Seismic subsurface structure study to determine the actual depth of the Cretaceous succession

Abstract

In this study, the technique of seismic attribute was applied on two-dimensional seismic sections in order to generate accurate depth map of Nhr-Umr Formation and to reveal the fault trend in Luhais oil field, southern Iraq. The Nhr-Umr Horizon was tracked depend on the check shot which is available only in two wells (Lu 2 and Lu 21).The importance of Nhr-Umr Formation is considered as the main reservoir of oil in this field . The time map of Nhr-Umr Horizon shows that there is a major irregular enclosure including above many minor enclosures. The depth conversion process was carried out by using different velocity models. The accurate model that gives less differences between the actual and estimated depth have been created to convert the time map into depth map. The depth map of Nhr-Umr Formation is more dense than the time map and shows irregular shape. The depth increase toward the northeastern part of the area reached to depth of 2550 m. whereas the depth is reduced in the crest of the structure reached to 2400 m. The differences between the time map and the depth map because of the horizontal variations of velocity in the field. The main trend of faults in this field is north-south