Sonic log data provides us with the speed of elastic waves in the rock around the borehole – but not directly. Extracting wave speeds is a complex procedure, which to a large extent relies on interpretation.
An operating company may wish to verify data that was previously processed, or reprocess a log with a specific purpose in mind, for example to extract mechanical properties.
Eriksfiord carries out quality control, data analysis and processing of sonic logs, and calculates mechanical rock properties from density and sonic information.
Of particular interest is the shear wave speed which can be measured either from a non-directional (monopole) source, or inferred from the flexural wave from a directional (dipole) source.
The shear wave will be polarized in an anisotropic rock, which enables us to extract both the speed and the direction of the shear wave. Under certain favourable circumstances, we can gain information about micro-fracturing, rock texture and rock stress.
Dipole processing can give misleading results when not performed correctly. Conversely, interesting information may remain hidden in the data. Eriksfiord therefore performs a thorough and independent quality control, and provides an extensive documentation of the processing.