基于多尺度X-CT成像的数字岩心技术在碳酸盐岩储层微观孔隙结构研究中的应用

为了更加直观、准确地刻画碳酸盐岩储集层的微观孔隙结构特征,分别选取裂缝发育的双孔介质碳酸盐岩储层样品与裂缝不发育的单介质碳酸盐岩储层样品,利用多尺度X-CT扫描成像技术建立不同级别的三维数字岩心,应用最大球算法与孔喉尺寸校正方法,提取并建立碳酸盐储层纳米级数字岩心孔隙网络模型,最后实现利用三维孔隙网络模型模拟储层物性参数、进汞曲线以及孔、喉分布曲线,并与常规高压压汞法结果进行平行对比。研究结果表明:利用数字岩心技术模拟得到的孔隙度、渗透率参数与实际测量结果相差较小;模拟得到的进汞曲线、孔喉分布曲线与室内压汞实验得到的曲线具有较高的一致性,数字岩心得到的模拟结果具有较高的可信度。数字岩心技术在碳酸盐储层微观孔隙结构的直观刻画与定量描述方面,具有明显优势。

Application of Multiscale X-CT Imaging Digital Core Technique on Observing Micro-pore Structure of Carbonate Reservoirs

In this paper, we analyzed two types of core samples from porous carbonate reservoir via X-CT imaging to better constrain their microscopic pore structural features. The two sample types are namely the double porosity medium with fracture development and single porosity medium with no fractures. Three dimensional (3D) digital cores of different levels are established via the multi-scale X-CT scanning imaging technology, using the maximal ball algorithm and the method for pore and throat size correction, and consequently the digital cores nanoscale pore network model in carbonate reservoirs are extracted and established. Finally, the 3D pore network model is used to simulate the reservoir physical parameters, mercury injection curves and the pore and throat distribution curves, and the results are compared with those generated by the conventional high-pressure mercury injection method. The results show that the porosity and permeability parameters obtained by using the digital core technology are smaller than the actual measurements. The simulated mercury injection curves and pore throat distribution curves are in good agreement with those obtained by the laboratory mercury intrusion experiment, demonstrating that this technique is reliable. Digital core technology has clear strengths in directly and quantitatively described the micro-pore structure of carbonate reservoirs.