Apparatus and methods for orienting, stabilising or stably operating a logging tool

A logging tool, toolstring (10), or element (19) comprises a stabilizer including a pair of moveable, rigid, main stabilizer arms (23, 24) that each is pivotably secured adjacent to one another at one end to the logging tool or toolstring. As a result the arms (23, 24) are moveable between a relatively retracted position on the one hand and a relatively advanced position on the other in which the main stabilizer arms diverge from one another and protrude from the logging tool so as to present a pair of main arm free ends (29, 31) that are spaced from an outer surface of the tool and are engageable with a borehole surface. The logging tool (10) or element (19) includes a mechanism for effecting coordinated, powered, linked movement of the main stabilizer arms (23, 24) between the retracted and advanced positions.