岩心微观与油藏宏观剩余油临界描述尺度研究

The critical description scale study on core microscopic and reservoir macroscopic remaining oil

中国陆上油田已整体进入高含水开发期,地下油水关系日趋复杂,剩余油分布更加分散,准确揭示剩余油分布规律,为开发调整措施提供决策依据是亟待解决的难题。利用人工石英砂制作岩心模型,借助微焦点CT系统对岩心模型进行CT切片扫描,在对二维切片进行图像预处理、插值、分割的基础上,对CT切片图像进行三维重建,得到了岩心三维孔喉结构及油水分布情况。基于岩心三维孔喉模型,发现岩心孔喉微观剩余油具有连续、连续—离散、离散等不同分布特征,由离散特征向连续特征转化的临界描述尺度下限为45μm(约为孔喉半径的2倍)、临界描述尺度上限为167μm(约为孔喉半径的7.6倍);基于油藏数值模拟技术,得到了油藏宏观剩余油合理临界描述尺度,当网格尺寸不高于油藏宏观剩余油临界描述尺度时,模拟结果能够有效刻画油藏宏观剩余油局部富集现象。

At present, Chinese onshore fields have generally stepped into high water cut stage. The relationship between oil and water gradually becomes complex and the remaining oil is more dispersed. It's a pressing problem to accurately reveal the distribution of the remaining oil which can provide decision-making for development adjustment measures. The core model filled with artificial quartz sand was adopted. A series of CT slice images describing microscopic pore structure and fluid distribution of the core model were obtained with the help of the micro-focus CT system. On the basis of scanned slices, three-dimensional visualization of pore structure and fluid distribution was achieved with a series of image processing methods, including pre-processing, interpolation, segmentationscopic pores has different distribution features as'continuous, discrete, continuous-discrete transition', which determines that its critical description scale from discrete feature converted to continuous feature is 2 to 7.6 times of the pore radius; on the basis of reservoir numerical simulation technology, this paper proposed the critical description scale of the reservoir macroscopic remaining oil. The research indicates that when the grid size is not higher than the critical description scale of the reservoir macroscopic remaining oil, the simulation results can effectively characterize the local enrichment phenomenon of the reservoir macroscopic remaining oil.