Carbon dioxide reacts with porous media while flowing through them enhancing their permeability.Its flow behavior as well as the permeability enhancement effects were studied in synthetic cores,natural cores and microtubes with an inner diameter of 5 μm.The results show that the permeability of H2O-saturated cores(containing carbonate ingredients) was enhanced by increasing the injection volume of a CO2-H2O solution.This enhancement is attributable to carbon dioxide's corrosion,which is justified by SEM scanning.The same phenomenon occurs with a CO2-H2O solution in microtubes,but for a different reason.The gas flow velocity of carbon dioxide in microtubes was approximately 100% faster than that of nitrogen because of the scale and the squeezing effects.Carbon dioxide molecules dissolved in water accelerate the diffusion rate of water molecules within the boundary layer,which in turn diminishes the thickness of the water film and enlarges the effective pore size.This flow behavior facilitates the injection of carbon dioxide into low-permeability reservoirs for oil-displacement and formation energy buildup purposes.This behavior also increases the potential for carbon dioxide channeling or release from the formation.
The pore structural characteristics have been the key to the studies on the mechanisms of fluids flow in porous media. With the development of experimental technology, the modern high-resolution equipments are capable of capturing pore structure images with a resolution of microns. But so far only 3D volume data of millimeter-scale rock samples can be obtained losslessly. It is necessary to explore the way of virtually reconstructing larger volume digital samples of porous media with the representative structural characteristics of the pore space. This paper proposes a reconstruction method of porous media using the structural characteristics captured by the data templates of multiple-point geostatistics. In this method, the probability of each structural characteristic of a pore space is acquired first, and then these characteristics are reproduced according to the probabilities to present the real structural characteristics in the reconstructed images. Our experimental results have shown that: (i) the deviation of LBM computed permeability respectively on the virtually reconstructed sandstone and the original sample is less than 1.2%; (ii) the reconstructed sandstone and the original sample have similar structural characteristics demonstrated by the variogram curves.
ZHANG Ting 1,2,3, LI DaoLun 1,2 , LU DeTang 1,2 & YANG JiaQing 1,2 1 Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
The three-dimensional reconstruction of porous media is of great significance to the research of mechanisms of fluid flow. The real three-dimensional structural data of porous media are helpful to describe the irregular topologic structures in porous media. The reconstruction of porous media will be inaccurate while only hard data or no conditional data are available. Reconstructed results can be more accurate, using soft data during reconstruction. Integrating soft data with hard data, a method based on multiple-point geostatistics (MPS) is proposed to reconstruct three-dimensional structures of porous media. The variogram curves and permeability, computed by lattice Boltzmann method (LBM), of the reconstructed images and the target image obtained from real volume data were compared, showing that the structural characteristics of reconstructed porous media using both soft data and hard data as conditional data are most similar to those of real volume data.
LU DeTang1,2,3, ZHANG Ting1,2,3, YANG JiaQing1,2,3, LI DaoLun1,2,3 & KONG XiangYan1,2,3 1 Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
