HYDRODYNAMIC METHODS FOR THE INVESTIGATION OF WELLS AND RESERVOIR

The analysis of literary sources in this study showed that in order to solve the problem of the pressure recovery curve during hydrodynamic probe of the reservoir in the case of its constant porosity a number of studies were dedicated to the nonstationary solution of the deterministic Darcy equation for an unlimited reservoir or on methods of empirical or semi-empirical modeling for static errors, which is associated with a nontrivial approximation of the asymptotic part of the pressure recovery curve.In this study, a new method for calculating the hydrodynamic parameters of an oil reservoir is proposed, taking into account all the information from the pressure recovery curve. In contrast to the existing methods, the proposed model of pressure versus time adequately describes the entire pressure recovery curve when the well is closed, which makes it possible to fully evaluate the hydrodynamic parameters of the reservoir.

Extremal charged Vaidya and its near horizon geometry

Recently [Formula: see text]-dimensional spherically symmetric charged Vaidya black hole solution has been constructed. We observe that this nonstationary solution admits extremal limit and study its near horizon geometry. We show that the symmetry of the near horizon geometry is [Formula: see text]. Our analysis shows that the theorems for the near horizon geometry of stationary extremal black holes, may be extended to nonstationary cases.

NONSTATIONARY STAGE OF QUASI‐CHERENKOV BEAM INSTABILITY IN PERIODICAL STRUCTURES

Analysis of nonstationary stage of quasi‐Cherenkov instability of electron beam in the case of two‐wave distributed feedback is carried out. Mathematical models and numerical methods of nonstationary quasi‐Cherenkov electron beam instability are proposed. Results of numerical experiments are proposed. Bifurcations of nonstationary solution are discussed. Straipsnyje analizuojama nestacionariosios fazes kvazi‐Cherenkovo elektronu spinduliuotes nestabilumas esant dvieju bangu saveikai su grižtamo ryšio pernešimu. Pasiūlyti šios elektronu spinduliuotes nestacionariosios fazes atveju matematiniai ir skaitiniai sprendimo metodai. Pateikti skaitinio eksperimento rezultatai. Aptartos nestacionariojo sprendinio bifurkacijos.

Cumulant Neglect Closure of Nonstationary Solutions of Stochastic System

The comparison of the exact nonstationary solution of stochastic dynamic system with the corresponding one obtained by the cumulant closure technique is presented in this paper. The solutions of linear system with colored noise will be considered.