低渗砂岩储层数字岩心构建及渗流模拟

基于CT扫描的数字岩心技术是研究低渗砂岩储层内部微观孔喉特征及孔隙尺度渗流机理的有效途径。为直观、深入研究低渗砂岩储层微—纳米尺度流体输运特征,先通过Micro-CT扫描技术获取低渗介质多尺度三维灰度图像,统计轴向截面孔隙率分布整体考察岩心非均质程度;再结合三维重构及逆向工程技术,精准构建低渗介质复杂孔隙三维数字模型后并转换成CAD实体模型;再利用COMSOL建立多组表征单元体有限元模型,数值计算不同边界条件下微—纳米孔隙内流体输运特征;然后通过三维流线及孔隙压力分布场,动态可视化再现低渗介质渗流过程;最后对比常规渗流实验与数值模拟结果,分析两者差异的产生原因,并提出应用数字平台研究低渗岩石物性及渗流机理的深入关注点。文中研究成果为低渗油藏多尺度数字岩心建模及深层次微观渗流机理研究提供了思路。

Digital core construction and seepage simulation of low permeability sandstone reservoir

The digital core technology based on CT scanning is an effective way to study the microscopic characteristics of pore throat in low permeability sandstone reservoirs and the seepage mechanism at pore scale.In order to deeply study the transport characteristics of micro-nano scale fluid in low permeability sandstone reservoirs,following steps are implemented:first,the multiscale three-dimensional gray-scale images in low permeability are obtained by the technology of Micro-CT scanning and the core's heterogeneity degree comprehensively is analyzed through the statistics of axial cross-section porosity distribution;second,using three-dimensional reconstruction and reverse engineering technology,three-dimensional digital model of complex porosity and lowpermeability matrix is constructed accurately and then is converted into CAD solid model successfully;third,the finite element model of several groups of REV by using COMSOL is established,acquiring the transport characteristics of fluid in micro-pores under different boundary conditions through numerical calculation;fourth,the medium's seepage process in low permeability is reconstructed by analyzing the three-dimensional streamline,the distribution field of pore pressure,and the dynamic visualization technology;finally,after comparing the results between conventional seepage experiments and numerical simulation and analyzing the causes of these differences,some focus are put forward when studying the physical properties and percolation mechanism of low permeability rocks with the application of digital platform.This paper provides an idea for the modeling of multi-scale digital core and the research on microscopic seepage mechanism.