Sonic processing (PDF)
Data import
Borehole full wave sonic data from various manufactures are supported.
Data available in SEGY, SEG2 format and Mala borehole radar data
are also supported.
For data available in LIS/DLIS format files, you will have to
use the LIS/DLIS addons module.
Data preprocessing
A range of preprocessing techniques are provided to get optimize
data prior to applying the relevant process.
Filtering can be applied using moving average, weighted average
or frequency. For improved results, these filters can be combined.
In some cases, it might be useful to interpolate bad traces prior
to filtering.
Cement bond Evaluation
The cement bond evaluation can be done using either the Standard
gate method or the E1 based method.
DT Picking
WellCAD allows different algorithms for dt pick up. The standard
threshold algorithm returns the transit time at the first amplitude
value greater or equal to the specified threshold value, found
after the blanking window.
The advanced threshold process computes the ratio of the average
value of signal and noise windows. The user may define the values
for blanking, small window width, and large window width and ratio
threshold.
Velocity analysis
The velocity analysis can be done using the semblance method or
adjust extremum method
mechanical properties computation
Sonic logs are widely used to provide formation porosity/permeability
and mechanical properties. If dt compressional, dt shear and Rhob
are known, WellCAD may computes for each depth mechanical properties
of the rocks: Poisson ratio, shear Modulus, Young’s modulus,
Bulk modulus, Bulk Compressibility.
Reflected Tuve wave analysis
The tube wave may be seen as indicator of fracture. Prior to computation,
the offset, blanking, transmitter frequency and the fluid velocity
have to be defined. The process returns a well log. The value
of each depth is the cumulative energy computed over a V shaped
area in the late time area of the FWS log. The higher amplitude
could be seen as indicator of fracture (fluid velocity defining
the slope and the transmitter frequency the width).
