Essential Aspects in Seismic Reprocessing 2D Legacy. Case Study: Ucayali Basin, Peru

Abstract

In 2017 CEPSA re-processed 1,000 Km of 2D seismic in one exploration block in the Ucayali basin. Most of the 80% of the data were recorded in the 70s and they are characterized by their low fold. The main objective of the project was the uplift of the structural imaging compared to previous versions. Preparation of the support data was a key stage during the re-processing. Due to the characteristics of the data, it was necessary the application of techniques for the reconstruction of the planimetry, altimetry and geometry of sources and receivers. Digital models were used for the assignment of elevations. Furthermore, a revision of the migration of the river basin in comparison to the intersection of the 2D lines from 1970 until 2017 was carried out. The re-processing demonstrated that specific workflows were needed for the attenuation of different types of noise paying special attention to the preservation of the signal at the lowest frequency. Robust models of weathering and sub-weathering were required for static correction and migration tests. Horizon-guided velocity analysis, the application of residual statics and variation of velocity of 2-3% led to the uplift of the migrated data. Ray tracing was used to model the effects of the statics and for the analysis of possible artifacts. The lessons learned in this project will be the reference for future processing projects in the Ucayali basin.