Hu Tianyue

How accurate can a well tie be

There appears to be a body of opinion among geophysicists that well‐log synthetic seismograms and seismic data cannot be expected to match one another very closely. For example, Simmons and Backus (Geophysics, 1996), in a paper on impedance estimation, state “…as is most often true, well‐log‐based synthetic seismograms do not agree well with observed seismic data.” Norman Neidell, in conjecturing on the conditions that generate coherent multiple reflections (TLE, November 1993) comments that explorationists often encounter synthetic seismogram fits that are less than satisfactory. That may be true, but it is not inevitable. We wish to counter these pessimistic views by showing an example of how good a well tie can be.

The Precise Finite Difference Method for Seismic Modeling

Abstract3-D seismic modeling can be used to study the propagation of seismic wave exactly and it is also a tool of 3-D seismic data processing and interpretation. In this paper the arbitrary difference and precise integration are used to solve seismic wave equation, which means difference scheme for space domain and analytic integration for time domain. Both the principle and algorithm of this method are introduced in the paper. Based on the theory, the numerical examples prove that this hybrid method can lead to higher accuracy than the traditional finite difference method and the solution is very close to the exact one. Also the seismic modeling examples show the good performance of this method even in the case of complex surface conditions and complicated structures.

A meshless method for acoustic and elastic modeling

Wave equation method is one of the fundamental techniques for seismic modeling and imaging. In this paper the element-free-method (EFM) was used to solve acoustic and elastic equations. The key point of this method is no need of elements, which makes nodes free from the elemental restraint. Besides, the moving-least-squares (MLS) criterion in EFM leads to a high accuracy and smooth derivatives. The theories of EFM for both acoustic and elastic wave equations as well as absorbing boundary conditions were discussed respectively. Furthermore, some pre-stack models were used to show the good performance of EFM in seismic modeling.

An approximation to the P-wave reflection coefficient for amplitude variation with long-offset seismic data

In recent years, long-offset exploration has been widely used, especially on marine seismic surveys. Conventional AVO analysis is insufficient for long-offset seismic data. To widen the application range of AVO analysis, we present a new P-wave reflection coefficient approximation applicable to long-offset data. Our result is similar to the well known Shuey formula which can be treated as an approximation to our results for short-offset seismic data.

Improving signal to noise ratio of seismic profiles using an image processing technique

This paper introduces an image processing technique into seismic data processing as a noise attenuation technology. The image separation of the seismic profile is obtained by using grating operators based on different time dips and a set of relative single dip profiles is obtained. A high signal to noise ratio profile can be obtained during reconstruction by statistical weighting. With further processing analysis and geological study, a high signal to noise profile that can meet geological requirements can be produced. The real data examples show that the signal to noise ratio of the porfile is greatly improved, the resolution of the profile is maintained, and the fault terminations are much clearer after using the image processing method.

Beamforming with the generalized sidelobe canceller for coherent noise attenuation in 3D seismic data

This paper presents a new approach for attenuating coherent noise in 3D seismic data. An adaptive beamforming with generalized sidelobe canceller (GSC) design methodology is utilized here as a general form of linearly constrained adaptive beamforming structure. It consists of a fixed beamformer, and a signal-blocking matrix in front of an unconstrained adaptive beamformer. Considerationf of the complexity of the geometry for 3D seismic survey, the 3D beamforming with GSC technique is developed with two key points: (1) sorting along azimuth sections to simplify the relationship between traveltime and offset from 3D to 2D, and (2) dynamic binning scheme to avoid the possible poor folding in some azimuth sections. Both simulation result and real data example show that the newly developed 3D beamforming with GSC yields more credible results at a relative low cost, sufficient stability and good resolution.