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.
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.
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:
Referring initially to
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.
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.
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:
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.”