Apparatus and methods for activating a downhole tool

Abstract

An apparatus for performing a downhole operation in a wellbore comprises a tool string deployed on a slickline into the wellbore, where the tool string comprises a controller and a tool. A motion detector is disposed in the controller and senses motion of the tool string and generates a first signal in response thereto. A device disposed in the controller detects a downhole parameter of interest and generates a second signal in response thereto. A processor in the controller acts according to programmed instructions to activate the tool when the first signal is below a first preset threshold for at least a preset time interval, and the second signal exceeds a second preset threshold. A method of using the apparatus is also provided.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to oil field operations and more particularly to an apparatus and methods for activating a downhole tool.

2. Related Prior Art

A number of operations may be performed in a common oil wellbore by running tools in on a line that is controlled from the surface. In many cases, hardware for logging, perforating, and flow control may be run into the hole on slickline. Slickline commonly comprises a thin, nonelectric cable used for selective placement and retrieval of wellbore hardware. Downhole valves and sleeves can also be adjusted using slickline tools. In many such tools, such as battery powered logging tools, it is desirable to control the turn-on and operation of the tools from the surface. Such tools may contain, for example, caliper arms that contact the borehole wall enable logging tool sensor contact with the formation surrounding the wellbore. These arms must be in a collapsed state during transit to prevent the tool from hanging up on the way into the wellbore. In other instances, such as with perforating guns, it is desirable to prevent their arming and possible firing until they are safely downhole.

Without electrical communication to the surface, prior art tools have used several techniques for actuating such tools downhole. These include raising the bottomhole pressure by a predetermined amount such that a pressure sensor in the downhole tool senses the increased pressure as a signal to actuate. The pressure increase may be in the form of a static increase or in the form of a sequence of pressure pulses that are detected downhole. However, the bottomhole pressure in a well is commonly balanced to hold back formation fluid ingress to the wellbore while not exceeding the fracture pressure of the formation surrounding the wellbore. The increased pressure signal, in many instances, may be sufficient to cause fractures in the formation. Even if the formation does not fracture, the increase pressure in the wellbore may be sufficient to force wellbore fluids to invade the formation and cause errors in subsequent logging operations.

In another prior art downhole tool, a preset time interval is set in a timer in the tool at the surface such that the tool is then deployed to the desired location before the preset time interval has been exceeded. When the preset time interval is exceeded, the tool is activated. Problems in deploying the tool may occur that causes the preset time interval to be exceeded before the tool is properly deployed. Activation of the tool may cause the tool to be stuck in the hole, or cause damage to the wellbore.

There is a demonstrated need for a reliable, safe method of activating slickline tools downhole. The present invention addresses these and other shortcomings of the prior art described above.

SUMMARY OF THE INVENTION

In one aspect of the present invention, an apparatus for performing a downhole operation in a wellbore comprises a tool string deployed on a slickline into the wellbore, where the tool string comprises a controller and a tool. A motion detector is disposed in the controller and senses motion of the tool string and generates a first signal in response thereto. A device disposed in the controller detects a downhole parameter of interest and generates a second signal in response thereto. A processor in the controller acts according to programmed instructions to activate the tool when the first signal is below a first preset threshold for at least a preset time interval, and the second signal exceeds a second preset threshold.

In another aspect, a method of activating a downhole tool in a wellbore comprises deploying a tool string on a slickline into the wellbore. The tool string is held substantially motionless for at least a preset time interval at a location in the wellbore. A motion detector determines that the tool string is substantially motionless for at least the preset time interval. It is determined that a downhole detected parameter of interest exceeds a second preset threshold. A tool is activated in the tool string when both the tool is substantially motionless for at least a preset time interval, and a downhole detected parameter of interest exceeds a second preset threshold.

These and other aspects of the present invention are more clearly described in the drawings and specification that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present invention, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein:

FIG. 1 is a sketch of an exemplary tool string deployed on a slickline;

FIG. 2. is a block diagram of the tool string; and

FIG. 3 is a block diagram depicting an example of the operation of one embodiment of the present invention.

