Downhole tool

Abstract

A hydraulic lock for locking the position of an actuation member of a downhole tool relative to the body of the downhole tool is described. The hydraulic lock comprises first and second fluid chambers fluid communication between which is provided by a first fluid conduit. Located with the first fluid conduit is a first logic controlled valve that is moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers. The hydraulic lock further comprises a secondary control mechanism that provides a second means to selectively permit fluid communication between the first and second chambers. Incorporating the secondary control mechanism within the hydraulic lock provides a means for increasing the reliability and working lifetime of the hydraulic lock. It also provides a means for reducing the risk of unintentional or false activation of the hydraulic lock.

Description

[0001]The present invention relates to downhole tools used in the oil industry. In particular to downhole tools which are activated by remote control for example by sending a pressure signal from the surface to the downhole tool.[0002]In the oil and gas industry within downhole drilling and production completion operations there is a requirement to remotely operate downhole tools and equipment by command or action carried out at surface.[0003]This can be achieved in numerous ways with a variety of actuation arrangements, the most common of which is the use of hydraulic pressure generated in the fluid pumped down the hole through the drilling or production tubular. For example, the pressure of a pumped fluid through a nozzle can be used to apply a force to an actuation member e.g. a piston which in turn activates a downhole tool. Typically these tools may be an expandable underreamer, expandable casing mill, side port circulating tool or similar device.[0004]As fluid circulation is r...

AI Technical Summary

Benefits of technology

The patent describes a system that uses RFID tags to control the operation of a downhole tool. These RFID tags can be used repeatedly without obstructing the flow path and can even be programmed to perform different operations. The system also includes a secondary control mechanism to increase reliability and prevent accidental activation of the downhole tool. This mechanism can be a timer or a logic controlled valve that can automatically unlock the hydraulic lock, allowing for easy resetting of the downhole tool. Overall, this patent provides a more reliable and efficient way to control the operation of downhole tools.

Problems solved by technology

This simple approach, though effective in some applications has a number of disadvantages, namely:there may not be a positive indication at the surface that the activation has taken place;the activation may not be a positive action but happen slowly or partially unless shear pins are employed to ensure that the increased pressure is applied above that required to overcome the spring return force;the activation may only be partial due to seal friction and or other factors such as the ingress of mud solids into the moving parts of the system; andafter activation the tool will de-activate due to force of the return spring whenever and if the flow and pressure is reduced below the threshold pressure.

This actuation arrangement will overcome some of the above disadvantages but introduces others such as:introducing a undesirable restriction into the flow path which could obstruct flow or the passage of other tools;the drop ball will take a considerable time to reach the ball seat, this will have a cost penalty and could have detrimental safety implications; andrepeat operations may not be possible.

There are more complex actuation arrangements currently used in the industry where a number of sequential balls may be dropped to land on a deformable ball seat or releasing mechanism.

These systems do allow a finite number of repeat operations but have been found unreliable in the past and tend to be quite complex.

However RFID tags still suffer the time delay disadvantages of a drop ball system in that they require time to reach the downhole tool.

However, the hydraulic locks of the systems disclosed within international patent application WO 2014 / 009756 are relatively complex and so exhibit the potential for mechanical failure.

Such mechanical failure is particularly problematic when the failure occurs when the downhole tool (e.g. an expandable underreamer or mill) is locked in its deployed configuration as this results it being extremely difficult to subsequently recover the downhole tool from the well.

There is also a risk that the hydraulic locks of these systems may be cause an unintentional or false activation of the downhole tool.

Such accidental activation of the hydraulic lock, and thus the associated downhole tool, could have serious consequences in terms cost and safety for the operator.

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