at a current level in the range of from about 10 milliamperes to about 100 milliamperes.
11 . The method of claim 7 additionally comprising the step of confirming switch status before changing switch position.
12 . An explosive initiator integrated into a switch unit for use in connection with a perforating gun to be lowered into a wellbore on a cable comprising:
means for receiving a downlink signal through a cable to which a perforating gun is to be lowered into a wellbore;
first and second transmitters operating at low and high current levels for transmitting uplink signals through the cable;
a microprocessor in electrical communication with said signal receiving means and said first and second transmitters including a state machine for validating a signal from said signal receiving means and for returning an uplink signal using either said first or said second transmitter through the cable;
a switch responsive to an output from said microcontroller when a signal is validated by the state machine; and
an explosive initiator operably connected to said switch.
13 . The explosive initiator of claim 12 additionally comprising means for checking the status of the switch.
14 . The explosive initiator of claim 12 wherein said first and second transmitters transmit uplink signals at different current levels.
15 . The explosive initiator of claim 14 wherein the current level of the uplink signal is controlled from a surface computer.
16 . The method of claim 12 wherein the uplink signal further comprises the state of the switch unit.
17 . The method of claim 12 wherein the uplink signal further comprises an identifier for the switch unit.
18 . A method of switching between a safe mode for tractoring and a perforating mode for perforating in a tool string including a tractor and a perforating gun for lowering into a wellbore on a wireline comprising the steps of:
sending a signal to a control unit on the tractor from the surface;
the control unit comprising a state machine for processing the signal and controlling the position of a switch for connecting the wireline to either the tractor motor or a through wire connecting to the perforating gun while blocking negative voltage through the wireline; and
returning a signal validating switch position to the surface.
19 . The method of claim 18 wherein the tool string additionally includes a safety sub between the tractor and the perforating gun and negative voltage is blocked at the output of the safety sub.
20 . The method of claim 18 additionally comprising the step of checking switch position before connecting the wireline to the tractor.
21 . The method of claim 18 wherein the return signal comprises an identifier for the control unit.
22 . The method of claim 18 wherein the return signal comprises the state of the control unit.