Research On Fine And Quantified Characterization Of The Pore Structure In Low Permeability Reservoir

Combining the research on the microscopic characteristics, of high pressure Hg injection, of rate-controlled Hg penetration,of NMR, of Laser Scanning Confocal Microscopy and Rock and Mineral Analysis,many studies have been done on the micro-pore structure in the low permeability reservoir of Jiyang Depression. Many conclusions have been received in research on fine and Quantified characterization of the pore structure in low permeability reservoir:The micro-pore structure in the low permeability reservoir is very complicated. Its distribution is characterized by multi-scale and strong heterogeneity. Positive correlation between permeability and porosity is significant, overall permeability increases with increasing porosity. But there is a more prominent contradiction which permeability changes great difference corresponding to the same porosity, similarly, porosity changes great difference corresponding to the same permeability. Simply use the porosity and permeability is difficult to accurately characterize the microscopic features.With the technical methods mentioned above, characteristic of the micro-pore structure of low permeability reservoir is finely portrayed. Special ultra-low permeability reservoirs are mainly developed nanoscale pore-throat and pores are mainly controlled by less than 0.1μm throat,Ultra-low permeability reservoirs are developed nano-micron pore throat and its porosity is mainly composed of micron-and nano-scale of the throat, Generally low permeability reservoirs are mainly developed micron pore throat and pores are mainly controlled by micron-scale of the throat. Pore throat radius distribution broadens with increasing penetration, the peak pore throat radius and the proportion of large pore throat also increases. The poorly throat is a major factor in the low permeability reservoir, the throats are commonly filled with carbonate cement, siliceous cement, authigenic kaolinite and so on, which making the flow properties of the reservoir greatly reduced. The large pore throat occuping a smaller volume plays a major contribution on permeability, the small throat contributes lower rate of penetration although with large volume.Difference between the original deposition conditions controls the difference between the detrital material and original micro-pore structure of low permeability reservoir. The original micro-pore structure would experience the different types of diagenetic fluids and different intensity of diagenesis in the process of burial. Original deposition conditions and post-diagenetic transformation is the main reason for the nowadays difference between the pore structure.On the basis of the analysis of the differences of pore structure, comprehensive low permeability reservoir porosity, throat and pore throat types and combinations of other characteristic parameters, the pore structure types of beach bar and turbidite sandstone reservoirs are fine-grained, which provides a basis for evaluation of reservoir.There must have nature, necessarily linked relationship between reservoir parameters and the micro-pore structure. On the basis of correlation analysis of the microscopic pore structure and macroscopic parameters, two methods quantified characterization of pore structure have been established. One is based on the reservoir quality index and pore throat invalid content,the other is used the macroscopic parameters multiple fitting.