Downhole device

A device as claimed in any preceding claim, wherein the means to orient the device comprises ballast means eccentrically positioned in the device to favour adoption by the device of one or more orientations rather than others.

A sub as claimed in any preceding claim, wherein the means to orient the device is adapted to orient the device such that the coveying means are in contact with the inner surface of the well-bore.

A device as claimed in any preceding claim, wherein the means to orient the device comprises a portion of the device having a variable radius that favours orientation of the device on a portion of the device having a relatively larger radius.

A device as claimed in any preceding claim, wherein the conveying means comprise one or more of wheels, rollers, skis and endless tracks.

A device as claimed in any preceding claim, wherein conveying means are provided on opposing sides of the device.

A device as claimed in any preceding claim, wherein the conveying means are provided in one or more pairs laterally spaced from one another in a side-by-side arrangement.

A device as claimed in any preceding claim, wherein the conveying means are provided on the lower surface of the device.

A device as claimed in any preceding claim, wherein the conveying means are arranged to contact the well-bore inner surface at or very near the outer circumference of the device.

A device as claimed in any preceding claim, wherein the device is formed with apertures or slots from which the conveying means protrude to engage the inner surface of the well-bore.

A device as claimed in any preceding claim, wherein the conveying means include wheels of large diameter arranged to extend through the body at opposite sides of the device.

As device as claimed in any preceding claim, wherein the conveying means include wheels positioned in pairs side-by-side, with each pair on the same axis through the device.

A device as claimed in any preceding claim, wherein at least some of the conveying means are axially, circumferentially or laterally offset with respect to one another.

A device as claimed in any preceding claim, incorporating a vibrator or oscillator.

A device as claimed in any preceding claim, incorporating a motor to drive one or more of the conveying means, the vibrator and the oscillator.

A device as claimed in any preceding claim, having a sensor coupled to a switch for controlling the movement of the device in the well-bore.

A device as claimed in any preceding claim, having a power source.

A device as claimed in any preceding claim, having separate components in respective subs.

A device as claimed in any preceding claim, having a knuckle or swivel device.

A device as claimed in any preceding claim, having an axial passage for power cables, data cables, control wires, coiled tubing, or other elongate members.

A device as claimed in any preceding claim, having torque transfer means to transfer torque from one end of the device to another and resist relative rotation of the ends of the device.

A downhole tool comprising a sub as claimed in any preceding claim.

A downhole string comprising a device as claimed in any preceding claim.

A downhole device for incorporation into a tool or work string and movement in a well-bore, the device having friction reducing means on its outer surface to facilitate passage of the device through a well-bore.