Abstract: A downhole tool (1) comprises a power control module (20), which includes a battery pack (22) for supplying power to components of the tool, and an electronic control circuit (24) for controlling the supply of power by the battery pack. The electronic control circuit (24) and battery pack (22) are contained within a housing (26) that allows their insertion and removal as a single unit. The tool (1) also comprises an electric motor (104) for powering a gear assembly (210), and a braking system comprising an electrical and a magnetic brake for braking the motor (104) when required.

Abstract: A roller tool 1 that can be connected into a string for deployment into an oil or gas well includes at least two rollers or wheels 10 located on each side of the roller tool 1, with axes of rotation that are perpendicular to the axis of the roller tool 1. The roller tool further includes at least two interconnecting tubular portions, where one tubular portion 41 comprises a mandrel 45 that connects to another tubular portion 42. An annular hub 20 is fitted over the mandrel 45 and the rollers 10 are connected onto the hub 20. The tubular portions 41, 42 comprise circumferential sleeve sections 56a, 56b that partially extend over the rollers 10 and resist detachment of the rollers 10 from the roller tool 1. The roller tool 1 can aid passage of a string through a well by holding the string away from the walls of the well and reducing frictional contact.