Abstract: Classification and evaluation of effective reservoirs in deep tight sandstone is an important step in tight sandstone oil and gas evaluation. Due to the extremely low porosity and permeability of tight sandstone and the difficulty in guaranteeing the quality of the data, there are some limitations in the evaluation of reservoir quality by physical property parameters. According to the theory of reservoir filling and the combination relationship between reservoir and cap, based on the capillary pressure data of the study area and the effective stress data of the stratum, the calculation model of pore throat radius of sand and mud in the target stratum is established. It is considered that there is a large capillary pressure difference between the effective reservoir of tight sandstone and the adjacent cap, that is, the ratio of sand to mud pore throat is large. The limit value of sand/mud pore throat ratio of effective reservoir in the study area tends to increase with the increase of depth, and the better the reservoir quality is, the bigger the sand/mud pore throat ratio is. The application of practical data shows that the ratio of pore throat radius of sand and mudstone can effectively indicate the effectiveness of the reservoir, and the established reservoir classification criteria can be used to classify the effective reservoir in the study area by comparing with the tested output.

Key words: tight sandstone, effective reservoir, pore throat radius, classified evaluation, clustering analysis