A case study of azimuthal AVO analysis with anisotropic spreading correction
Geomechanical properties of tight, low-porosity reservoirs are largely governed by natural fracture networks. Hence, reliable estimation of fracture density and orientation is extremely important for cost-effective hydraulic completion and hydrocarbon production. Direct information about fracturing can be obtained using borehole methods, such as image log analysis, which provide estimates of fracture counts and orientations on various scales. The main shortcoming of borehole measurements is that they are sensitive only to formation properties in the immediate vicinity of the well. In some cases, the spatial distribution of fractures can be inferred from fault maps obtained by coherence analysis of surface seismic data. However, the correlation between areas of high fracture density and fault locations is not always straightforward.
eismic anisotropy in exploration and eservoir characterization: An overview
Recent advances in parameter estimation and seismic processing have allowed incorporation of anisotropic models into a wide range of seismic methods. In particular, vertical and tilted transverse isotropy are currently treated as an integral part of velocity fields employed in prestack depth migration algorithms, especially those based on the wave equation. We briefly review the state of the art in modeling, processing, and inversion of seismic data for anisotropic media. Topics include optimal parameterization, body-wave modeling methods, P-wave velocity analysis and imaging, processing in the -p domain, anisotropy estimation from vertical-seismic-profiling VSP surveys, moveout inversion of wide-azimuth data, amplitude-variation-with-offset AVO analysis, processing and applications of shear and mode-converted waves, and fracture characterization. When outlining future trends in anisotropy studies, we emphasize that continued progress in data-acquisition technology is likely to spur transition from transverse isotropy to lower anisotropic symmetries e.g., orthorhombic . Further development of inversion and processing methods for such realistic anisotropic models should facilitate effective application of anisotropy parameters in lithology discrimination, fracture detection, and time-lapse seismology.
Analysis of the Ionospheric Effect for Time Offsets per GPS Code Measurements
This paper shows the analysis results of time offsets using P1, P2 and P3 code in GPS time transfer. The r2cggtts program has been used in GNSS Time Transfer and use the P3 ionosphere free combination of P1 and P2 code measurements. We modified the r2cggtts program in order to calculate and write all kinds of time offsets P3 as well as P1 and P2. The result of the modified r2cggtts program shows that time offsets using P1 and P2 are of wide distribution comparing to time offsets using P3. In order to Figure out the error factors for wide distributions of P1 and P2, we analyze and present the relation between the elevation angle and time offsets in this paper.