[OpendTect_Users] Sweetness Attribute

Sat Jan 25 07:20:22 CET 2014

Is there an online resource discussing the pitfalls if sweetness 1 and 2?—
Jack

On Sat, Jan 25, 2014 at 12:57 PM, friso.brouwer <friso.brouwer at dgbes.com>
wrote:

> Rene,
> The sweetness attribute is a plain and simple tool to highlight 1) thick
> clean reservoir, and/or 2) hydrocarbons (HC) filled reservoir.
> Principle is you divide a amplitude attribute with a frequency attribute.
> For reservoir (low AI sand embedded in shale) the effects are that when the
> reservoir gets cleaner or thicker, the amplitude term increases due to
> higher reflectivity and frequency of the combined reflections lower as the
> thicknesses increases.
> For HC presence (assuming an AVO 3 environment, where introduction of HC
> leads to brightening), the effects are when HC gets introduced that
> amplitude increases due to higher reflectivity and frequency of the
> reflection is lower due to the combined effects of HC on the frequency
> content.
> From the mathematical formulation you see that all these effects work in
> the same direction. Of course it is also a very simple attribute and there
> are lots of pit-falls, which I will not list here, as it is a bit besides
> your question.
> The inst. amp / sqrt(inst. freq) is the original definition of this
> attribute, but it is easy to understand you can stick different terms in
> the equation for the amplitude related numerator and frequency related
> denominator and stay true to the underlying concept. The results will be
> strongly related, but not equal. I often use the instantaneous amplitude in
> the numerator as it removes the question what the best time gate, but I do
> not like to use the instantaneous frequency as it is sensitive to thin beds
> (which is, by the way, the basis of Tury Tanner's thin bed attribute).
> Putting a square root operator in the denominator compresses its original
> dynamic range and limits the effect of the higher frequencies.
> The nice thing of the attribute is that you can do other things as well,
> which are all quite easily implemented using OpendTect's mathematics
> attribute and other attributes:
> * Using energy instead of rms or inst. ampl in the numerator, which expands
> the dynamic range of the amplitudes and focuses the results on the very
> high amplitudes only.
> * Replace the amplitude term with a far stack amplitude or an AVO attribute.
> * Shift the frequency range, such that, with the original range going from
> Fmin to Fmax, the shifted range goes from c to Fmax-Fmin+c (with 0< c <<
> Fmin), this will really boost the effect of low frequencies in the
> sweetness attribute response.
> * Shift the time gate of the frequency attribute, such that the frequencies
> are extracted below the evaluation point. This is very useful as most
> frequency effects due to HC are found below the reservoir reflection.
> So it is a really nice attribute to play with and optimize doing
> recognizance type evaluation of reservoir and HC presence, but be cautious
> in its interpretation, as there is a long list if pitfalls.
> I hope this helps you forward.
>>
>> ---------- Forwarded message ----------
>> From: René Grobe <grobe at geo-t.de>
>> Date: Fri, Jan 24, 2014 at 2:17 PM
>> Subject: [OpendTect_Users] Sweetness Attribute
>> To: users at opendtect.org
>>
>>
>> Hi All,
>>
>>
>>
>> as non-geophysicist I have a question about the definition of the
>> “Sweetness” attribute. In literature the sweetness attribute seems to be
>> usually mathematically defined as “Sweetness(1) = Instantaneous
>> Amplitude/Sqrt(Instantaneous Frequency)”. In the OpendTect Attributes
>> Matrix (https://opendtect.org/opendtect_attributes_matrix/) “Sweetness(2)
>> = RMS Energy/Average Frequency” or “RMS Amplitude/Average Frequency”. It is
>> clear that both definitions - Sweetness(1) and Sweetness(2) - generally
>> relate Amplitude to Frequency, but do they exactly produce the same result
>> or do they differ in any way? If so, how can one describe the difference
>> and its impact on interpreting the result?
>>
>>
>>
>> Thank you very much!
>>
>> Best regards,
>>
>> René
>>
>>
>>
>> _____________________________________________
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>>
>>
>> René Grobe, PhD.
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