大庆油田三元复合驱后微观剩余油分布特征

Distribution characteristics of the micro-remained oil after ASP flooding in Daqing Oilfield

为搞清三元复合驱后储层内微观剩余油分布特征,指导三元复合驱后剩余油精细挖潜,利用大庆油田三元复合驱试验区取心井岩心,开展油水饱和度检测及水驱、聚驱、三元复合驱驱油实验,采用激光共聚焦显微镜(LSCM)二维及三维成像技术,定性和定量地描述了复合驱后基于取心井的微观剩余油分布特征。结果表明:一是通过取心井岩心观察检测可知:复合驱后剩余油主要分布在采出端附近、河道砂体的中上部、隔夹层下部以及非河道砂体内,交错层理砂体段驱替较均匀,块状砂体段驱替差异较大,驱油效率下部大幅高于上部;二是将微观剩余油分为簇状、孔表薄膜状、喉道状、角隅状、粒间吸附状及粒内状等6种类型,通过定量分析可知:化学驱油效果明显,水驱、聚驱、三元复合驱的孔表薄膜状、簇状剩余油绝对含油饱和度依次下降;分布形态从连续到断续、从线状到油珠状、从凸形到凹形转变;簇状剩余油相对含油饱和度占50%以上,主要分布在局部低渗透部位,是复合驱后剩余油挖潜重点对象。

In order to make clear of the distribution characteristics of the micro-remained oil in the reservoir after ASP flooding and guide the fine tapping of the oil, using the cores of the coring well in the ASP-flooding test block of Daqing Oilfield, the oil-water saturation detection and water, polymer and ASP floodings' experiments were conducted, and moreover with the help of the laser confocal microscopy (LSCM) two-dimensional and three-dimensional imaging techniques, the micro-remained oil distribution characteristics were described qualitatively and quantitatively based on the coring well after the ASP flooding. The results show that first, it can be seen from the core observation of the coring well that the remained oil after the ASP flooding is mainly distributed near the produced end, in the upper-middle parts of the channel sandbody, the lower part of the interlayer and the non-channel sandbody;the staggered bedding sandbody interval is more evenly displaced, the displacement in the block sandbody interval is quite different, the oil displacement efficiency in the lower part is much higher than that of the upper part;secondly, the micro-remained oil can be divided into six types: cluster-like, membrane-like on the pore surface, throat-like, horn-like, intergranular adsorption and intragranular adsorption. By means of the quantitative analysis, it can be seen that the chemical flooding effects are obvious, the absolute contents of the film-like and cluster-like remained oil in the water flooding, polymer flooding and ASP flooding decrease in turn;the distribution patterns change from the continuous to intermittent, from linear to oily, from convex to concave;the relative content of the cluster remained oil accounts for more than 50%, the oil is mainly distributed in the partial low-permeability part, which is the key target of remained oil potential tapping after the ASP flooding.