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MODELING FLUID MIGRATION PATHWAYS IN THE AKSHABULAK AND ARYSKUM HYDROCARBON FIELDS USING SEISMIC-DERIVED GEOMECHANICAL PARAMETERS

Abzal Zhienbayev, Dinara Talgarbayeva, Arailym Gaipova, Bexultan Niyazbekov

Abstract

The Akshabulak and Aryskum structures, located within the Aryskum depression of the South Torgay sedimentary basin, are among the most thoroughly investigated hydrocarbon-bearing areas in Kazakhstan. The discovery of several oil and gas fields in these structures was facilitated by seismic surveys conducted between 1986 and 1988. The present study aims to develop predictive exploration models based on the analysis of density heterogeneities and the distribution of horizontal lithostatic pressure components derived from 3D seismic data. The modeling was performed using depth and time maps of key stratigraphic horizons, including the Lower Neocomian, Upper Jurassic, Middle Jurassic, and Paleozoic basement surfaces. These datasets were integrated into a unified three-dimensional framework that served as the basis for geomechanical and density modeling. To evaluate potential fluid migration pathways, the vertical stress component was excluded from calculations, allowing the analysis to focus on horizontal stress distributions controlling permeability and lateral fluid movement within the geological medium. The results indicate significant heterogeneity in the permeability structure of both study areas. Zones of reduced horizontal lithostatic pressure form vertically oriented weakened corridors that may serve as preferential pathways for hydrocarbon migration. In the Akshabulak structure, two major low-pressure channels spatially coincide with known hydrocarbon accumulations. Similar features were identified within the Aryskum structure, where numerous vertically developed migration pathways suggest favorable conditions for hydrocarbon accumulation in the presence of effective seals. Density models further confirm the existence of column-like low-density zones interpreted as fluid-conducting channels. The developed models do not directly identify hydrocarbon traps or reservoir units; however, they successfully delineate potential fluid migration pathways and provide additional criteria for assessing the petroleum prospectivity of structurally complex areas within the South Torgay Basin.

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