Experimental capabilities of seismic emission tomography for solving the problems of searching and exploration of deep hydrocarbon accumulations

The standard seismic prospecting has been designed to investigate thin layering at shallow depths. At depths more than 4 km the rocks are significantly compacted, change their properties and it is often impossible to trace clear horizons by reflected waves. In the crystalline basement and lower horizons of the sedimentary cover the block structure of rocks is clearly manifested. Taking this into account geological models should be developed and other predictive indicators should be used when searching for hydrocarbon accumulations. For the study of great depths more informative seismic methods are emission and transmission tomography which have been developed in detail in seismology. This article discusses prognostic indicators different from seismic prospecting and presents experimental results confirming the success of emission tomography in their detection using the example of field studies at developed hydrocarbon deposit and other geophysical objects. The range of working depths of research covers the entire crust of the Earth including the crust-mantle transition zone. Keywords: seismic emission; emission tomography; rocks; hydrocarbon deposits.

INTEGRATION POTENTIAL OF MICROSEISMIC ANALYSIS AND GEOPHYSICAL METHODS. GAS CONDENSATE FIELD CASE STUDY

This study is devoted to an analysis of microseisms registered on gas-condensate field area. Presence of seismic emission effect on a part of the area is demonstrated. A microseismic anomaly is outlined in NW part of the area and proves correct by 3 seismic CDP profiles and interpreted as a reservoir. The results of the special processing was compared to the results of a set of other geophysical methods. Correlation between the found anomaly and an anomaly found with aerogamma-specrtometry is shown. The results can be used in an integrated interpretation of geophysical data for oil and gas reservoirs of both structural as nonstructural types.

Research of the microseismicity location algorithm

In this paper, we propose the algorithm for locating microseismic events by the method of directed summation of energy envelopes over a network of stations. The algorithm is based on a back projection technology, which allows visualizing the intensity of seismic emission by layer. A comparative stability and robustness analysis of the proposed method with the method using the semblance is carried out.

On the seismic emission in sunspots associated with Lorentz force changes accompanying major solar flares

ABSTRACT Solar flares are known to generate seismic waves in the Sun. We present a detailed analysis of seismic emission in sunspots accompanying M- and X-class solar flares. For this purpose, we have used high-resolution Dopplergrams and line-of-sight magnetograms at a cadence of 45 s, along with vector magnetograms at a cadence of 135 s obtained from Helioseismic and Magnetic Imager instrument aboard the Solar Dynamics Observatory space mission. In order to identify the location of flare ribbons and hard X-ray footpoints, we have also used Hα chromospheric intensity observations obtained from Global Oscillation Network Group instruments and hard X-ray images in 12–25 keV band from the Reuvan Ramaty High Energy Solar Spectroscopic Imager spacecraft. The fast Fourier transform technique is applied to construct the acoustic velocity power map in 2.5–4 mHz band for pre-flare, spanning flare, and post-flare epochs for the identification of seismic emission locations in the sunspots. In the power maps, we have selected only those locations which are away from the flare ribbons and hard X-ray footpoints. These regions are believed to be free from any flare related artefacts in the observational data. We have identified concentrated locations of acoustic power enhancements in sunspots accompanying major flares. Our investigation provides evidence that abrupt changes in the magnetic fields and associated impulsive changes in the Lorentz force could be the driving source for these seismic emissions in the sunspots during solar flares.

APPLICATION OF SANMCS TECHNOLOGY FOR MARINE SEISMIC DATA PROCESSING

The article presents the results of applying the technology of spectral analysis of microseisms to marine seismic data. The fundamental differences between the software-algorithmic and methodological aspects of the processing of marine and land seismic data are described. Correlation of microseismic spectrum anomalies in the range of 4–8 and 10–15 Hz with a known oil accumulation is shown; the correspondence of another 10–15 Hz spectrum anomaly with gas condensate accumulation was also found. The conclusion about the seismic emission nature of microseism anomalies has been substantiated. The development process of seismic emission in time is considered. It was found that for each local emission zone, the beginning of the process development may have its own time. The duration of the maximum emission level phase is from 0.5 to 0.75 s. The stability of processing results is shown; local anomalies of the microseismic spectrum are traced on several parallel receivers lines that are 100 m apart from each other.

BARENTS-EURO/ARCTIC

Continuous seismic monitoring of the Kola Peninsula and the Spitsbergen archipelago with adjacent water areas was carried out. Seismic events were recorded using digital equipment. Operational catalogs of earth-quakes were compiled. Great attention is paid to the improvement of systems for seismic and infrasonic monitoring. Seventeen seismic events with magnitudes from 0.8 to 2.8 which can be interpreted as tectonic earthquakes were recorded in the Baltic Shield area. The strongest earthquakes were recorded in the Arkhangelsk region (28.03.2013, M=2.9), in northern Norway (09.02.2013, MLрег=2.8), and in northern Finland (21.11.2013, MLрег=2.7). The maximum magnitude of the event in the Murmansk region was 2.3. The seismic activity in 2013 was the lowest over the last five-year period (from 2009 to 2013). The Spitsbergen archipelago was characterized by the smallest number of earthquakes in all ranges of magnitudes and by the smallest amount of released seismic energy for the five-year period from 2009 to 2013. The experimental research to monitor seismic and infrasonic emissions generated by glaciers was carried out using a seismic and infrasonic system installed before in the Spitsbergen archipelago. In particular, the seismic emission generated by the Isfjord glaciers has a strong seasonality. Activation is observed in the second half of summer and continues until the 20th of September. As a result of the studies, the possibility of remote monitoring of the destruction of glaciers by the seismic and infrasonic method was convincingly demonstrated