Perpustakaan Digital ITB

In large petroliferous basins, tight and conventional reservoirs are widely distributed. These reservoirs have significant differences in formation mechanisms, enrichment rules, and development modes. Only when a reservoir petrophysical property is less than a certain upper limit can a large area of tight oil accumulation be formed. Therefore, it is necessary to scientifically define the petrophysical property boundary between tight and conventional reservoirs. In the past, the determination of petrophysical property boundaries between tight and conventional reservoirs was based mainly on the statistics of a large number of measured petrophysical property data of typical tight oil basins and lacked theoretical research. Taking the Ordos and Songliao Basins as examples, this paper studies the petrophysical upper limits of tight reservoirs, starting with the reservoir-forming mechanism and characteristics of tight and conventional reservoirs. Based on four methods—the mechanical balance method assuming that the buoyancy and capillary pressure are equal, petrophysical simulation of an oil accumulation in sandstone, analysis of the distribution characteristics of the current petrophysical properties of conventional and tight oil reservoirs, and mercury injection porosimetry tests to determine the change in reservoir porosity and permeability with displacement pressure—this research determines that basically the same upper limits of tight reservoir properties are found among these methods. Obtained synthetically, the upper limit of permeability is approximately 1 md, corresponding to the upper limit of porosity of approximately 12%. These research results provide new ideas and methods to distinguish tight oil from conventional oil accumulations in petroliferous basins in different stages of exploration.