--> --> Synthetic Seismic Forward Modelling of Fluvial Outcrops from the Ebro Basin, Spain

2018 AAPG International Conference and Exhibition

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Synthetic Seismic Forward Modelling of Fluvial Outcrops from the Ebro Basin, Spain

Abstract

When constructing reservoir models of fluvial reservoirs exploration and appraisal well data provide a good understanding of the vertical variability, but a poor understanding of the lateral variability of depositional facies and architecture. Well exposed fluvial reservoir outcrops of the Ebro basin have been used to generate 2D synthetic seismic data to allow comparison of the lateral variability of these fluvial deposits with 3D seismic data from the South Lokichar Basin in Kenya. The Ebro Basin in north east Spain is a foreland basin which formed during the Pyrenees mountain chain development in the Oligocene. Deposition in the northern part of the Ebro Basin was dominated by two fluvial systems, the Luna system to the west and Huesca system to the east, and sediment supply came from older foreland basins as well as the Pyrenean axial zone. The relatively small scale and high degree of exposure of the Luna and Huesca systems make them ideal for studying the variety of fluvial stratigraphic architectures as seen at outcrop. Changes in gross stratigraphic architecture both laterally and down dip in these fluvial reservoir systems allow them to be divided into proximal, medial and distal zones. A series of different outcrop scale schematic illustrations have been created at different outcrops throughout the proximal, medial and distal zones. Two dimensional models of p-wave velocity, s-wave velocity and density were produced from these schematic illustrations using rock properties taken from wireline log data from the South Lokichar Basin in Kenya. Outcrop scale synthetic seismic data were generated via convolution of the velocity and density sections with a synthetic Ricker wavelet. The peak frequency of the Ricker wavelet was varied from 20Hz, 35Hz and 60Hz to investigate the impact of seismic resolution on the detectability of different depositional elements across a range of scales on different outcrops. Synthetic seismic data were then compared with 3D seismic data from the South Lokichar Basin to support the interpretation of lateral variation within the Miocene fluvial reservoirs found in this basin.