Method and apparatus for performing a survey of tubing which is stuck in a borehole, e.g. for determining a free point

An assembly for performing a survey of tubing which is stuck in a borehole for determining a location at which the tubing may, or may not, be subjected to at least one operation for freeing the tubing or a portion thereof, the assembly comprising:

• a tractor for advancing the assembly along the tubing on an inside thereof;
• first and second parts and a connection connecting the first and second parts for allowing either or both longitudinal and rotational movement of the first part relative to the second part;
• at least one tractor wheel connected to the first part, and at least one tractor wheel connected to the second part;
• wherein in an operational configuration, the tractor wheels are arranged longitudinally apart for contacting respective locations on a wall of the tubing,
• wherein the tractor wheels are operable to rotate and drive the assembly along the tubing when in contact with the wall,
• wherein the tractor wheels are configured to couple between the wall and the respective first and second parts of the assembly when in contact with the wall, such that a stimulus applied to the tubing producing twisting and/or longitudinal compression or extension in a length of the tubing between the respective contact locations on the wall can be communicated to produce a response which comprises either or both of the longitudinal and the rotational relative movement between the first and second parts of the assembly;
• and
• a detector for detecting the response, for producing data to determine the location at which the tubing may, or may not, be subjected to the operation for freeing the tubing or the portion thereof.

A method of performing a survey of tubing which is stuck in a borehole, the method comprising the steps of:

• a. deploying an assembly including a tractor inside the tubing, the assembly having first and second parts that are connected through a connection that allows either or both longitudinal and rotational movement of the first part relative to the second part, wherein at least one tractor wheel is connected to the first part, and at least one tractor wheel is connected to the second part, the tractor wheels being arranged longitudinally apart and in contact against a wall of the tubing;
• b. advancing the assembly along the tubing using the tractor;
• c. applying a stimulus comprising a component of force to the tubing, the component of force comprising any one or more of:
• torque about a longitudinal axis of the tubing;
• tension along the longitudinal axis;
• and
• compression along the longitudinal axis;
• the assembly being coupled to the wall of the tubing by the tractor wheels, twisting and/or longitudinal compression or extension produced in a length of the tubing between the locations of contact of the tractor wheels on the wall producing a response which comprises either or both of said longitudinal and said rotational relative movement between the first and second parts of the tractor;
• d. detecting the response, obtaining data dependent upon the response;
• and
• e. using the data to determine the location at which the tubing may, or may not, be subjected to at least one operation for freeing the tubing or a portion thereof.

A method of performing a survey and freeing tubing or a portion thereof, said tubing or portion to be freed being stuck in a borehole, the method comprising the steps of:

• (a) providing an assembly including a tractor and at least one tool inside the tubing;
• (b) surveying the tubing by:
• i. advancing the assembly along the tubing;
• ii. applying the stimulus to the tubing, the assembly being coupled to the wall of the tubing by the tractor wheels;
• and
• iii. detecting the response comprising either or both longitudinal and rotational relative movement between the first and second parts of the tractor, to determine the location at which the tubing is to be subjected to at least one operation so as to allow the tubing or a portion thereof to be freed;
• (c) freeing the tubing or the portion thereof, using the tool at the identified location to perform said operation;
• and
• (d) pulling the freed tubing or portion thereof along the borehole.

A tractor for use in an assembly for performing a survey of a tubing which is stuck in a borehole, the assembly configured to be advanced along the tubing on an inside thereof by means of the tractor, the tractor comprising:

• first and second parts and a connection connecting the first and second parts for allowing either or both longitudinal and rotational movement of the first part relative to the second part;
• at least one tractor wheel connected to the first part, and at least one tractor wheel connected to the second part;
• wherein in an operational configuration, the tractor wheels are arranged longitudinally apart for contacting respective locations on a wall of the tubing,
• wherein the tractor wheels are configured to couple between the wall and the respective first and second parts of the assembly when in contact with the wall, such that a stimulus applied to the tubing producing twisting and/or longitudinal compression or extension in a length of the tubing between the respective contact locations on the wall can be communicated to produce a response comprising either or both the longitudinal and the rotational relative movement between the first and second parts of the tractor;
• and
• a detector for detecting the response for obtaining data to determine the location at which the string of tubing may, or may not be subjected to at least one operation for freeing the tubing or a portion thereof.