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# Geophysics/Defining SEG Polarity together with American and European Convention

Question
Dear Farrukh,

Appreciate if you can help to solve my confusion.

You have stated that the SEG conventions can be classified as SEG-Normal and SEG-Reverse. For a normal case of SEG-Normal, if the convention of the seismic is Europen, the positive impedance would be displayed as a trough.

IF, it is stated that the polarity of the seismic is SEG-Reverse, whenever if there is increase of the acoustic impedance, is it consider as European Convention as well?

Dear Nabila,

This is always confusing and I wonder if you are stating it from my earlier answers or is this your own perception.

The difference between the SEG and EU is -1. If SEG says +1 then EU says -1 for the same thing.

Let us assume that we use a zero-phase data such that the zero-phase is our bed boundary. The bed boundary on an impedance is defined such that you have either a sharp increase or a sharp decrease in impedance trend. Then,

SEG Conventions

Increase in impedance is represented as a positive amplitude if you use SEG-Normal convention.

Decrease in impedance is represented as a negative amplitude if you use SEG-Reverse   convention.

EU Conventions

Now you can translate this into EU conventions by changing the sign of the amplitude.

Increase in impedance is represented as a negative amplitude if you use EU (hard-kick) convention.

Decrease in impedance is represented as a positive amplitude if you use EU (soft-kick) convention.

In conclusions, these words are confusing. Neither use the hard/soft words nor use SEG/EU term if you want to be a neutral. Always write/say such that you express increase in impedance is represented as a positive amplitude or a negative amplitude . Then you are there.

P.S: This is an interesting blog!

http://www.agilegeoscience.com/journal/2012/4/5/polarity-cartoons.html

http://subsurfwiki.org/wiki/Polarity

Cheers, Farrukh
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Geophysics

Volunteer

#### Farrukh Qayyum

##### Expertise

I would like to answer Geophysical questions with keen interest, specifically exploration related. I want to hear from users for their queries on exploration geophysics/geology. Especially in the discipline of Reservoir Characterization from seismic reflection data. The questions related to basics and interpretational applications would be most welcome. I can also answer queries related to sequence and/or seismic stratigraphy, geology, general geomorphology, seismic geomorphology and other relevant questions. I can not answer the questions related to gravity, magnetic, or resistivity surveying or question related to the fluid dynamics. Such categories are not related to my experience.

##### Experience

Over eight years in different services with additional case studies of Pakistan, China, Saudi Arabia, North Sea, Africa and Netherlands offshore.

Organizations
dGB Earth Sciences, The Netherlands.

Publications

4D Wheeler Diagrams: Concept and Applications, Qayyum, F., P. de Groot, N. Hemstra, and O. Catuneanu, 2014, Geological Society, London, Special Publications, v. 404, p. SP404.1, doi:10.1144/SP404.1.

A Modern Approach to Build 3D Sequence Stratigraphic Framework Qayyum, F., Hemstra, N., and Singh, R., 2013, Oil and Gas Journal, vol.111, issue 10.

Dense sets of seismic horizons - A New Approach to Stratigraphic Interpretation Qayyum, F., Hemstra, N., and de Groot, P., 2013, Geophysical Corner, AAPG Explorer, September Issue, 68-69.

Developments and Future Trends in Wheeler Diagrams Qayyum, F., Catuneanu, O., de Groot, P., 2013, 75th EAGE Conference & Exhibition incorporating SPE EUROPEC, London, UK, June 2013.

HorizonCube and Wheeler Transform Generated, Stratal Packages Identified and Correlated on 7 Regional 2D Seismic Lines McDonough, K.J., Qayyum, F., Bouanga, E., and Pierard, C., Horn, B., Gross, J., Danforth, A., Sterne, E.J., Granath, J., AAPG Annual Convention & Exhibition, May 2013

On the horizon, de Groot, P., Qayyum, F., Oilfield Technology, January 2013.

Attributes play important role in seismic interpretation, de Groot, P., Qayyum, F., Hart's E&P Magazine, p. 31-34, October 2012.

From 2D to 4D Wheeler Diagrams, F. Qayyum, P. de Groot, and N. Hemstra, William Smith Meeting 2012, London.

Building a Sequence Stratigraphic Framework from HorizonCube and Well Data F. Qayyum, P. de Groot, J. Yasin 74th EAGE Conference & Exhibition, 2012

An old favourite, F. Qayyum and P. de Groot, Oilfield Technology, March 2012.

Using 3D Wheeler diagrams in seismic interpretation – the HorizonCube method F. Qayyum, P. de Groot,N. Hemstra First Break 30 (3), 103-109,2012

Education/Credentials
Master in Philosophy with specialization in reservoir characterization by using Sequence Stratigraphy. And master in Geophysics with a case study of Punjab Platform.

Awards and Honors