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Abstract: Neogene Stratigraphy and Sedimentology in Eastern Azerbaijan: Outcrop Observations and Subsurface Implications

Ak. A Ali-Zade, I. S. Guliyev, E. Z. Ateava, R. O. Koshkarly, D. N. Mamedova, S. F. Suleymanova, M. B. J. Bowman, A.C. Brayshaw, G. Geehan, J. Henton, R. W. Jones, A. D. Reynolds, M. D. Simmons, T. Varney, G. M. Samways, P. Brenac, L. O. Allen

The largely Pliocene Productive Series of eastern Azerbaijan contains about 26 billion barrels oil equivalent. It is well exposed in outcrops on the Apsheron Peninsula which a joint team from the GIA and the BP and Statoil Alliance have described. Detailed biostratigraphic and petrographic studies have subsequently been carried out.

Productive Series deposition was initiated by a dramatic relative sea-level fall which left the South Caspian an isolated basin fed by deeply incised precursors to the modern Volga, Amu Darya, and Kura rivers. Five facies associations have been recognised within the Productive Series at outcrop, encompassing a range of palaeoenvironments from alluvial braided river sandstones and conglomerates to delta-front siltstones and mudstones. The facies associations suggest a river-dominated, braid delta.

Four idealised reservoir models can be recognised: fluvial, delta-plain, proximal delta-front and distal delta-front. Each has distinct grain-size and shale distributions. Studies of nearby oilfields suggest that these models form useful subsurface analogues. Flow simulation models suggest that each reservoir type has dramatically different performance.

Productive Series sediments are typically loosely cemented and smectite rich, which may result in clay swelling and sand control problems. Localised reduction in reservoir quality is caused by fault-associated calcite cements. Proximal facies of the upper Productive Series contain porosity occluding gypsum cements.

Palynology and nannopalaeontology have been applied to the Neogene sediments of Azerbaijan for almost the first time, and have given encouraging results, at least in terms of a broad biozonation. Micropalaeontological analyses have also provided useful palaeoenvironmental data.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France