单砂体高部位油水倒置分布的成因机制

Oil/water Inversion and Its Genetic Mechanism in the Higher Portions of the Single Sandstone Body

成藏地质条件的复杂多变控制了油水分布的复杂性和多样性,尤其是在低渗透油藏中。断层圈闭油藏和岩性油藏中存在一种类似的油水倒置分布样式,即由单砂体高部位向低部位,依次为水层、含油水层、油水同层、油层、油水同层、含油水层、水层。通过分析两种油藏类型中低渗透砂体储层高部位油水倒置的控制因素,探讨了油水倒置的两种成因机制。分析结果表明,断层圈闭为主的油藏中,造成油水倒置的主要原因是断层封闭性的历史性差异,其次是储集层物性和渗透率级差;而上倾尖灭砂体岩性油藏中,造成油水倒置的主要因素是储集层物性及其变化,尤其是储层层内非均质性。同时,分析结果进一步表明,油水倒置系统中,存在低电阻率油层。

Complex and levity of geological conditions for forming oil reservoirs result in the complex and levity of oil/water distribution, especially, in low permeability reservoirs. There have one kind of oiL/water inversion in fault trap and lithologic oil reservoirs, that is, from the high portions of the single sandstone body to the low portions, they are water layer, water-bearing layer, oil-water layer, oil layer, oil-water layer, water-bearing layer, and water layer. According to analysis on the kinds of genesis mechanisms history diversity of the fault controlling factors of the oil/water inverted distribution in low permeability reservoirs, two were discussed. The results indicate that there have two status. First, in fault trap, the sealing is the key reason for the oil/water inverted distribution and physical properties of reservoir and permeability difference are the second reason. Second, in upward wedge out sandstone, physical properties of reservoir and its levity, especially, the heterogeneity of layer, are the key reasons for the oil/water inverted distribution. Meanwhile, The results indicate that they include the low-resistivity pay zone in the oil/water inversion system.