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Sonic processing (PDF)

Sonic processing

Data import
Borehole full wave sonic data from various manufactures are supported.
Data available in SEG-Y, 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 add-ons 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).