Simulation of surfactant based enhanced oil recovery

Surfactant flooding is an important process for enhanced oil recovery. A substantial amount of remaining oil resides in reservoirs especially in carbonate oil reservoirs that have low primary and water-flood oil recovery. Most of the surfactant flooding studies to date has been performed in water-wet sandstone reservoirs. As a result, the effects of heterogeneity and wettability of carbonates on surfactant flooding efficiency are fairly unknown. The purpose of this simulation study was to determine the effects of wettability and wettability alteration on Dodecylbenzene Sulfonate surfactant flooding in carbonate reservoirs. This study used the multi-phase, multi-component, surfactant flooding simulator called UTCHEM. The base case results showed that additional 27.8% of oil recovered after water-flooding process. Sensitivity analyses of key parameters such as chemical slug size and concentrations, salinity, reservoir heterogeneity and surfactant adsorption were performed to optimize a surfactant design for a mixed-wet dolomite reservoir. The study was then extended to simulating wettability alteration during the field scale surfactant flood. The results of modeling the wettability alteration showed that significant differences in injectivity and oil recovery are caused by the changes in the mobility of the injected fluid. As the use of surfactant flooding spreads into the reservoir especially oil-wet and mixed-wet reservoirs, the importance of surfactant-based wettability alteration will become important

Quasiscarred modes and their branching behavior at an exceptional point

We study quasiscarring phenomenon and mode branching at an exceptional point (EP) in typically deformed microcavities. It is shown that quasiscarred (QS) modes are dominant in some mode group and their pattern can be understood by short-time ray dynamics near the critical line. As cavity deformation increases, high-Q and low-Q QS modes are branching in an opposite way, at an EP, into two robust mode types showing QS and diamond patterns, respectively. Similar branching behavior can be also found at another EP appearing at a higher deformation. This branching behavior of QS modes has its origin on the fact that an EP is a square-root branch point.Comment: 5 pages, 5 figure

Characterizations of realized metal-insulator-silicon-insulator-metal waveguides and nanochannel fabrication via insulator removal

We investigate experimentally metal-insulator-silicon-insulator-metal (MISIM) waveguides that are fabricated by using fully standard CMOS technology. They are hybrid plasmonic waveguides, and they have a feature that their insulator is replaceable with functional material. We explain a fabrication process for them and discuss fabrication results based on 8-inch silicon-on-insulator wafers. We measured the propagation characteristics of the MISIM waveguides that were actually fabricated to be connected to Si photonic waveguides through symmetric and asymmetric couplers. When incident light from an optical source has transverse electric (TE) polarization and its wavelength is 1318 or 1554 nm, their propagation losses are between 0.2 and 0.3 dB/mu m. Excess losses due to the symmetric couplers are around 0.5 dB, which are smaller than those due to the asymmetric couplers. Additional measurement results indicate that the MISIM waveguide supports a TE-polarized hybrid plasmonic mode. Finally, we explain a process of removing the insulator without affecting the remaining MISIM structure to fabricate similar to 30-nm-wide nanochannels which may be filled with functional material.open8

Scarred Resonances and Steady Probability Distribution in a Chaotic Microcavity

We investigate scarred resonances of a stadium-shaped chaotic microcavity. It is shown that two components with different chirality of the scarring pattern are slightly rotated in opposite ways from the underlying unstable periodic orbit, when the incident angles of the scarring pattern are close to the critical angle for total internal reflection. In addition, the correspondence of emission pattern with the scarring pattern disappears when the incident angles are much larger than the critical angle. The steady probability distribution gives a consistent explanation about these interesting phenomena and makes it possible to expect the emission pattern in the latter case.Comment: 4 pages, 5 figure