DESCRIPTION

Referring initially to FIG. 1, there is shown an exemplary downhole tool string 11 comprising downhole controller 10 and tool 18. Tool string 11 is supported by slickline 12. Slickline 12 extends from rig 14 at the surface 16. Slickline 12 is deployed from winch 29 around one or more sheave wheels 26, supported from rig 14, and down borehole 20. Surface controller 28 provides suitable power and controls associated with winch 29 for controlling the deployment of the slickline into borehole 20. Alternatively, winch 29 may be separately controlled and surface controller 28 may be a portable computer, such as a personal computer, having appropriate interfaces circuitry to communicate, at the surface, with downhole controller 10. Tool string 11 is deployed adjacent production zone 22 located, for example, near the bottom 24 of borehole 20, also called a wellbore. Borehole 20 commonly has a fluid 13 disposed therein which may be a drilling fluid (also called drilling mud), a production control fluid, and/or a produced fluid from production zone 22. The produced fluid may be water, hydrocarbon liquid, gas, or any combination of the above.

Tool 18 may include multiple downhole tools including but not limited to: a logging tool, a perforating gun, a packer, a flow control valve, and/or any other device suitable for running on slickline 12 and performing downhole operations. The logging tool includes, but is not limited to: an acoustic tool, a density tool, a neutron tool, an induction resistivity tool, an NMR tool, and a gamma ray tool. The logging tool may be a single tool or any combination of such tools, as described above. The downhole tools may be exposed to fluid pressures up to 30,000 psi and temperatures up to 500° F. The downhole fluid may be brine, water based drilling fluid, oil base drilling fluid and/or fluids that may contain hydrogen sulfide, carbon dioxide, methane, and other deleterious compounds.

FIG. 2 is a block diagram of an exemplary embodiment of downhole controller 10 of the present invention. Downhole controller 10 includes processor 31 having sufficient memory therein for storing programmed instructions for operating downhole controller 10 and for storing preset sensor thresholds for use in the present invention. Circuits 32 interface processor 31 with clock 35, motion sensor 33, pressure sensor 34, and temperature sensor 39 and with tool 18. Clock 35 is a crystal oscillator and is used to measure elapsed time from a start signal initiated by surface controller 37 before tool string 11 is deployed in wellbore 20. Clock 35 may be adapted to provide real-time. Motion sensor 33, pressure sensor 34, and temperature sensor 39 are also disposed in controller 10. Motion sensor 33 is used to determine when tool string 11 is motionless. Clock 35 also contains a timer for determining the length of time that the tool is held substantially motionless. In one embodiment, accelerometers 60 are mounted in controller 10 and used to detect motion of tool string 11. Lack of motion is determined when a signal from the accelerometers is below a preset threshold level. It should be noted that the threshold level is somewhat application dependent and is field settable. For example, in a well with fluid flowing past the tool, there will be flow turbulence affecting the accelerometer signal level even when slickline 12 is being held steady at the surface. In a non-flowing well, the accelerometer threshold may be set at a lower level. Alternatively, motion may be detected by a noise sensor 61 that detects the noise associated with the contact of tool string 11 with the wall of wellbore 20 and the flow noise associated with the movement of tool string 11 through either a static or flowing fluid in wellbore 20. Noise sensor 61 may include a piezoelectric crystal and/or a piezoelectric film mounted on controller 10 such that noise sensor 61 is exposed to fluid 13 in wellbore 20. Power source 36 provides power to operate controller 10 and its associated devices. In one embodiment, power source 36 includes batteries (not separately shown) suitable for downhole use. Such batteries are commercially available and are not described here further. Controller 10 is electrically and mechanically coupled to tool 18 using techniques known in the art. Power source 36 contains sufficient power to operate tool 18. Alternatively, tool 18 contains its own separate power source.

Pressure sensor 34 and temperature sensor 39 are mounted in controller 10 such that they are able to measure the steady-state downhole pressure and temperature of fluid 13 in wellbore 20. Such sensors are commercially available and will not be described here.

