articles

 

A method to attenuate the random noise and retain the signal on the seismic data after transformation from the time spatial (t-x) into the frequency spatial (f-x) domain is considered. This algorithm is usually called “f-x deconvolution”. It has got its specific features and this paper is devoted to their analysis. The theoretical background is given, some modifications are introduced, and methodological recommendations are proposed. Synthetic and real data examples are given.

We propose a new accurate method for the simulation of full seismic wave fields and primary spherical waves. It is based on special analytical transformations. In this method, grid approaches are not employed, end there are no restrictions on parameters of media models, frequency and offset data. Also, the wave method for multiple suppression for which the knowledge of a depth-velocity medium model is not required has been developed. The convergence and stability of this method for arbitrary 3D plane-layered media are theoretically and numerically proved. Industrial time sections that were obtained with ProMAX and Geovecteur were completely processed. The results obtained have drastically decreased the level of multiple waves without amplitude distortion of usable reflections.

Here we investigate development of stacking formula for common reflection surface (CRS) and multifocusing (MF) methods in the context of approximation of two dimensional time field. In such manner we are presenting here traditional deviation of stacking formula CRS on the basis of expansion in Tailor series. We newly developed formula for MF through the geometrical approach. Here proven the fact that stacking formula for MF in case of media with smooth interface is an approximation of time field with second order of accuracy in close proximity of stacking point and the same truth for CRS as well. Here we introduce error correction for MF stacking formula that generally developed through incident and reflected wave fronts. Correct method of determination of wave front for pair of source and receiver is presented here. We resumed here that approximation character of stacking formula for MF & CRS not allows to apprise accuracy of kinetic parameters (α, RNIP, RN) and rates of fold and offset as well.

Seismic monitoring of a hydrocarbon reservoir during production provides an opportunity to control mechanical characteristics of the productive formation and to predict its oil and gas saturation and pore pressure. Present-day level of seismic technologies allows to register multicomponent data using both surface and borehole seismic surveys and to achieve good repeatability of the experiments. Data registration in boreholes has a number of advantages comparing to surface seismic. For example it allows to fix sources and receivers positions, and also it provides a significantly lower level of noise. Moreover, the ability to place sources and receivers at the level of the target layer (productive formation) decreases the influence of the near-surface and reduces distance of waves' propagation. The disadvantage of such system is a small number of the sources and receivers, which can be placed in the boreholes. Therefore, an estimation of the resolution ability and the quality of the expected results in the presence of realistic noise-level are of great importance. The presented in the work  analysis of the resolution ability and informativity shows a principal possibility to use the borehole acquisition systems for monitoring the variability of the elastic parameters in the target area in the presence of realistic noise-level.

Computer-aided structural modeling techniques demonstrate that the current geological and geophysical workflows could be improved with the help of paleotectonic analysis that will refine the quality control of seismic data interpretation, incorporate accurate cross section balancing and validation, create tectonic evolution models that will ultimately reveal new structural and tectonic traps. The paper presents Paradigm™GeoSec® package that has demonstrated high efficiency and accuracy in the interpretation of 2D seismic sections along regional profiles from the northern part of Taimyr Peninsula, Northern Russia.

Prestack simultaneous inversion was performed on synthetic and measured seismic data to appraise the influence of several factors to estimation of P- and S- wave velocity and especially density. The measured data from Western Siberia were used to generate the synthetic data. Analysis on synthetic data indicates that even in the ideal case of noise-free data we have to carry on about angle range. For accurate density estimation it is necessary to use far-angle data (more than 30 degree). Lastly 5 - 50% random noise was added to the synthetic data, and misfits between inversion results and model data were analyzed. Finally inversion was performed on measured data.

This article highlights realization of total seismic exploration in areas of complex hydrography. The proposed technique combines advantages of seismic acquisition when energy sources (airguns) are located on rivers, while receivers are distributed ar eally (total seismic).
A test acquisition in real conditions showed high effectiveness of total seismic. It allows a substantial cost decrease. In some areas, the total seismic is the only 3D acquisition method because dynamite shots are prohibited in water protection zones, while vibroseis sources will not be in a position to implement regular areal acquisition systems on land because of passage obstructions and the need to cross waterways and because of organizational difficulties for seismic operations in water protection areas. Another advantage of the total seismic is its ability to be deployed in West Siberia and East Siberia in summer time when seismic acquisition is practically not run there.

The problem of upper part velocity heterogeneity is studied. Heterogenity is represented by a zones of low or high velocity in the underlying strata, in the upper part of which stable refracted wave is formed. It is shown that  the joint interpretation of vertical borehole source times and the refracted wave travel-time curve parameters lead to the unique  solution to problem of static corrections a priori calculation .

Questions of looking up and mapping of petroperspective objects by means of seismic works 2D, spent within the limits of the uniform all up project on overland leases, in transit zones and on water areas of large water storages are esteemed. The concrete seismogeological situation which has predetermined necessity of sharing various by the nature of sources of stimulation of elastic vibrations is described: vibrators -  at working off of the open flat leases of the floor space, detonatings in holes  - at passing remote dence forest boggy territories, transit zones, shoal leases of water storages, and, at last, pneumosources -  at conducting fluvial seismic survey. The problems linked to data in a uniform massive of source field data are designated, and results of all up treating and the interpretation, allowed to open in the Perm Prikamye oil object of the big importance.

Problems of interpretation of a seismic data on the basis of geophysical researches within the limits of territory of the North-East Sakhalin are given in this paper.

In our days prospecting seismology faces problems in studying of difficult reservoirs and forecasting of their filtrational-capacitor properties in cross-well space. However not enough at tention is frequently given to factors deforming dynamic characteristics of a wave field. In northern areas of Western Siberia this factors are developed by permafrost zones. Researches of influence of anomalies of the top part of a subsurface on seismic recording dynamic characteristics are carried out in article on an example of the North Gubkinsky field. It is proved that the correction for near-surface heterogeneities improves dynamic characteristics and allows to spend forecast of filtrational-capacitor properties of collectors.