The laboratory and field experiments of [1, 2] showed the possibility of using a high-frequency electromagnetic (EM) field for deep and intense heating of a productive bed by heat sources distributed over the volume. The heat sources occur during interaction of a high-frequency EM radiation with the medium and are caused by conversion of part of energy of the propagating EM waves to heat. When a hydrate-containing rock is heated to the temperature of thermal decomposition of the gas hydrate, the latter can dissociate to the gas and water. Owing to the heat sources distributed over the volume, the phase transition can also occur in the absence of a temperature gradient. In this case, vast zones of phase transition can occur in which the gas hydrate decomposition temperature is attained and the EM field energy is expended on its dissociation.In [3][4][5], the Stefan problem was used as a mathematical model for the mathematical description of processes that occur in a heated medium and are accompanied by phase transitions (melting and decomposition). However, the assumption that phase transitions proceed on a geometrical surface (a front of zero thickness) is applicable only in the case where the width of the phase-transition zone is much smaller than the length of the EM waves radiated into the bed [3]. In addition, the width of the phase-transition zone should be much smaller than the characteristic dimension of the problem, for example, the characteristic length of the zone in which the EM radiation is absorbed by the medium. These conditions are satisfied for small times of heating. It has been shown [5] that, as the productive bed is heated by the EM field, the width of the phase-transition zone increases rapidly and, at some value of the width, the use of the Stefan mathematical model gives a distorted picture of real processes.The expression used in [3][4][5] for the density of heat sources distributed near the EM-wave radiator gives a value that is more than 2 times larger than the real value calculated from the exact solution expressed in terms of Hankel functions.In this connection, it is necessary to use a phase-transition zone of finite width in the mathematical model and obtain new expressions for the distribution of heat sources.1. System of Equations Describing the Thermodynamics of Gas Hydrate Decomposition under the Action of a High-Frequency EM Field. We study the following problem. A hydrate-saturated rock is under a bed pressure at a temperature lower than the decomposition temperature of the gas hydrate at the given pressure. The pore space is initially filled with the gas and the gas hydrate.At the borehole bottom, a sufficiently powerful source of high-frequency EM waves is located opposite to the productive bed. As the EM waves propagate, their energy is converted to heat. Over a fairly large volume of the borehole bottom, the temperature increases, and, near the radiator, it reaches the gas hydrate decomposition temperature that corresponds to the bed pressure. A moving boundary (or an exte...

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Planning, conducting and interpreting production logging data of operating horizontal wells is a complicated problem. It is accounted for by special aspects of thermo-hydrodynamic processes taking place under the conditions of a complex wellbore trajectory with uprise, horizontal and topdown sections that affect the distribution of phasal velocities and position of interphase boundary. There are favourable conditions for countercurrent flow to be formed in the uprise sections which distorts the readings of a flowmeter and forms atypical distribution of temperature field in the flow. It is impossible to take into account complex influence of these factors using only deduction and gained experience. Thus, it is essential to apply mathematical modeling when interpreting thermal hydrodynamic data of operating horizontal wells. Mathematical models for calculating holdups, velocities, temperature distribution of cocurrent and countercurrent oil-water flow are considered in present paper. The results of calculation and their analysis are presented in the work, the results of well surveys are being discussed.

Today, number of fracturing operations (fracturing) is increasing every year due to the development of low-permeability formations classified as hard-to-recover formations. The actual task is to determine parameters of fracture obtained in order to confirm the planned design, toimprove technology of fracturing fluid injection and proppant, toprevent premature watering and to frac non-target reservoirs. The fracture properties do not remain constant over time: under the influence of rock pressure, the proppant is compressed and destroyedandduring production part of proppant is washed out of fracture. Therefore, it is also important to monitor the change of fracture parameters over time. Technologies are known to determine the fracture parameters [16, 17]. Anywork aiming at developping accessible technologies with high level informativeness is relevant: Temperature transient ananlysis is one of them. Thermometry method is actively used in borehole geophysics. Unlike well tests (hydrodynamic studies), thermometry allows individual characteristics of each formation (inflow intervals) to be obtained in case of a multi-layer system. Thefield results and theoretical studies have shown that temperature is sensitive to the presence of fracture: by means of temperature measurements in the well, the fracture height is determined reliably now. An important task is to determine thefracture geometry - length, width, azimuth direction. The complexity of this problem solutionis due tothe fact that thermohydrodynamic processes in reservoir – fracture systemhas not been yet sufficiently studied. Therefore, theoretical studies are needed to study the effect of fracture on temperature and pressure fields in reservoir. In the presented work the problem is solved with help of mathematical modeling:analytical solutions are obtained and numerical model is developed. The results of multivariate calculations and their comparison with field data of temperature recovery in wellbore are presented.