Resolving Deep-Water Channel Architectures: High-Resolution Forward Seismic Modeling of Turbidite Systems, Ainsa II Channel, Campodarbe Group, Northern Spain

Abstract

Turbidite channel systems are a common target in exploring for petroleum reservoirs though their internal architectures can be highly varied. To investigate channel architectures in turbidite systems, the spectacularly exposed, Ainsa II channel in the Spanish Pyrenees is used to generate forward synthetic seismic 2D sections. Three parameters are varied independently: input model detail, seismic impedance contrast, and dominant wavelet frequency. Representative seismic velocity and rock density values are taken from published reservoir data for observed lithologies. The three petroleum reservoir scenarios investigated are: a Plio-Pleistocene Gulf of Mexico reservoir and Tertiary and Jurassic UK North Sea reservoirs. Four Ricker wavelet dominant frequencies are chosen to generate the seismic models: 26, 52, 78 and 104 Hz. Results show that 2D synthetic seismic images generated from the low frequency wavelets (26 Hz) do not resolve the important heterogeneities within the channel complex. At 52 Hz, frequencies that are typically used for the interpretation of shallow-level, Tertiary targets, an improved seismic resolution of the input model can be achieved, suggesting that the target interval consists of stacked channels, although not all channel units are resolved. At 78 Hz, which is typical of high-frequency seismic acquisition and processing, an interpretation close to the input geological model can be achieved. At 104 Hz, the excellent seismic resolution can be interpreted to reproduce the input model. The results also show that differing impedance contrast values have little effect on the geological interpretation at the high signal/noise ratios used, although impedance values from the UK North Sea Jurassic reservoir analog yield the highest amplitudes in the synthetic sections.