Processing of large offset data: experimental seismic line from Tenerife Field, Colombia

Francisco Gamboa Ortega,Michelângelo Gomes Da Silva,Ellen De Nazaré Souza Gomes,Andrei Gomes De Oliveira,Amin Bassrei

doi:10.1590/2317-4889201820170072

Abstract

ABSTRACT: Exploration seismology provides the main source of information about the Earth’s subsurface, which in many cases can be presented as a simple model of horizontal or near-horizontal layers. After the seismic acquisition step, conventional seismic processing of reflection data provides an image of the subsurface by using information about the reflections of these layers. The traveltime from a source to different receivers is adjusted using a hyperbolic function. This expression is used in the case involving an isotropic medium, which is a simplification of nature, whereas geologically complex media are generally anisotropic. A subsurface model that more closely resembles reality is the vertical transverse isotropy, which defines two parameters that are required to correct the traveltimes: the NMO velocity and the anellipticity parameter. In this paper, we reviewed the literature and methodology for velocity analysis of seismic data acquired from anisotropic media. A model with horizontal layers and anisotropic behavior was developed and evaluated. The anisotropic velocity was compared to the isotropic velocity, and the results were analyzed. Finally, the methodology was applied to real seismic data, i.e. an experimental landline from Tenerife Field, Colombia. The results show the importance of the anellipticity parameter in models with anisotropic layers.

Highlights

The main objective of exploration seismology is to obtain subsurface images that may indicate possible hydrocarbon reservoirs after proper interpretation
In the seismic interpretation step, the images obtained from seismic reflection data should be faithful to subsurface characteristics
One factor that contributes to this difficulty is the type of processing performed on data

Summary

INTRODUCTION

The main objective of exploration seismology is to obtain subsurface images that may indicate possible hydrocarbon reservoirs after proper interpretation. In the seismic interpretation step, the images obtained from seismic reflection data should be faithful to subsurface characteristics. The normal moveout (NMO) velocity is not equal to the root mean square (RMS) velocity, both for small and large offsets. This type of medium produces a non-hyperbolic traveltime curve, which is manifested by significantly large offsets for PP-waves, i.e. a P-wave reflected as a P-wave. The mathematical representation of the source-reflector-receiver traveltime can be expressed by a shifted hyperbola (Castle 1994).

Seismic processing of large offset data

SIMULATIONS WITH SYNTHETIC DATA

Vnmo forv the

APPLICATION TO REAL DATA

Findings

NMO correction with