| Pore structure and wettability are important in understanding the overall flow geometry and fluid distributions in reservoir rock which in turn affect the rate and overall recovery of oil from the reservoir. There are two parts to this study. In the first part, the aim is to study detailed micron-scale pore geometry in carbonate reservoirs to understand the relationship between pore structure and flow properties like permeability. In the second part, the focus is on the study of wettability alteration in sandstone reservoirs due to changes in the brine composition.;Two-dimensional sections of reservoir rocks are studied under an optical microscope to get pore structure information. The images of these sections are analyzed for properties of pore space like porosity, pore size distribution, chord length distribution, Fourier power spectrum and fractal dimension. Porosity, two point autocorrelation function and chord length distribution function are then used to construct a three-dimensional porous medium with the same statistical properties as the two-dimensional image. Pore size distribution, two-point autocorrelation function and Fourier power spectrum are also used to estimate permeability of the 3-D medium from the 2-D image analysis data. Permeability estimated from pore size distribution is within an order of magnitude of the measured permeability value for 80% of the samples.;In the second part of the work, simulation studies are done to study the tertiary water flood recoveries and flood front instabilities in 2-D low salinity floods. Wettability alteration is used to model effect of low salinity water injection by changing relative permeability and capillary pressure model parameters. A 1-D fingering theory is used to predict the extent of fingering in homogeneous porous media. Fingering is not severe and the length of fingers depends on the relative permeability model parameters, the capillary pressure gradient, dispersion, permeability distribution width and viscosity ratio of the oil and water phases. The leading edge fingers can be predicted using the fingering theory for cases where capillary pressure is negligible, the permeability field is almost homogeneous and the saturation shocks from the 1-D solution do not interfere. |
