Abstract: A method and apparatus of detecting fractures along the wall of a formation, such as a well formed by test-drilling, provides for the transmission of ultrasonic signals in a direction essentially perpendicular to the wall from a position spaced from the wall by a predetermined distance and the reception of the ultrasonic signals which may be reflected by the wall. The space of predetermined thickness between the transducer which generates the ultrasonic signals and the wall is filled with an intermediate material which does not form a distinct interface with the wall of the type which would be able to produce an appreciable parasitic reflection of the transmitted signals.

Abstract: Acoustic signals are transmitted in a direction substantially perpendicular to the borehole axis, from different levels of at least three determined generatrices of the borehole wall. Reflected acoustic signals are received from the same direction at different levels of these generatrices. A train of signals is derived from each reflected acoustic signal and at least a group of significant elements of this signal train is selected. The groups of significant elements of the signals obtained for the different generatrices are correlated. The interval between signal trains corresponding to the maximum correlation corresponds to one and the same geological formation and is representative of the dip angle of this formation.

Abstract: The device, which is connected to an element to be displaced, comprises a tubular body surrounded by sleeves which are inflated to a diameter slightly smaller than the diameter of the conduit. A motor-pump assembly located in the tubular body provides for the circulation of the fluid through the body so as to cause propulsion of the device within the conduit. Sensors may control automatic operation of the device and inflation of the sleeves to the selected diameter.

Abstract: The sonde comprises a measuring wheel carried by an arm which holds it in contact with the borehole wall and rotates it around the sonde axis so that the measuring wheel follows a helical path on the borehole wall as the sonde is raised in the borehole.