Method and device for acoustic borehole measurement

摘要

A method and a device for generating acoustic waves and transmitting them into an underground soil formation for the purpose of measuring it comprises suspending a measuring probe in the borehole inside a formation which accommodates a generator for simultaneously generating a plurality of acoustic waves which extend in the direction of and at a uniform spacing from the longitudinal axis of the probe. An acoustic energy reflector inside the housing reflects the waves radially outwards from the axis into the formation at an angle which is essentially perpendicular to the axis. Detectors inside the housing, which have a longitudinal spacing from the generator and the reflector, record the acoustic energy from the formation which is yielded from the reflected waves. According to a preferred embodiment, the generator comprises four cylindrical magnetostrictively excited elements which are arranged about the central axis of the probe and of which each has an axis parallel to the central axis, so that the four axes of the elements form, seen in the direction of the central axis, the four corners of a square. The elements are designed such that in the event of an excitation a prescribed element vibrates out of phase in the longitudinal direction, relative to the two adjacent elements, the vibration of the four elements forming together two positive and two negative waves which interfere with one another when they are reflected into the formation ... Original abstract incomplete.