Research On The Microscopic Characteristics Of Y10 Reservoir And Its Influence On Residual Oil Distribution In MaLing Oil Field

Yan 10 reservoir in North Three Area of Maling oil field has been developed into the typical late medium-high water cut stage, water is quickly flooding along the high permeable zone after water injection, all of which lead to poor water displacement performance and low degree of geological reserves produced. In this paper, from the microscopic geological features and the relationship between oil and water movement rule, control factors of micro remaining oil distribution, we carried on the thorough analysis to the problem. Application of high pressure mercury injection, oil and water relative permeability, constant speed mercury penetration, nuclear magnetic resonance experiments to explore the microscopic pore structure and reservoir percolation characteristics, limited and divided the cutoff properties of reservoir and the seepage zone, carried on the experiment to the formation and distribution of microscopic remaining oil, discussed the formation mechanism and microscopic remaining oil distribution control factors under the condition of the water injection development. The main research results are as follows:(1) The reservoir pore distribution is concentrated(120μm～140μm), belongs to the larger pore-large pore, the average throat radius is 6.33μm, the distribution difference is great, they are micro-throat, fine-medium throat and wide throat. The heterogeneity of reservoir permeability is high and the seepage difference is obvious. Coarse pore throat has a great influence on seepage, it determines the permeability contribution principal value.(2) Pore combination type can be divided into three kinds, they are intergranular pores(27%), dissolved pores-intergranular pores(52%)and micropores(21%), mean value of movable fluid saturation is on the high side(83.94%), but in the oil-water relative permeability test results shows differences.The dissolved pores -intergranular pores samples’ moisture content increased slowly, the recovery rate decreased slowly. In water flooding experiment, injected water evenly to move; The intergranular pores samples’oil phase and water phase exchange ability is fast, the seepage of the space is not large. In water flooding experiment, water injection is finger-reticular breakthrough, it is easy to form the dominant channel. In the case of rising moisture content, oil phase permeability of micropores samples decrease rapidly, oil producing capacity decay quickly, the water flooding experiment of displacement condition is high.(3) The sedimentation and diagenesis transformed reservoir microscopic pore structure, in the process of oil and water seepage, the mutual interference between the wettability of rock and fluid properties and effects of temperature, pressure, water injection mode and other factors, which all control the study area reservoir oil displacement efficiency, microscopic remaining oil type and distribution.(4) The lower limit for immovable pore and throat radius of reservoir is 0.280μm, the invalid seepage range is 0.280μm～0.741μm, subjected to bending, narrow throat control; the normal seepage range is 0.741μm～4.571μm, controlled by the pore and throat, the permeability contribution is low, the mainstream of seepage range is>4.571μm, total amount of mercury is high, the seepage ability is high, preponderance flow path which prone to water channeling phenomenon’s average pore and throat radius in study area is 7.968μm.(5) Reservoir comprehensive classification combined with production status:class one(intergranular pores), the heterogeneity of reservoir pore and throat radius is strong, the initial yield is high, but for now, most have been flooded; class two (dissolved pores and intergranular pores), the reservoir water content is low, stable production cycle is long, the area of the plane distribution is big, the microscopic distribution is uniform, it is the goal of further development; class three (micropores), developing the micro throat, the pore structure is relatively poor, the driving conditions are relatively high, it is the low quality reservoir.