Tight sandstone reservoir is highly heterogeneous and its hydrocarbon accumulation process is complicated.The petrologic features

physical properties

pore throat structures and diagenesis of the Putaohua oil reservoir in Gulong syncline

Songliao Basin

were studied via a combination of core

thin section

SEM and experimental data.Then the spatio-temporal coupling relationship between the tightening history and hydrocarbon accumulation history of tight sandstone reservoir was analyzed based on the hierarchical system of architecture theory and the identification of genetic units.Results indicate that (1) hierarchically the Putaohua oil reservoir is composed of 8 lithofacies units

1 subfacies unit

and 4 microfacies units in terms of genesis;(2) the reservoir sandstone is mainly feldspar lithic sandstone with fine-grain size

medium sorting and rounding

mostly calcite cement filling

an average porosity of 7.63% and an average permeability 0.42×10

-3

μm

2

.The majority of the pores are intergranular dissolution pores

developing shrinkage

fracture

and curved-plate throats;(3) the Putaohua oil reservoir is currently in Period A of the anadiagenetic stage after two periods of cementation and one period of dissolution during the diagenetic evolutionary history;(4) the oil enrichment of the Putaohua reservoir is attributed to the dynamic evolutionary process of multiphase accumulation and selective charging.And we come to the conclusion that microfacies of the underwater channel

thick sheet sandstone

and the interconnected thin sheet sandstone close to the above two areas are high-quality hydrocarbon-enriched reservoirs in the syncline.