Generation of the low-frequency branch of acoustic emission in affected rocks

As follows from data analysis of physical modeling, the reaction of acoustic background oscillations to an external impact is well-defined under triaxial loading of a dry sandstone core in the low-frequency range (1–100 Hz). This phenomenon is explained by the generation of a low-frequency constituent of acoustic emission. A high correlation of oscillation dynamics (Klimontovich S entropy) is observed at frequencies of tens of hertz and tens of kilohertz in the absence of such a correlation in the intermediate frequency range; a synchronous increase in the oscillation level is also observed at low and high frequencies.     

A Thermodynamic Indicator for Remote Assessment of the Productivity of a Hydrocarbon Reservoir

Doklady Earth Sciences - The local productivity of a reservoir on the territory of a hydrocarbon field was assessed remotely using thermodynamic indicator of the state of the geological...     

Ray Tracing Methods in Seismic Emission Tomography

Highly efficient approximate ray tracing techniques which can be used in seismic emission tomography and in other methods requiring a large number of raypaths are described. The techniques are applicable for the gradient and plane-layered velocity sections of the medium and for the models with a complicated geometry of contrasting boundaries. The empirical results obtained with the use of the discussed ray tracing technologies and seismic emission tomography results, as well as the results of numerical modeling, are presented.     

A method for localizing seismic sources whose signals are separated by an order of difference from the background noise

Doklady Earth Sciences -     

Effect of a Shift in Diurnal Geomagnetic Variation on the Activity and Sensitivity of Digestive Glycosidases in Roach Underyearlings to Heavy Metals

Izvestiya, Atmospheric and Oceanic Physics - The effect of temporal shifts in diurnal geomagnetic variation with 6- and 12-h intervals relative to the day–night cycle on the activity of...     

Elimination of high-amplitude noise during passive monitoring of hydrocarbon deposits by the emission tomography method

Emission tomography used in passive seismic monitoring of hydrocarbon deposits enables regular inspection of development of hydraulic fracturing and relaxation processes in volumes of fracturing, tracing of fluid migration paths, redistribution of stresses due to field development accompanied by seismic emission from volumes of structural defects and stress concentration, and localization of fractured and faulted structures from emission and scattering data. Intensive man-made seismic noise in the areas of oil field development produces a strong screening effect in identification of weak deep seismic sources. On the basis of experiments with simulated and real data of surface seismic arrays in regions of oil deposits in Western Siberia (carried out in the framework of the passive monitoring program of the SYNAPSE Science Center), it is shown that the use of algorithms of adaptive optimal and rejection spatial filtering with the estimation of the spectral density matrix of multichannel observations in the framework of multivariate autoregressive-moving average modeling is effective for eliminating the influence of anthropogenic noise and revealing (in oil production areas) both deep seismic sources supposedly active in scattering regions of the lower part of the sedimentary cover and the crystalline basement. The projection of the scattering regions onto the horizontal plane correlates well with the position of faults in the area of in situ observations.     

New algorithms of emission tomography for passive seismic monitoring of a producing hydrocarbon deposit: Part II. Results of real data processing

Two new algorithms of seismic emission tomography and the results of their numerical testing are presented. The algorithms allow eliminating of the screening effect caused by spatially correlated noise, and imaging of deep weak sources. Both algorithms invoke spatial filters, calculated on the basis of singular decomposition of the spectral matrix of the wave field. The key parameter of such a filter is the number of eigenvectors of the spectral matrix, which must be rejected in the process of seismic emission imaging in order to eliminate the screening effect. Consecutive increasing in the number of rejected eigenvectors enables imaging of ever weaker seismic sources.     

New algorithms of emission tomography for passive seismic monitoring of a producing hydrocarbon deposit: Part I. Algorithms of processing and numerical simulation

Two new algorithms of seismic emission tomography and the results of their numerical testing are presented. The algorithms allow eliminating of the screening effect caused by spatially correlated noise, and imaging of deep weak sources. Both algorithms invoke spatial filters, calculated on the basis of singular decomposition of the spectral matrix of the wave field. The key parameter of such a filter is the number of eigenvectors of the spectral matrix, which must be rejected in the process of seismic emission imaging in order to eliminate the screening effect. Consecutive increasing in the number of rejected eigenvectors enables imaging of ever weaker seismic sources.