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Houston Geological Society Bulletin

Abstract


Houston Geological Society Bulletin, Volume 50, No. 07, March 2008. Page 12 - 12.

Abstract: Caspian Night. Vertical and Lateral Distribution and Continuity of the Balakhany VIII Formation of Azeri Field, Offshore Azerbaijan

Eldar Baghirov, Don Van Nieuwenhuise (speaker), Janok Bhattacharya, John Castagna and Jeffrey Yarus

The Azeri Field forms part of the ACG (Azeri, Chirag, Gunashli) megastructure, which is located 75 miles (120 km) offshore Azerbaijan. The reservoirs are multilayered sandstones forming traps within a major anticlinal structure. Proven crude oil reserves are estimated to be 5.4 billion barrels of oil.

In this study, fluvial/fluvio-deltaic reservoir sandstones have been correlated using more than 40 wells, approximately 1525 ft (465 m) of core from three wells, seismic data and outcrop analogs. Even though previous lithofacies descriptions and basic interpretations of the Balakhany VIII formation are sound, the stratigraphic interpretation of this interval is considerably improved through the utilization of several quantitative and semi-quantitative methods. There are several methods for estimating the geometry of channel belts: measurement of outcrop analogs, well-to-well correlation, empirical equations (involving maximum channel depth and channel belt width) and amplitude analysis of 3D seismic data.

Outcrop analogs show that the width of the channel belts ranged from 2000 to 3300 ft (600 to 1000 m). Core data was used to estimate the maximum and mean channel thickness, which appears to be within 15–24 ft (5–7 m) and 8–11 ft (2.5–3.5 m) in TST (true stratigraphic thickness), respectively. Applying empirical equations from Bridge and Mackey (1993), channel belt widths were predicted to be 690–3500 ft (210–1067 m). 3D seismic volumes were provided to perform seismic interpretation and construct appropriate maps, which allowed the analysis of interpreted horizons to clarify the width of channel belts directly. The widths of these channel belts are 2000–3300 feet (600–1000 m), the same range as seen in outcrop analogs.

Once the dimensions of the channel belts were established and correlation was completed, 2D models of the Balakhany VIII Formation were constructed.Wells were proportionally spaced in these models and, using the dimensions of channel belts previously obtained from analogs, the channel belts were interpolated between wells. This provides a more complete interpretation of the Balakhany VIII Formation. The interpolation of channel belts was further constrained by the net-to-gross ratios from adjacent wells.

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