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Geology _ Geophysics in Oil Exploration

Usually this data came in seismic section papers not

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Unformatted text preview: sented by short wavelets. Because spike passes through earth layers which act as a filter & applies an operator to Spike & transform it into short wavelets, applying this operator known as Convolution. The process used to return short wavelets to spikes known as Deconvolution. Muting Editing Types of Deconvolution: 1. DBS & DAS • DBS: is Deconvolution before stack (standard process applied to all data) DBS removes any short multiples & reverberations (relatively short 200-400ms) • DAS: is Deconvolution after stack (mainly used in marine data) DAS removes long period multiple 2. Spike Deconvolution & Predictive Deconvolution • Spike Deconvolution: used for sources as air gun & Dynamite (used before stack). • Predictive Deconvolution: used for sources as Weight drops (which doesn’t generate many high frequencies) 3. Minimum phase & Zero phase • Minimum phase Deconvolution: whiteness spectrum & correct the phase lags (shift the data). • Zero Phase Deconvolution: just whiteness spectrum without any shift of data. 39 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration Filtering: A process or algorithm using a set of limits used to eliminate unwanted portions of seismic data, commonly on the basis of frequency or amplitude, to enhance the signal-to-noise ratio of the data or to achieve Deconvolution. The common use of digital filter in data processing is to filter out unwanted frequencies. Types of filters: • Band-Pass filter: This filter doesn’t alter phase, only extract a defined band of frequencies Any high or low frequencies outside this range will be attenuated. • Low-Cut filter (High pass): In this case, the analysts only want to eliminate low frequencies Low-cut filter is used to filter out low frequency Ground Roll. • High-Cut filter (Low-Pass): In this case, the analysts only want to eliminate high frequencies • Notch filter: It is used to filter out narrow band of frequencies within frequency range of data The most common use of this filter is to attenuate noises caused by power lines. • Variable amplitude spectrum filter: In this case, the analyst...
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