Torsional wave logging

A system for torsional wave logging in a borehole of a subterranean formation, comprising:

• a sonic tool in the borehole comprising:
• a torsional wave transmitter configured to generate a torsional wave propagating within a cylindrical layered structure associated with the borehole, wherein the cylindrical layered structure comprises the subterranean formation and a completion of the borehole, wherein the torsional wave transmitter is mounted on a first sliding pad in the borehole;
• and
• a torsional wave receiver configured to obtain a torsional wave measurement of the borehole, wherein the torsional wave receiver is mounted on a second sliding pad in the borehole,
• wherein the first sliding pad and the second sliding pad are at a pre-determined distance from each other and are in frictional coupling with an inside surface of the completion.

A non-transitory computer readable medium storing instructions for torsional wave logging in a borehole of a subterranean formation, the instructions when executed causing a computer processor to:

• obtain a torsional wave measurement of the borehole, wherein the torsional wave measurement represents characteristics of a torsional wave propagating within a cylindrical layered structure associated with the borehole, wherein the cylindrical layered structure comprises the subterranean formation and a completion of the borehole;
• analyze the torsional wave measurement to generate a quality measure of the completion;
• and
• display the quality measure of the completion.