Classification and evaluation of tight reservoirs in Fuyu oil layer, Sanzhao Sag, Songliao Basin

Fine evaluation is mainly embodied in two aspects: fine classification and vertical subdivision. The tight reservoirs in Fuyu oil layer can be divided into three categories, namely Ⅰ-1, Ⅰ-2 and Ⅱ combined with the study of sedimentary and sandbody characteristics, and by means of constant pressure mercury injection, high pressure mercury injection and nano microcosmic analysis. The boundary between tight oil reservoirs and conventional reservoirs is porosity 12%, permeability 1×10^-3 μm², pore throat radius 350 nm. The remaining Ⅰ-1 and Ⅰ-2 classes, as well as the Ⅰ-2 and Ⅱ standards, respectively, with the porosity of 10% and 8%, permeability of 0.25×10^-3 μm² and 0.1×10^-3 μm² as the boundary, corresponding to the pore throat radius of 150 nm and 75 nm. Each layer of the sand groups contains only 1-2 sand bodies based on the fine study of the longitudinal subdivision layer. Ⅰ class reservoirs mainly developed in FⅠ2-1, FⅠ3-1 and FⅡ2-2 sand groups. The remaining resources of different types of tight oil are implemented by layer, and through tight oil horizontal well drilling and large volume fracturing, tight oil resources can be explored effectively.