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Abstract: Searching for Stratigraphic Traps In the Neuquen Basin of Argentina

J. P. Blangy, M. Follis, G. Tavella, C. Wright

Amoco Argentina Oil Company secured a farm-in from YPF (50-50 partnership) over the blocks CN-VIII and ON-IX in the Neuquen basin of Argentina. Primary reservoir horizons are Late Jurassic and Early Cretaceous eolian sands. The petrophysical properties of these dunal sands contrast--sometimes sharply--with those of the silts and shales of similar age in the immediate area. Initial evaluation of the blocks had recognized stratigraphic potential associated with the dunal facies, especially in the CN-VIII block. The presence of reservoir quality Avile sands (Barremian age, 18-20% porosity) was mapped on the CN-VIII block directly from older vintage seismic.

1. Seismic Acquisition: Amoco shot approximately 400 km of high resolution 120-fold seismic in late 1994 to high-grade those leads identified on the old seismic. The CN-VIII block is partially covered by basalts of varying thickness. The new data was shot over areas where the basalt is relatively thin (limited to 150 m or less) with large vibrators and offsets of up to 3000 m. The Amoco survey resulted in an improved penetration through the basalts; it also had a much higher frequency content and yielded superior bed resolution than any previous survey in the area.

2. Seismic Processing and Modeling: Amoco reprocessed in-house several key lines over producing fields in the immediate area and approximately 200 km of seismic from the 1994 survey in the CN-VIII block for detailed amplitude analysis. Seismic amplitude models [including (1) 2-D stratigraphic pinchout models describing the presence of porous sand lenses, and (2) AVO models] tie the 1994 data very well.

3. Integrated Seismic Interpretation and Reduction of Technical RISK: The integration of various disciplines (Petrophysics, Geophysics, Geology, and Engineering) resulted in the calibration/ranking of seismic responses observed over the CN-VIII area, thus substantially reducing the RISK on trap definition, reservoir quality, seal, and product associated with the early leads. The Matansilla-1 wildcat targeted a high-graded anomaly and resulted in a gas discovery. It will be delineated in 1996 via 3-D seismic data and additional drilling.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela