DualFrequencyPanels™ processing technique is required for FloatSeis UltraDeepImaging™ surveys’ data processing. It has to deal with two major challenges: to deblend the overlapped data emitted by different sources and to stack high frequency and low frequency datasets.
Dual Frequency Deblending. FloatSeis UltraDeepImaging™ survey design assumes simultaneous shooting by a standard source and a Low Frequency source. This is done to increase production rate of the survey, reduce costs and make FloatSeis UltraDeepImaging™ surveys affordable without loss of total depth and quality of the data. But the problem is that towed streamer records all the data which is “available” at the particular moment, thus valuable seismic reflections and refractions can be overlapped by each other. As a result, reflections excited by a standard source will be disguised by reflections and refractions emitted by a Low Frequency source and vice versa.
An example of blended shot acquired during FloatSeis UltraDeepImaging™ survey (simultaneous shooting by standard and Low Frequency sources installed on different source vessels). Valuable standard source seismic data disguised by Low Frequency energy is on the left part of the record. Valuable Low Frequency source seismic data disguised by standard source energy is on the right part of the record. Overlapping of these datasets is a challenge for a DualFrequencyPanels™ processing technique.
The aim of the deblending procedures is to retrieve data as if it was acquired in the conventional way, without simultaneous shooting and consequent overlapping, because after deblending the conventional and standard way of processing can be applied in practice.
Tau-p transformation is used to deblend overlapped data. The Tau-p transformation is another special case of RADON transformation where the data are decomposed as a series of straight lines which map to points in the Tau-p domain. Hyperbolic events map to elliptical curves in Tau-p. This process also used to be referred to as slant-stacking. Tau-p transformation performs well with the FloatSeis UltraDeepImaging™ survey shooting geometry because of waves emitted by different sources have distinct slants. This helps to deblend seismic record without loss of any valuable data.
An example of deblending procedure results. Dual Source Gather contains both records of the standard source and Low Frequency source energy (on the left), thus valuable data is overlapped one by another. Standard source gather after deblending is represented in the center. All Low Frequency source energy was eliminated from the standard source gather. While Low Frequency source gather after deblending is on the right panel.
Dual Frequency Stacking. To obtain superior deep reflected CDP data standard source gather and Low Frequency gather have to be stacked together. Standard source gathers’ stack has a better resolution in the upper part of the seismic section because of the higher frequency spectra but a relatively low depth of investigation whereas, in contrast, Low Frequency gathers’ stack has lower resolution in the upper part of the seismic section but it reveals deep depth horizons and structures because of better penetration properties of low frequency energy. Merging two datasets gives us a final seismic section that inherits essential features of both standard and Low Frequency stacks.
Comparison between standard source, Low Frequency source and the merged final stacks. Standard source stack differs by better resolution in the upper part of the seismic section; Low Frequency stack outstands with better deep depth horizons imaging and merged final stack, as a result of DualFrequencyPanels™ processing technique, combines advantages of both standard source and Low Frequency source stacks.
Dual Source Gather
Standard Source Gather after deblending
Low Frequency Source Gather after deblending
Standard source stack
Low Frequency stack
Merged final stack