Seg Technical Program Expanded Abstracts 

About: Seg Technical Program Expanded Abstracts is an academic journal. The journal publishes majorly in the area(s): Inversion (meteorology) & Seismic inversion. It has an ISSN identifier of 1052-3812. Over the lifetime, 23409 publications have been published receiving 119653 citations.

Imaging dispersion curves of surface waves on multi-channel record

Abstract: Summary Real and synthetic data verifies the wavefield transformation method described here converts surface waves on a shot gather directly into images of multi-mode dispersion curves. Pre-existing multi-channel processing methods require preparation of a shot gather with exceptionally large number of traces that cover wide range of source-to-receiver offsets for a reliable separation of different modes. This method constructs high-resolution images of dispersion curves with relatively small number of traces. The method is best suited for near-surface engineering project where surface coverage of a shot gather is often limited to near-source locations and higher-mode surface waves can be often generated with significant amount of energy.

Mapping Basement Magnetization Zones From Aeromagnetic Data In the San Juan Basin, New Mexico

Abstract: Two new techniques are employed in analysis of aeromagnetic data from the San Juan basin, New Mexico, to enhance the expression of buried basement structure and lithology: (1) the data are analytically continued downward onto the irregular basement surface in order to reduce the effect of variable depth to basement, and (2) magnetization boundaries are delineated by a linear filter based on the gradient of pseudogravity Reduction to the basement involves three procedures that, together, provide a practical method for continuation of potential fields between general surfaces Data are continued from the nonlevel flight-elevation surface onto a level surface (drape-tolevel continuation) by means of a system of successive approximations based on expansion of a Taylor series Data are continued from the new level surface downward to another level surface at the mean elevation of the basement (level-to-level continuation) by analytical downward continuation based on the fast Fourier transform, incorporating a high-cut filter Data are continued from this level onto the nonlevel basement surface (level-to-drape continuation) by direct evaluation of a truncated Taylor series expansion, in the vertical dimension, of the field represented on the level surface Magnetization boundaries are determined by evaluating the magnitude of the horizontal gradient of the pseudogravity transform of the magnetic data Lines drawn along ridges of the horizontal gradient mark inferred basement-magnetization boundaries After application of these techniques, the aeromagnetic data from the San Juan basin, New Mexico, revealed features of the Precambrian basement not evident, or only vaguely so, in the original data Together with scanty drill data, the aeromagnetic data indicate a 70-km-wide belt of predominantly metasupracrustal rocks trending east-northeast across the center of the basin Predominantly granitic terranes border this belt on the northwest and southeast Numerous magnetization boundaries tens of kilometers in length are identified Structural grain is strongly east-northeast; an area of prominent northerly trends occurs in the north-central part of the basin and locally elsewhere Cenozoic intrusive rocks are unquestionably aligned with basement structural grain Laramide and Neogene structures in general are not so aligned There is no evidence of large strike-slip displacement of basement structures within the area surveyed

Improved AVO Fluid Detection And Lithology Discrimination Using Lamé Petrophysical Parameters; “λρ”, μρ, λμ Fluid Stack”, From P And S Inversions.

Abstract: However the underlying physics in the wave equation; does not involve seismic velocities, but instead the ratio of density (p) to modulus (M). So converting velocity measurements to Lame’s modulii parameters of rigidity and incompressibility (h) offers new insight into the original governing rock property factor It will be shown that an improved identification of reservoir zones is possible by the enhanced sensitivity to pore fluids from pure compressibility, as well as lithologic variations represented by fundamental changes in rigidity, incompressibility, and density parameters as opposed to mixed parameters of seismic velocities. Theory, method and log analysis motivation Standard analysis methods given above, though appearing different, rely fundamentally on Vp, Vs and density variations, thereby masking the original modulus parameterization as mentioned. Some authors point out the need for a more physical insight afforded by rigidity (Wright 1984,Thomsen 1990,Castagna et al. 1993b) in the above equations. Castagna also indicates that the link between velocity and rock properties for pore fluid detection, is through the bulk modulus that is embedded in Vp. However both and more so Vp have the most sensitive pore fluid indicator diluted by varying factors of the rock matrix indicator (ie. non-pore fluid). This can be seen in the following relationships; and Recent AVO inversion schemes incorporate an explicit density term (Stewart 1995, Smith 1996) to potentially extract modulii, but as the number of unknowns increase and exceed the measured quantities (intercept and offset gradient amplitude) so these complex equations are less robust and the extracted values more inaccurate. From these observations the standard approaches may be considered either too insensitive or unnecessarily complex as rock property indicators. The proposal here is to use modulii/density relationships to velocities V or impedances I, given as; + and These relationships enable extraction of the orthogonal Lame parameters and from logs with measured density or and from seismic without known density. The simple derivations are; and = 2 = Note, Poisson’s ratio analysis being related to (Vp/Vs) 2 , comes closes to measuring the most “rock property sensitive”