SUB-SALT SEISMIC IMAGE ENHANCEMENT USING 3D PRE-STACK DEPTH CONTROLLED BEAM MIGRATION -RASBUDRAN FIELD, CENTRAL PROVINCE OF THE GULF OF SUEZ, EGYPT

The geological nature of the Gulf of Suez has a complex geological setting that poses challenges
for seismic imaging.Geologically the Gulf of Suez contains the Upper Miocene - Zeit Formation with low velocity
shaley beds and high velocity of salt and anhydrite beds that causes a lot of multiples. In addition, the presence of
several tilted fault blocks results in big lateral change in velocity. The presence of high velocity layers like Miocene
salts and anhydrites within the sedimentary sequence in the Gulf of Suez enhances the reflection coefficient along their
interfaces with consequently apparent resolution of these horizons on seismic sections. As a result, the absence of any
beneficial seismic reflection horizons of any rock unit below this evaporite section is clearly observed. That is in turn,
leads to difficulty of imaging the pre-salt reflectors due to the significant lateral velocity variations, distortion of
raypaths and time pull-up created by salt. The present study discusses the depth seismic images of the deep structural
objectives beneath a complex overburden that may show strong horizontal and vertical velocity variations. In such
areas, the seismic image is frequently of poor quality and the depth model of deep layers is often false due to the
perturbed propagation of seismic energy through the deforming effect of the overlying layers. This complexity of the
geologic section makes seismic processing and interpretation being a big challenge for geophysicists. Hence, planning
and drilling new wells are so difficult due to unexpected events, i.e. faults, missing targets etc. Several
interpretations based on the 2D and 3D seismic were performed in the Ras Budran study area. Pre-stack time
migration (PSTM) seismic sections are strongly affected by multiple activities and heavy seismic energy loss due to the
problems mentioned above. Hence, 3D pre-stack depth migration with a controlled beam migration algorithm was used
to enhance the sub-salt seismic imaging at Ras Budran oil field, central province of the Gulf of Suez.