Caspian pioneer: Structural complexity and hydrocarbon distribution in the Neft Dashlary offshore field

Huseynaga MAMMADOV; Murad ABDULLA-ZADA; Elena POGORELOVA

doi:10.17721/1728-2713.111.09

Authors

Huseynaga MAMMADOV Azerbaijan State Oil and Industry University
Murad ABDULLA-ZADA Azerbaijan State Oil and Industry University
Elena POGORELOVA Azerbaijan State Oil and Industry University

DOI:

https://doi.org/10.17721/1728-2713.111.09

Keywords:

Oil field, Productive Series, porosity, permeability, stratigraphy, tectonics, offshore zone, geophysical analysis

Abstract

Background. The Neft Dashlary (Oil Rocks) oil field is a geologically and historically unique offshore petroleum province, located in the southeastern sector of the Caspian Sea. As the first offshore field in the world to be developed directly on marine platforms, it has played a pioneering role in offshore hydrocarbon exploration and production. Geologically, the field occupies a structurally complex zone within the Absheron–Balakhany tectonic uplift and is situated atop a prominent northwest–southeasttrending brachyanticlinal fold. The reservoir system is primarily hosted within the Lower Pliocene Productive Series, which includes a multilayered assemblage of deltaic, coastal, and shallow-marine facies. Despite decades of production, the field remains a valuable subject for re-evaluation due to its reservoir heterogeneity, fault segmentation, and layered hydrocarbon distribution, which pose both challenges and opportunities for enhanced oil recovery and long-term development planning.

Methods. This study is based on a comprehensive analysis of geological, geophysical, petrophysical, and production data from more than 150 wells across the Neft Dashlary field. Core analyses (1,453 samples from 357 wells), well log interpretations, and test data were integrated to characterize reservoir properties and map hydrocarbon-saturated intervals. Reservoir architecture was reconstructed using stratigraphic correlations and structural contouring across tectonic blocks. Oil-in-place and recoverable volumes were estimated using deterministic volumetric methods. Faults and facies pinch-outs were analyzed to define reservoir continuity and trapping mechanisms.

Results. The Productive Series at Neft Dashlary comprises a multilayered reservoir system with oil-saturated intervals in 26 distinct stratigraphic objects across eight lithostratigraphic suites, including the Gala, Pre-Kirmaki, Kirmaki, and Post-Kirmaki sandy and clayey units. Reservoirs exhibit porosities of 12–28% and permeabilities from 0.001 to 3.92 µm², with facies and structural heterogeneity governing hydrocarbon distribution. The most prolific zones are found in the GS-1 and GS-2 horizons (Gala Suite), and in PKS-2a and PKS-2 (Pre-Kirmaki Suite), particularly within Blocks II, III, IV, and V. Block I consistently exhibits low reservoir quality and marginal saturation. Structural closures, lithological seals, and facies transitions control the extent of hydrocarbon accumulations, while free gas is rarely encountered.

Conclusions. The Neft Dashlary field demonstrates complex stratigraphic and structural controls on reservoir distribution and productivity. Integrated geological and petrophysical analysis reveals significant heterogeneity both laterally and vertically, requiring block-by-block reservoir management strategies. The identification of key productive intervals and their spatial delineation provides a basis for optimized recovery planning and extended field life.

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