In many fields it is desirable to support and move equipment with the assistance of some form of transport assembly, such as for example, a roller or wheel assembly. In the oil and gas industry, such transport assemblies are of particular use in connection with the deployment: of wellbore apparatus, such as tool strings, tubing strings or other equipment which may need to be deployed and transported into position in a wellbore for different operations.
In the case of a deviated wellbore where a longitudinal axis of the wellbore is non-vertical (and sometimes horizontal), gravity tends to force the string toward a lower wall of the wellbore, leading to high friction between the wall of the wellbore and the string. In such circumstances, it can be a particular challenge to move a string through the wellbore, and roller-based transport assemblies are of particular use to provide stand off of the string from the wellbore wall and to facilitate low friction transport of the string through the well.
Such transport assemblies have a “roller” that contacts the wellbore wall and provides support for the string to keep sections of the string off the wall easing resistance against the string. In addition, the roller may turn on engagement with the wellbore wall.
There are a number of difficulties associated with existing transport assemblies for downhole apparatus. High temperatures and pressures often persist downhole, and wellbore fluids carrying mud rock cuttings are often circulated through the well. This presents a harsh, environment which can cause, wear on equipment. Also, the working environment on site both onshore and offshore can also be demanding. Often, space is limited and strict safety guidelines must be followed. The weather conditions may also present difficulties to personnel. In these conditions, existing equipment can be difficult and inconvenient to handle and maintain. Site operations can therefore be time consuming and costly.
It is amongst the aims of the present invention to obviate or at least mitigate shortcomings of existing transport assemblies.