Processor 31 contains programmed instructions for determining when to activate tool 18. FIG. 3 shows an operational flow chart of an exemplary operation of the present invention. Depending on the particular desired downhole location of interest and the nature of the downhole operation, in step 40, a motion sensor threshold and a length of time that the tool must be motionless are programmed into processor 31 at the surface and prior to deployment into wellbore 20, using a connection to surface processor 28. At least one additional parameter threshold is also downloaded by the operator into processor 31, prior to deployment, using a connection to surface processor 28.

Tool string 11 is deployed into wellbore 20 in step 45. Motion detection is continuous during the entire downhole operation. The tool is stopped and held substantially motionless in step 46. In step 47, the motion detection sensor signal falls below the preset threshold level, and clock 35 begins a separate timer to determine the length of time that the tool is motionless and compare the measured time interval to the preset motionless threshold interval. When the motionless time period exceeds the preset motionless threshold interval, controller 10 proceeds to sense the additional parameter of interest and compare the measurement to its preset threshold value in step 48. The additional parameter may be downhole pressure, downhole temperature, and/or a total deployment time interval. At least one additional parameter is used. However any number or combination of the additional parameters may be used. If all of the criteria are met, then downhole tool 18 is activated in step 49.

In one example, the tool may be programmed to activate when all of the following conditions are met:

• • the motion detector signal remains below the motion threshold for 5 minutes; and
  • the bottomhole pressure is at least 5000 psi; and
  • the bottomhole temperature is at least 80C; and
  • the tool deployment time is at least 90 minutes.
    As seen in this example, the tool may be safely handled at the surface, and activation downhole does not require an increase in bottomhole pressure.

While described above as separate devices, in another embodiment, controller 10 may be included as part of tool 18.

While there has been illustrated and described a particular embodiment of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications, wherein the word “comprising”, as used throughout the claims, is to be interpreted to mean “including but not limited to.”

Claims

1. An apparatus for performing a downhole operation in a wellbore, comprising:

a. a tool string deployed on a slickline into the wellbore, the tool string comprising a controller and a tool;

b. a motion detector disposed in the controller sensing motion of the tool string and generating a first signal in response thereto;

c. a device disposed in the controller detecting a downhole parameter of interest and generating a second signal in response thereto;

d. a processor in the controller acting according to programmed instructions to activate the tool when the first signal is below a first preset threshold for at least a preset time interval and the second signal exceeds a second preset threshold.

2. The apparatus of claim 1, wherein the motion detector is chosen from the group consisting of: an accelerometer and a noise sensor.

3. The apparatus of claim 1, wherein the device is chosen from the group consisting of: a pressure sensor, a temperature sensor, and a downhole clock.

4. The apparatus of claim 1, wherein the second preset threshold is chosen from the group consisting of: a fluid pressure, a fluid temperature, and a deployed time interval.

5. The apparatus of claim 1, wherein the controller comprises:

a. the processor having a memory capable of storing programmed instructions; and

b. a downhole clock.

6. The apparatus of claim 1, wherein the tool is chosen from the group consisting of: a logging tool, a perforating gun, a packer, and a flow control valve.

7. The apparatus of claim 1, wherein the tool comprises a plurality of tools.

8. A method of activating a downhole tool in a wellbore, comprising:

a. deploying a tool string on a slickline into the wellbore;

b. holding the tool string substantially motionless for at least a preset time interval;

c. detecting that the tool string is substantially motionless for at least the preset time interval;

d. determining that a downhole detected parameter of interest exceeds a second preset threshold; and

e. activating a tool in the tool string when both step c. and d. are met.

9. The method of claim 8, wherein, the tool string comprises a controller and a tool.

10. The method of claim 8, wherein the step of detecting that the tool string is substantially motionless comprises determining that a signal from a motion detector is below a first preset threshold at least the preset time interval.

11. The method of claim 10, wherein the motion detector is chosen from the group consisting of: an accelerometer and a noise sensor.

12. The method of claim 8, wherein the downhole detected parameter of interest is chosen from the group consisting of: a downhole fluid pressure, a downhole fluid temperature, and a deployed time interval.

13. The method of claim 8, wherein the tool is chosen from the group consisting of: a logging tool, a perforating gun, a packer, and a flow control valve.

14. The method of claim 8, wherein the tool comprises a plurality of tools.