Alhosani Abdulla, Scanziani Alessio, Lin Qingyang, Foroughi Sajjad, Alhammadi Amer M, Blunt Martin J, Bijeljic Branko
Department of Earth Science and Engineering, Imperial College London, London SW7 2BP, United Kingdom.
Phys Rev E. 2020 Aug;102(2-1):023110. doi: 10.1103/PhysRevE.102.023110.
We use fast synchrotron x-ray microtomography to investigate the pore-scale dynamics of water injection in an oil-wet carbonate reservoir rock at subsurface conditions. We measure, in situ, the geometric contact angles to confirm the oil-wet nature of the rock and define the displacement contact angles using an energy-balance-based approach. We observe that the displacement of oil by water is a drainagelike process, where water advances as a connected front displacing oil in the center of the pores, confining the oil to wetting layers. The displacement is an invasion percolation process, where throats, the restrictions between pores, fill in order of size, with the largest available throats filled first. In our heterogeneous carbonate rock, the displacement is predominantly size controlled; wettability has a smaller effect, due to the wide range of pore and throat sizes, as well as largely oil-wet surfaces. Wettability only has an impact early in the displacement, where the less oil-wet pores fill by water first. We observe drainage associated pore-filling dynamics including Haines jumps and snap-off events. Haines jumps occur on single- and/or multiple-pore levels accompanied by the rearrangement of water in the pore space to allow the rapid filling. Snap-off events are observed both locally and distally and the capillary pressure of the trapped water ganglia is shown to reach a new capillary equilibrium state. We measure the curvature of the oil-water interface. We find that the total curvature, the sum of the curvatures in orthogonal directions, is negative, giving a negative capillary pressure, consistent with oil-wet conditions, where displacement occurs as the water pressure exceeds that of the oil. However, the product of the principal curvatures, the Gaussian curvature, is generally negative, meaning that water bulges into oil in one direction, while oil bulges into water in the other. A negative Gaussian curvature provides a topological quantification of the good connectivity of the phases throughout the displacement.
我们使用快速同步加速器X射线显微断层扫描技术，研究地下条件下油湿碳酸盐岩储层岩石中注水的孔隙尺度动力学。我们原位测量几何接触角，以确认岩石的油湿性质，并使用基于能量平衡的方法定义驱替接触角。我们观察到水驱油是一个类似排水的过程，水以连通前缘的形式推进，在孔隙中心驱替油，将油限制在润湿层中。驱替是一个侵入渗流过程，孔隙之间的狭窄通道（喉道）按尺寸顺序填充，先填充最大的可用喉道。在我们的非均质碳酸盐岩中，驱替主要受尺寸控制；由于孔隙和喉道尺寸范围广泛以及表面大多为油湿，润湿性的影响较小。润湿性仅在驱替早期有影响，此时油湿程度较低的孔隙首先被水填充。我们观察到与排水相关的孔隙填充动力学，包括海恩斯跳跃和液桥断裂事件。海恩斯跳跃发生在单孔和/或多孔水平上，伴随着孔隙空间中水的重新排列以实现快速填充。在局部和远处都观察到了液桥断裂事件，并且被困水团的毛细管压力显示达到了新的毛细管平衡状态。我们测量油水界面的曲率。我们发现总曲率（正交方向曲率之和）为负，给出负的毛细管压力，这与油湿条件一致，即当水压超过油压时发生驱替。然而，主曲率之积（高斯曲率）通常为负，这意味着水在一个方向上向油中凸起，而油在另一个方向上向水中凸起。负的高斯曲率为整个驱替过程中各相的良好连通性提供了一种拓扑量化。
