FEATURES OF 3D RAY TRACING FOR MEDIA WITH COMPLEX GEOMETRY OF INTERNAL BOUNDARIES IN PRESENCE OF WEDGEDING-OUT OF LAYERS

Previously an original method for ray tracing in 3D environments with a complex internal boundary geometry was proposed.  In this article there was proposed a new modification of this method to enable operation in conditions of bed pinching out.  To eliminate the problems arising from the use of the ordinary algorithm, the velocity model is additionally defined in such  a way that the number of layers along the strike shall not change. Therewith, on some particular areas on the strike the  layers may have have a «small thickness», the values thereof being determined by the order of smallness. Changes have  been made to the 3D bisection algorithm, and the area of the iterative search for the refraction point has been reduced to  the value determined by the locality parameter. The efficiency of the method is proven by the results of numerical  simulation. The developed method is necessary for exact tie of sources of radiated emission in the course of seismological  and seismic surveys performed, as well as for work performed on mining fields

Experimental study of mechanoelectric transformations in low saturated rocks

The results of study of the electrical response of dry and slightly saturated with salted water (NaCl) or kerosene cores of Berea sandstone to acoustic effect in the frequency range of 0.5–10 kHz are presented herein. A strong lateral inhomogeneity by saturation was created during the experiments. The electrical response is sensitive to the addition of all types of fluid in the rock samples. At the same time, the reaction to the addition of highly concentrated salt solution in the samples is weak, while the reaction to the addition of weak concentrated salt solution and kerosene is strong. A high correlation is observed between the shape of the electrical response spectra of dry and damped cores, up to 0.9. For kerosene, the shape of the spectrum varies greatly, the rank correlation coefficient of the shape of the spectra is 0.3. The fact of a significant increase in electrical response on addition of non-polar fluid (kerosene) to the core is beyond the theoretical framework and may be associated with the creation of strong lateral petrophysical heterogeneity by saturation. The strong sensitivity of the amplitude of the electroseismic response of rocks to very weak but non-homogeneous saturation is interesting for the development of remote methods for determination of the type of fluid saturation of rocks, when searching for minerals and for the development of the methods for prediction of geophysical catastrophes

RESEARCH OF MECHANOELECTRIC TRANSFORMATIONS IN ROCK WITH A SMALL DEGREE OF FLUID SATURATION

The paper describes an experimental plant and data processing technique for investigations of acoustoelectric transformations in rock samples with varying degrees of moistening. The results of investigations are presented for dry and moistened with kerosene core of Berea Grey sandstone under acoustic effect produced by linearly frequencymodulated signal in 0,7–10 kHz band. The was discovered a strong effect nonlinearity expressing itself in the second and third harmonics emerging, and an increase in the amplitude of the response of the electric signal. In the lower frequency band the amplitude of the second harmonic of the electric field intensity oscillations is comparable with the amplitude of the first one and can even exceed it. With the dropwise addition of kerosene, the power of the electrical signal varies at many times with a strong change in the shape of the signal spectrum. Therewith the shape of the acoustic signal spectrum is practically unchanged. The strong sensitivity of the coefficient of acoustoelectric transformation of rocks to moistening, which significantly changes the amplitude and phase of the response, is interesting from the point of view of developing remote methods for identifying the type of fluid saturation of rocks and methods for predicting geophysical catastrophes