SOIL INVESTIGATION METHOD AND APPARATUS FOR APPLYING THIS PROCESS.

摘要

A multipole shear wave logging device includes a logging sonde (10), means (12) for generating a 2n-pole eg octopole shear wave in an earth formation (22) surrounding a borehole (20) containing liquid where n is an integer greater than 2, and means (D1, D2) for detecting in the liquid a refracted compressional wave produced by the 2n-pole shear wave. The detecting means comprises two detectors (D1, D2) in the liquid spaced apart longitudinally from each other and from the generating means (12). The shear wave velocity of the formation is determined from the time interval between detections of the refraction of the octopole shear wave by the two detectors (D1, D2). The octopole generator 12 comprises 6 circumferentially spaced piezoelectric segments which are operated so that opposed ones contract and expand in opposition. The detectors 14 may be of similar construction. IMAGE