Relationship between dynamic change of flow unit and distribution of remaining oil before and after the development of tight oil reservoir

Taking the Chang 8 tight reservoir in Ordos Basin as an example, the cluster analysis method is used to divide the reservoir into four types of initial flow units according to the five static parameters of effective thickness, porosity, permeability, reservoir quality factor, and oil saturation. On the basis of static parameters, the reservoir in the study area is divided into four types of developed flow units according to the two dynamic parameters of reservoir sand strength and liquid production. The three-dimensional modeling of the flow units before and after development is carried out, and the distribution characteristics of the flow units are analyzed. Combined with the numerical simulation of remaining oil, some suggestions are put forward for the subsequent reservoir potential tapping scheme. The research shows that the distribution of sedimentary facies controls the distribution of static flow units, and the high-level flow units extend along the main channel. The thickness of sand bodies is large, and the sand bodies are superimposed and continuously distributed. The low-level flow units are distributed on both sides of the main channel, the thickness of the sand body becomes smaller, and the sand body is separated. The development method controls the dynamic flow unit. After fracturing, the flow unit around the well is generally better than the inter well flow unit. After stage oil recovery and fracturing, the fluidity of the Class A and Class B of flow unit and the initial high value of oil saturation increases while the oil saturation decreases, resulting in the remaining oil-rich area being transformed into Class C and Class D flow units with relatively poor fluidity. Based on the distribution of developed flow units and the distribution characteristics of remaining oil, the reservoir can be divided into six potential tapping levels. The remaining oil content and developed flow unit level of the first-level potential tapping reservoir are high, which is the preferred area for the next production and development. The developed flow unit level of the second-level potential tapping reservoir is low but the remaining oil content is high, which can be jointly developed with the first-level potential tapping reservoir. The research provides reference for the study of flow units and the adjustment of later development schemes in the same type of tight oil reservoirs.