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Am bit confusing with following terms, please clarify.
1. Lithology stacks,fluid stacks,Ortho stacks
2. Chi angle vs Phi angle
3. how to find out optimum chi angle and phi angles?

Hi Krishna,

1. A lithology stack is a stack based on theoretical knowledge. For instance, on an AVO plot, you can draw a background trend representing a lithology and call it a lithological trend. You can use such a trend to make a new stack and call it a lithological stack. Fluid stack is a trend identified on a certain chart (mostly AVO/ AI based correlated with well data) that shows fluid behavior mainly. Any stack that is perpendicular to a given stack can be referred as orthogonal stack. I do not know much on this last one but this is an unconventional term to my knowledge.

2- Chi angle is a theoratical angle based on an actual phi angle. It is an approximation to Shuey's equation. Say Sin (A +/- B) is your eq. A is phi, which is normally an incident angle, and B is your chi, which is meant for quadrant rotation. You do Chi angle prediction to derive elastic impedance and/or rock properties.

3- Crossplotting is an easy approach. See the above link.


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Farrukh Qayyum


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.


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

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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

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

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