Reflective response and velocity discrimination in the central part of the gulf of suez, Egypt

Abstract EN

This paper describes the effect of basin configuration on the thickness variations and reflectivities (reflection and transmission coefficients), as well as the role of lithologic heterogeneity on the velocities (interval and average) of some stratigraphic sequences in the central part of the Gulf of Suez, principally at the southern part of Belayiin Oil Field.

The high velocity values may be attributed to the occurrence of massive non clastics (evaporites) and the low velocity ones due to loose clastics (shale).

Isopach, reflectivity and velocity maps for four formations (Zeit, South Gharib, Belayim, and Kareem) are constructed, which reflect the behavior of depositional conditions, and the tectonism standing behind the sedimentation.

The reflection coefficient values are generally positive at the tops of Zeit and South Gharib Formations, except at GS 278-1 well, that is the velocity increases downwardly and in the NE-SW direction.

On the other hand, the negative values of the reflection coefficient increase at the tops of Belayim and Kareem Formations, i.e., the velocity decreases downwardly.

This area is subdivided into six depositional basins trending in the NW-direction.

The velocity anomalies appeared to be structurally controlled and are caused by the sound waves going through the salts, reefs, igneous dikes, and distorted beds.

It is possible to identify the sources of these anomalies and allow to predict the distortion of the recognized reflectors.

In some cases, the velocity data are complete enough to establish a corrected section.

The velocity discrimination in the Gulf of Suez is dealt with; it is considered the key to the seismic re-processing in this complex structural area.

The stacking velocities at their best prediction cannot be expected to be equal to the check-shot velocities, unless proper attention is paid to the velocity corrections and to the exact position of the wave pulse selected for picking.

All these maps are constructed in order to deduce the acoustic parameters of the different environmental conditions.

The processing steps in the central part are completely different from the coastal zones.

The Miocene salt causes not only structural deformation in the post-salt sections, but also severe time distortion of the presalt reflections.

Comparison of the event on stacked and migrated sections through the salt diapir made it obvious that the time migration was inadequate and a depth migration process was required.