海相碎屑岩储层不同尺度微观剩余油分布及赋存状态——以哈得逊油田东河砂岩为例

基于常规物性、扫描电镜、铸体薄片、压汞测试等资料，对哈得逊油田东河砂岩的孔喉结构进行划分，选取各类型孔喉结构的典型岩心，通过微观刻蚀薄片驱替实验及水驱油过程的核磁共振、CT扫描研究微观剩余油不同尺度下的分布特征、赋存状态和动用机理。结果表明：研究区存在小孔细微喉-低渗储层、中孔细喉-中渗储层和大孔中喉-高渗储层。微观剩余油可分为单一孔喉尺度的原始状态型、孔内分散型、表面吸附型和角隅型剩余油，局部孔喉组合尺度的斑块状、多孔状和单孔状剩余油，岩心样品尺度的连片状富集、分散状富集和星点状富集剩余油。剩余油主要赋存于中、小孔喉内，赋存状态上分为离颗粒表面较远的游离态剩余油和颗粒表面的水驱难动用束缚态剩余油。随着孔喉结构的变好，孔内分散型剩余油比例有所增加，斑块状剩余油比例下降，剩余油星点状富集增强，束缚态剩余油逐渐减少。油层注水开发后，中、小孔喉内游离态的原始状态型剩余油比例最大，是后期重点挖潜对象，可以采用注微球封堵大孔喉后续水驱的方式进行开采，其潜力大小与游离态剩余油总量相近。

Distribution and occurrence status of microscopic remaining oil at different scales in marine clastic reservoirs: a case study of Donghe sandstone in Hadeson oilfield

Based on conventional physical properties, scanning electronic microscope, casting slices, mercury injection test and other data, the pore-throat structure of Donghe sandstone in Hadeson oilfield is divided to select the typical cores of pore-throat structure in all types. The distribution characteristics, occurrence status and mobilization mechanism of microscopic remaining oil at different scales are studied by the nuclear magnetic resonance and CT scanning in micro etching thin-section displacement experiment and water-oil displacement process. The results show that the low-permeability reservoirs with micro-pore and tiny throat, mid-permeability reservoirs with meso pore-thin throat and high-permeability reservoirs with macro pore-medium throat exist in the study area. Microscopic remaining oil can be divided into the remaining oil at single pore-throat scale including original state type, intra-pore discrete type, surface adsorption type and corner stranded type, that at partial pore-throat combined scale characterized with plaque shape, multi-pore shape and single-pore shape, and that at the core sample scale with continuous enrichment, scattered enrichment and sporadic enrichment type. Remaining oil mainly occurs within meso-micro pore throat, divided by occurrence status into the remaining oil in a free state far away from grain surface and that in a bound state difficult to be mobilized by water flooding on grain surface. With the improvement of pore-throat structure, the proportion of remaining oil of the intra-pore discrete type is increased, while that of the plaque-shaped remaining oil is decreased, and the sporadic enrichment of remaining oil is enhanced, but the remaining oil in a bound state is gradually reduced. After the development of water flooding in reservoirs, the original remaining oil in a free state in the middle and small pore throat accounts for the largest proportion as the main target for later exploitation, which can be exploited by injecting microspheres to block the large pore throat and subsequent water flooding, and the potential is similar to the total amount of free remaining oil.