Abstract: Fine reservoir description is the basis and key for later exploration and EOR as well as keeping stable production of an aged oilfield. However, there exist uncertainties in study of single sand body connectivity and scale during fine reservoir description, due to lack of data and multiple solutions of geological interpretation. This paper developed the isochronous stratigraphic frameworks and sands overlap model by using high?resolution sequence stratigrphy method and analysis and correlation of comprehensive data to effectively guide the reservoir description and the single sand body anatomy. Taking the gas injected reservoir in Hei?59 block in Jilin oilfield as an example, the fine reservoir description and single sand body detailed anatomy have determined the vertical and lateral distribution of the reservoir, described the development stages and scale of single sand body, and realized the 3D visualization distribution of the sand bodies in this area