Seismic Stratigraphic Analysis of the North Apsheron Trend

Abstract

Dr Arzu Javadova

The Caspian Basin”s structural settings are – compared to the Southern Caspian Basin – less complex. Except for the Apsharon trend, which is a prominent overall anticlinal structure with an eastward dip of its axis, the area of investigation comprises a major northwest-southeast trending syncline and thus exhibits very limited structural potential. Structural closures are limited to the Pre-Cretaceous levels only which so far have not been tested by wells in the offshore. The Cretaceous forms anticlinal structures along the Apsharon trend. These structures appear open up-dip to the northwest with a potential culmination in the shallow water area not covered by the seismic data available. Wells on the Apsharon trend reaching the Cretaceous did not encounter a reservoir so far.

The better potential is supposed to be related to stratigraphic traps. Overall three plays are defined based on the seismic stratigraphic analysis:

Cretaceous reef play: Within the Cretaceous, there are good indications for buildups along a trend close to the Turkmenistan border. The definition of structural closures along the trend or potential up-dip pinch-outs along the trend requires further investigations [reprocessing] and a denser seismic grid to outline.

Pontian highstand delta: The Pontian highstand delta identified in the centre of the study area is interpreted from the progradation reflection pattern and can be reasonably well delineated as a progradational body with some slumping of distinct lateral extend. The Pontian Unconformity in the area east of the incised Paleo-Volga river and north of the delta is characterized by high amplitude becoming weaker again to the N. This area can be referred to as the delta plain area on the Pontian shelf with a high probability of reservoir-quality sands.

Productive Series Onlap/Pinch-out Play: With rising lake level in the South Caspian Basin the Central Caspian Basin was continuously flooded and the pre-existing relief [incised valleys, synclinal trough] became again an area of sedimentation. The relevant formations show northward onlap pinch-outs, the Pereryva pinch-out as the probably most promising reservoir was mapped in detail. The onlap positions of the higher Productive Series as well may represent further exploration potential, a detailed review of these pinch-outs.

PDF