Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, California 94550, United States.
Environ Sci Technol. 2013 Jan 2;47(1):262-8. doi: 10.1021/es3012723. Epub 2012 Aug 23.
We present characterization and geochemical data from a core-flooding experiment on a sample from the Three Fingers evaporite unit forming the lower extent of caprock at the Weyburn-Midale reservoir, Canada. This low-permeability sample was characterized in detail using X-ray computed microtomography before and after exposure to CO(2)-acidified brine, allowing mineral phase and voidspace distributions to be quantified in three dimensions. Solution chemistry indicated that CO(2)-acidified brine preferentially dissolved dolomite until saturation was attained, while anhydrite remained unreactive. Dolomite dissolution contributed to increases in bulk permeability through the formation of a localized channel, guided by microfractures as well as porosity and reactive phase distributions aligned with depositional bedding. An indirect effect of carbonate mineral reactivity with CO(2)-acidified solution is voidspace generation through physical transport of anhydrite freed from the rock matrix following dissolution of dolomite. The development of high permeability fast pathways in this experiment highlights the role of carbonate content and potential fracture orientations in evaporite caprock formations considered for both geologic carbon sequestration and CO(2)-enhanced oil recovery operations.
我们介绍了来自加拿大 Weyburn-Midale 储层盖层下部三指蒸发岩单元的岩芯驱替实验的特征描述和地球化学数据。该低渗透样品在暴露于 CO2-酸化卤水前后使用 X 射线计算机微断层扫描进行了详细表征，允许在三维空间中定量矿物相和空隙空间的分布。溶液化学表明，CO2-酸化卤水优先溶解白云石，直到达到饱和，而硬石膏仍然没有反应。白云石的溶解通过局部通道的形成导致了整体渗透率的增加，这些通道由微裂缝以及与沉积层理一致的孔隙度和反应相分布引导。碳酸盐矿物与 CO2-酸化溶液反应的间接影响是通过白云石溶解后从岩石基质中释放出的硬石膏的物理输运产生的空隙空间。在这个实验中，高渗透率快速通道的发展突出了碳酸盐含量和潜在裂缝方向在考虑地质碳封存和 CO2 增强采油作业的蒸发岩盖层中的作用。
