Application of the wavefield illumination method in a subthrust model in the Upper Magdalena Basin (Colombia)

Patricia Chajín,Germán Camacho,Edwar Herrera

doi:10.18273/revbol.v43n1-2021008

Abstract

Complex structures like subthrust show high risk during the definition of structural traps in low quality seismic images in depth, so we can use the structural interpretation to simulate the subthrust illumination by wavefield of a prospect area in order to reduce the uncertainty and support the oil exploration process. In general, we performed an exercise of 2D geophysical modeling using a wavefield illumination simulator. At first, we interpreted two geological models from a seismic line in depth. The geological interpretation was adjusted with information about structural styles in this part of Upper Magdalena Basin. Then, we use a velocity scenario and assign these velocities to both geological models. The wavefield illumination method allows us to see all of the wavepaths in the different pair of source-receivers in order to do a fast evaluation of the structure illumination. This could be used to improve the seismic acquisitions in structurally complex media.

Highlights

The study area is located in Upper Magdalena Basin, Colombia (Figure 1); in the Neiva Sub-Basin.The last years Neiva Sub-Basin have been underexplored, because the most prospective areas are associated with subthrust structures and the majority of drilled wells have been unsuccessful (De Freitas, 2000)
The geology and stratigraphy of the Neiva Sub-Basin have been described in several works (Carrera-Ortiz, 2015; Jiménez-Díaz, 2008; Mojica and Franco, 1990) but due to lack of high quality in 2D seismic images and new exploration concepts (De Freitas, 2000; Macellari et al, 2003), little attention has been paid to the subthrust structures, principally in the possible prospective zones beneath Chusma, San Francisco and Upar faults
The main target of this work is to try a 2D geophysical modelling applying wavefield illumination method, from two different seismic interpretations associated to one velocity scenario built from wells and seismic velocities (Macellari et al, 2003; Duarte et al, 2019) in a two stages methodology; in order to evaluate if the illumination could be improved for this section even in the zones under Chusma and Upar faults

Summary

Introduction

The last years Neiva Sub-Basin have been underexplored, because the most prospective areas are associated with subthrust structures and the majority of drilled wells have been unsuccessful (De Freitas, 2000). The geology and stratigraphy of the Neiva Sub-Basin have been described in several works (Carrera-Ortiz, 2015; Jiménez-Díaz, 2008; Mojica and Franco, 1990) but due to lack of high quality in 2D seismic images and new exploration concepts (De Freitas, 2000; Macellari et al, 2003), little attention has been paid to the subthrust structures, principally in the possible prospective zones beneath Chusma, San Francisco and Upar faults. The main target of this work is to try a 2D geophysical modelling applying wavefield illumination method, from two different seismic interpretations associated to one velocity scenario built from wells and seismic velocities (Macellari et al, 2003; Duarte et al, 2019) in a two stages methodology; in order to evaluate if the illumination could be improved for this section even in the zones under Chusma and Upar faults

Methods

Results

Discussion

Conclusion