Abstract
Current geological extraction theory and techniques are very limited to adequately characterize the unconventional oil-gas reservoirs because of the considerable complexity of the geological structures. Optical measurement has the advantages of non-interference with the earth magnetic fields, and is often useful in detecting various physical properties. One key parameter that can be detected using optical methods is the dielectric permittivity, which reflects the mineral and organic properties. Here we reported an oblique-incidence reflectivity difference (OIRD) technique that is sensitive to the dielectric and surface properties and can be applied to characterization of reservoir rocks, such as shale and sandstone core samples extracted from subsurface. The layered distribution of the dielectric properties in shales and the uniform distribution in sandstones are clearly identified using the OIRD signals. In shales, the micro-cracks and particle orientation result in directional changes of the dielectric and surface properties, and thus, the isotropy and anisotropy of the rock can be characterized by OIRD. As the dielectric and surface properties are closely related to the hydrocarbon-bearing features in oil-gas reservoirs, we believe that the precise measurement carried with OIRD can help in improving the recovery efficiency in well-drilling process.
Highlights
Variations in terms of the permeability in different directions
The weakness associated with cementation results in the damage to the lamination surface to precede the damage to the body
The sample was located on a two-dimensional (2-D) stage, and we set the direction of sample movement parallel to the bedding plane and adjusted the phase shifter and polarization analyzer to make the I(2 Ω) and I(1 Ω) signals equal to zero
Summary
Variations in terms of the permeability in different directions. In sonic logging, the propagation of acoustic waves reflects the obvious anisotropy in the geological strata[5]. After obtaining and precisely analyzing these logging data, hydraulic fracturing technology can be employed In this technique, fracturing fluid is poured into the reservoir at a pressure that exceeds the absorbing capacity of the oil reservoir. By combining CT scanning and digital image processing technology, the meso-damage characteristics of rock can be investigated during the process of shale hydration[12] We employed an optical technique, referred as oblique-incidence reflectivity difference (OIRD), of imaging the shale and sandstone surfaces for improved characterization of the anisotropy of shale and the isotropy of sandstone. Similar to the optical methods mentioned above, OIRD is insensitive to the interference of subsurface electromagnetic fields and to high subsurface temperature and pressure Compared with these methods, the OIRD technique is a more sensitive detection tool. The experimental results suggest that the OIRD technique can be used for core analysis required during oil-gas exploration and development, especially in the unconventional petroleum resource industry
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