STUDY ON PORE STRUCTURE OF TIGHT SAND BASED ON RESISTIVITY

Pore structure of tight sand reservoirs with low porosity and low permeability is an important factor influencing the storage capacity and recovery ratio, thus study of pore structural features is of great significance. This paper mainly discusses the methods to study the pore structural features of reservoirs with low permeability and porosity. Based on the pore structural features of this kind of reservoirs derived from the experimental data of cast thin section and mercury penetration, a model for calculating the pore structure parameters of tight sand reservoirs is built by using the bundle of capillary tubes pack, and is verified with the experimental data of lithology and electric properties. The pore structure parameters derived from resistivity parameters are variable with water saturation, and the magnitude and rate of their variations can reflect the change of fluid distribution in reservoirs in the recovery process. The pore throat radius calculated by using the measured resistivity downhole at different times can only reflect the radius of pore spaces that are occupied by conductive fluids at the time of logging, and the calculated tortuosity also can only reflect the current distribution of conductive fluids.