Seismic techniques for direct hydrocarbon indication rely on the changes in seismic character which accompany changes in pore fluid content. Interpretation and modeling of direct hydrocarbon indicators (DHIs) require an understanding of the factors affecting seismic velocities and reflection coefficients which are, in turn, dependent on pore fluid properties, rock frame properties, and fluid su...

A novel and rather simple method is presented to describe the physics of space-charge region in a planar diode. The method deals with the issue in the time domain and as a consequence transient time behavior can be achieved. Potential distributions and currents obtained using this technique, supposing zero initial velocity for electrons, reveal absolute agreement with Child's results. Moreover,...

Measuring reflection amplitude versus offset (AVO) has proved to be effective in reservoir characterization. Experience shows that AVO inversion methods based on amplitude-preserved prestack migration typically provides a more accurate lithology estimate than NMO-based AVO analysis. However, some artifacts may be introduced into the migration section due to an undersampled acquisition geometry,...

The propagation of shear waves in an anisotropic fluid saturated porous layer over a prestressed semi-infinite homogeneous elastic half-space lying under an elastic homogeneous layer with irregularity present at the interface with rigid boundary has been studied. The rectangular irregularity has been taken in the half-space. The dispersion equation for shear waves is derived by using the pertur...

We introduce a novel technique for seismic wave extrapolation in time. The technique involves cascading a Fourier Transform operator and a finite difference operator to form a chain operator: Fourier Finite Differences (FFD). We derive the FFD operator from a pseudo-analytical solution of the acoustic wave equation. 2-D synthetic examples demonstrate that the FFD operator can have high accuracy...

acetylation is a chemical modification of wood to enhance its properties. ir-spectroscopy is a useful technique for proofing chemical bondings in wood and the at-tenuated total reflection (atr) infrared spectroscopy technique was applied as an eas-ier technique over other ir-spectroscopies. in this research, different degrees of acetyla-tion, weight percentage gains (wpgs) in beech and pine min...

Existing algorithms for inversion of dispersion-curves estimated from analyzing the seismic surface-wave data provide a reasonable representation of the overall shear-wave velocity structure. However, in some cases these results may not meet the resolution requirement of the survey objectives targeting the upper portion of the subsurface section. Near-surface geophysical surveys often look for ...

Oil and gas production from tight, fractured reservoirs (sandstone, carbonates and shale) has increased significantly over the last decade. These hard rock targets are often characterized by vertically aligned fractures (i.e. HTI) embedded in a layered sequence (i.e. VTI). In this geologic setting, seismic velocities and η can vary with azimuth and depth. This is orthorhombic anisotropy and can...

The objective of seismic imaging is to obtain an image of the subsurface reflectors, which is very important for estimating whether a reservoir is beneficial for oil/gas exploration or not. It can also provide the relative changes or absolute values of three elastic parameters: compressional wave velocity Vp, shear wave velocity Vs , and density ρ. Two ways can achieve the objectives. In approa...

earthquakes travel times inversion for determination of velocity structure of crust is one of the most important objectives in seismology. in the simultaneous inversion method, the parameters of earthquakes and velocity model are determined initially and are improved during inversion steps. in this study, we have used more than 22000 calculated travel times for first arrivals of 6000 earthquake...