Identification of Astronomical Cycles and Prediction of High-Quality Reservoir Development in Lacustrine Carbonates:A Case Study of the Fourth Member of Shahejie Formation in Leijia Area,Western Sag
Hu Changhao
Xi Zhenzhu
Chen Chang
Li Yang
Abstract：Multiple sets of lacustrine carbonate rocks are developed in the fourth member of the Shahejie Formation(Es4)in the Leijia area of the western sag of the Liaohe Depression.With favorable geological conditions and promising resource potential,this interval currently serves as the primary target for tight oil exploration in the region.To clarify the characteristics of high-quality reservoirs and define exploration targets,this study integrates cyclostratigraphy,drilling,logging,seismic inversion,and analytical testing data to identify astronomical cycles and analyze reservoir properties,aiming to predict the distribution of high-quality"sweet spot"reservoirs.The main findings are as follows.(1)The Es4 member contains approximately six long eccentricity cycles and nineteen short eccentricity cycles,and the relationship between long eccentricity cycles and oil-bearing intervals in the area is elucidated.(2)High-quality reservoirs in the Leijia area are dominated by dolomite,characterized by fine dolomite crystals(mostly 1-3 μm),well-developed intercrystalline pores and structural fractures,micropores mainly distributed in the 0.3-0.4 μm range,effective throat lengths ranging from 1 to 20 μm,and pore volumes primarily between 0.5-4.0 μm³.Light oil components are mainly hosted within fractures and intercrystalline pores.These tight and brittle dolomites are primarily developed within the Du-3 oil layer.(3)A single-well evaluation was conducted using a multi-parameter fusion method to establish reservoir evaluation criteria.Combined with pre-stack geological inversion data,the study clarified the distribution pattern of high-quality sweet spots within the sequence stratigraphic framework and carried out planar prediction.This research systematically refines the stratigraphy and sedimentary reservoir characteristics of lacustrine carbonates in the Es4 member of the western sag,and effectively identifies sweet spot distribution using pre-stack seismic inversion,providing a robust geological basis for tight oil exploration in the area.
Keywords：lacustrine carbonateastronomical cycleshigh-quality reservoirsweet spot predictionwestern sagpetroleum geology
Publication Date：2025-12-30
Online Publishing Date：2026-01-26(First online date of this platform, not the publication date of the document)
Pages：21( 4715-4735 )