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Phase and Polarity Checking

PHASE/POLARITY CHECKING

Phase and polarity checking is done due to few important reasons:

To recognize high-amplitude reflections and to understand their geologic cause
Reflections are generated by Acoustic Impedance (AI) contrasts, thus high amplitude reflections, results in high AI contrasts.
Important to understand whether the reflection package studied is caused by single interface or by a layer with interfaces top and base.

1.PHASE

There are three type of phase:

1.Minimum Phase

The wavelet has a short time duration and a concentration of energy at the start of the wavelet. It is zero before time zero (casual). The wavelet is coincide with the exact position of the subsurface interface

2.Maximum Phase

The time reverse of the minimum phase and at every point the phase is greater for the maximum than the minimum.

3.Zero Phase

The wavelet is shorter duration that the minimum phase equivalent. The wavelet is symmetrical with a maximum at time zero (anti-casual). Usually preferred during processing, hence interpretation to eliminate time delay. Max amplitude of the wavelet is coinciding with the lithological interface.

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2.POLARITY

American polarity means increase in impedance is a blue reflection.
European polarity means increase in impedance is a red reflection.

Figure 1: Minimum Phase

Figure 2: Maximum Phase

Figure 3: Zero Phase

Figure 5: difference between American and European Polarity

Figure 6: Cross Section data from our project

from data given, Figure 6 show example of American polarity. from the soft to hard body the amplitude is positive (red). while if the amplitude is negative (blue), it showed that it is European polarity.