SIMULATING PRE AND POST STACK MIGRATION FOR 2D SEISMIC LINE IN BALAD-SAMARRA AREA, CENTRAL IRAQ: A SEISMIC UNIX IMPLEMENTATION

Abstract

Migration is a process by which reflectors are re-positioned to their true subsurface locations. The accuracy of the migrated velocity model and time determines the subsurface imaging quality. For complex structures, the reflecting and/or diffracting energy from source points will not vertically be oriented beneath the common mid-point (CMP). However, an acceptable migrated velocity model is usually performed by several parameters. Stolt migration method is applied to a 2D seismic line within Salah Al-Din province (Balad-Samarra area), central Iraq. To understand the effect of Stolt migration method and parameters used in the migration, a simulated synthetic model has been made with the same field parameters for the studied seismic line and with the same vertical cross-section of the geological subsurface layers. This model is constructed to generate raw seismic data, which was reprocessed using Seismic UNIX (SU) package in the post and pre-stack migration situation. Stolt migration is applied in the time domain for the modeled processed data to test the effects of changing the values of each parameter. A suitable migrated velocity values deduced from the analyzed model is tested for real surveyed line and the images results for the subsurface structures are accurate without diffraction. The results indicate that pre-stack time migration is best due to the lateral velocity variation and structural complexity and velocity analysis confirm that prestack is better than post-stack time migration.