Research Status, Existing Problems, and the Prospect of New Methods of Determining the Lower Limit of the Physical Properties of Tight Sandstone Reservoirs

At present, many methods are used to determine the lower limits of physical properties (PPLLs) of tight sandstone reservoirs, such as empirical statistics, oil occurrence, and logging parameter crossplots, but the accuracy with which these methods obtain the lower limit of physical properties depends entirely on the number of test production data, and they are not suitable for tight sandstone reservoirs with a low degree of exploration and a lack of prediction. Compared to these mature methods, it can be concluded that the water-film-thickness-based method, which integrates factors such as formation temperature, formation pressure, mineral wettability, and formation water salinity, can characterize PPLLs using the minimum pore throat radius for hydrocarbon migration, which has a better theoretical basis and technical advantages. However, the water-film thickness is not a fixed value and cannot be directly measured in the laboratory. The molecular simulation method, known as a computational microscope, has become an effective means of investigating nano effects. By accurately investigating the interactions between rock minerals and the formation of water on atomic and molecular scales based on increasingly improved studies of the molecular force field, this method can overcome the deficiencies of the laboratory study of water films and precisely characterize the water films’ thickness. The intersection of molecular simulation and geology can bring about new methods and new research ideas for determining the lower limit of the physical properties of tight sandstone reservoirs and has broad application prospects.