Projektowanie metodyki prac sejsmicznych w Lubelskim Zagłębiu Węglowym na podstawie modelowania teoretycznego pola falowego
Abstract
DESIGNING METHODS OF SEISMIC SURVEYS IN THE LUBLIN COAL BASIN
Summary
The Lublin region is characterized by complex seismogeological conditions. This is mainly due to occurrence of numerous thin layers highly differing in velocities and density in the Carboniferous-section.
In accordance with the theory of propagation of waves in thin-layered media, coefficients of reflection and penetration are the function of frequency of predominating elastic waves. This makes the range of frequency the basic methodical parameter, determining resolution power of seismic record. This is of special importance for surveys on black coal deposits, the major tasks of which include mapping of economic coal seams, location of discontinuity zones, etc.
The influence of frequency on resolution power of seismic record may be traced by modeling theoretical wave image by e.g. synthetic seismogram method. This makes possible definition of the frequency range, necessary for solving the above geological problems.
The model studies presented here (see the enclosed synthetic seismograms calculated for the drilling Rejowiec IG-2), aimed at mapping structural pattern in the Lublin Coal Basin, showed that frequencies used in structural seismics (of the order of 30- 50 Hz) are sufficient for that purpose. In order to increase accuracy of recognition of the rock massif, especially for obtaining data on structure of coal seams, it appears necessary to use higher frequencies (of the order of 80-120 Hz). This involves essential changes in methods of surveys in the case of field works, processing of the obtained materiał as well as interpretation, i.e. introduction of so called coal seismics.
Summary
The Lublin region is characterized by complex seismogeological conditions. This is mainly due to occurrence of numerous thin layers highly differing in velocities and density in the Carboniferous-section.
In accordance with the theory of propagation of waves in thin-layered media, coefficients of reflection and penetration are the function of frequency of predominating elastic waves. This makes the range of frequency the basic methodical parameter, determining resolution power of seismic record. This is of special importance for surveys on black coal deposits, the major tasks of which include mapping of economic coal seams, location of discontinuity zones, etc.
The influence of frequency on resolution power of seismic record may be traced by modeling theoretical wave image by e.g. synthetic seismogram method. This makes possible definition of the frequency range, necessary for solving the above geological problems.
The model studies presented here (see the enclosed synthetic seismograms calculated for the drilling Rejowiec IG-2), aimed at mapping structural pattern in the Lublin Coal Basin, showed that frequencies used in structural seismics (of the order of 30- 50 Hz) are sufficient for that purpose. In order to increase accuracy of recognition of the rock massif, especially for obtaining data on structure of coal seams, it appears necessary to use higher frequencies (of the order of 80-120 Hz). This involves essential changes in methods of surveys in the case of field works, processing of the obtained materiał as well as interpretation, i.e. introduction of so called coal seismics.