利用核磁共振研究特低渗透油藏微观剩余油分布

Microscopic Distribution of Remaining Oil of Ultra-low Permeability Reservoir by using NMR Technique

利用大庆外围油田特低渗透储层岩心,将特低渗透物理模拟实验和低磁场核磁共振仪相结合,建立了研究特低渗透油藏微观剩余油分布的新方法,分析了不同润湿性、不同驱替压力和不同含水阶段的微观剩余油分布规律.研究表明:亲水储层剩余油主要分布在中—大孔隙中,而亲油储层剩余油主要分布在中—小孔隙;随着驱替压力的增大,特低渗透储层剩余油饱和度降低,并且小孔隙中的剩余油变化较小,而中孔隙和大孔隙中的剩余油饱和度明显降低;小孔隙中的油主要在见水前阶段采出,见水后其剩余油饱和度变化较小,而见水后中—大孔隙中的剩余油饱和度降低比较显著.上述研究丰富了核磁共振技术在油田开发中的应用.

A new method combining with physical simulation experiments and nuclear magnetic resonance technique was established to study the microscopic distribution of remaining oil in ultr-low permeability reservoir. Meanwhile, the factors affecting the microscopic distribution of remaining oil such as wettability, pressure gradient and different water cut were also studied by using the new method. A larger number of waterflooding and NMR experiments on sandstones core samples originally located in Daqing oilfield were conducted. The experimental results indicated that most of the remaining oil was distributed in medium and large pores of water-wet reservoir but it was mainly situated in small and medium pores of oil-wet reservoir. The total remaining oil saturation and that located in large pores significantly decreased with the increase of displacement pressure gradient. However, the remaining oil located in small pores remained constant during the waterflooding process. The experimental also showed that the original oil located in small pores was mainly produced before water breakthrough, but the remaining oil located in medium and large pores constantly decreased before and after water breakthrough. The research results enriched the application of NMR technique in the development of oilfield.