Research On Micro-Pore Structure And Seepage Characteristics In Chang 8₁ Sandstone Reservoir In Maling Oilfield

The research principal part of the paper is about tight sand reservoir with low hole, extra-low hole, extra-low permeability or ultra-low permeability. Taking the research on micro-pore structure and seepage characteristics in Chang 81 reservoir in Maling oilfield of Ordos Basin as an example, we get the following results:(1) The main sandstone types in Chang 81 tight reservoir are lithic arkose and arkose sandstone with high-medium sorting, medium-low compositional maturity and medium-high structure maturity. There are various types of diagenesis in Chang 81 tight reservoir in Maling oilfield. The main destructive diagenesis are compaction and pressure-solution, which belongs to the middle diagenetic stage A and early B.(2) The major influence factors of the extra-low permeability or ultra-low permeability tight sand reservoir are the distribution characteristics of pore and throat, the throat radius, and the connectivity characteristics. The movable fluid is mainly distributes in the effectively connecting pore and throat. The major influence factors of the movable fluid saturation and the distribution. The experiment results of the phase permeability show that the permeability is not the key parameter which is used to describe the micro-seepage characteristics.(3) Diagenesis facies are the reflection of diagenesis circumstance. Different diagenesis facies keeps different sedimentary characteristics and micro pore-throat structure. In addition, micro pore structure is the basis to analyze the advantage of reservoir development, and controls the characteristics and the evolution law of deposition and diagenesis. Besides, distribution characteristics of pore and throat dicide the seepage characteristics of the reservoir.