GEOPHYSICS LETTERS

Ghalib M. et. aL 55of the gulf itself, which is a huge graben with successive block faultingaway from its center and parallel to it (Said, 1962, Moustafa, 1993,Gobashy et ai, 2000, Jordi, 1984 and El Naggar, 1988).The aim of this study is concerned on the study of criteria, orgeophysical parameters by which we can recognize and interpret thecarbonate build-ups (reefs) by using seismic data, the Nullipore rock onRas Gharib, Shoab Gharib, and Ras Fanar oil fields Gulf of Suez ofEgypt is taken as example to the present study. The following subjectshave been studied to recognize and interpret the reefs by conjunctionbetween these subjects:1- Use of seismic parameters obtained from well log data such asvelocity, density and acoustic impedance to recognize the reefs onseismic sections, by tying these parameters to the seismic lines,and how these parameters are used to recognize the lithology.2- Interpretation according to criteria by which we can recognize thecarbonate build-ups (reefs) by using seismic data.3- Environmental study, mapping, and distribution of reefs.4- Depositional history of the carbonate build-ups (reefs) by seismicstudy.The criteria that can identify the reefs on seismic section dependprimarily on the difference in compaction between reefs and the adjacentstrata, and the presence of high velocity contrast between the reef andthe overlying rock, often a lot of higher, therefore there is a strongreflection at the top of the reef, but when the velocity of the reefs isnearer to the velocity of the overlying rocks ( especially in the presenceof gas at the top of the reef), then the reflection is weaker and the dimspot appear. In this case it is very hard to fined or identify the reefs onthe section.The following subjects have been studied to recognize and interpretthe reefs: /1- Density, velocity and acoustic impedance, as interpretingparameters and lithologic indicator: