To solve problems of defining operating intervals and sources of water-cut in horizontal wells a complex of oilfield geophysical methods with a multisensor installation is used. One of the main and informative methods of surveying horizontal wells is temperature logging. A number of publications analyze possibilities of using thermal and hydrodynamic methods for horizontal well logging [1,2,3]. The method of ‘active thermal survey'  has been recently paid great attention to, it involves forming, analyzing the movement and disappearance of temperaturel marking. The following works are devoted to the use of temperature marking in the process of solving oilfield problems [5,6,7]. The perspectives of applying the method of temperature marking while estimating the flow characteristics are also recorded, especially in low rate wells. As a rule, horizontal wells are characterized by low local flow rates in the borehole, and well flowmetres do not always work properly. Therefore, analyzing the possibilities of using temperature marking in horizontal wells to determine the fluid-flow rate is an urgent problem.
As it is known, the borehole equipment goes down to the borehole of a horizontal well in one of the following ways: rigid cable, flexible pipes, bottom hole tractor, etc. [5,6]. In the final case while the bottom hole tractor is working, a certain amount of heat is being generated, i.e. a temperaturel mark is formed and then it disappears in the borehole of the horizontal well. So it is of interest to investigate heat anomalies caused by an operating tractor in the borehole of a horizontal well and to take this factor into account when interpreting the data of temperature and hydrodynamic logging. On the other hand, to analyse temperature distribution in the borehole of a horizontal well with heat sources is also important from the point of view of solving problems of defining flow characteristics, operating intervals, etc.
This work deals with specific features of temperature distributing in case of one-phase and multi-phase flows on the basis of mathematical simulation of thermal processes in the borehole of a horizontal well with a local heat source. Here fundamental equations of mass conservation, momentum conservation and the equation of heat inflow for two phases are presented. To describe heat exchange processes certain correlations for two-phase flows of gas and liquid, oil and water are used.
The article also describes peculiar features of forming a temperature field in the borehole with a moving heat source in the borehole of a horizontal well in case of one-phase and two-phase flows. It is shown that the presence of a heat source in case of two-phase flows causes the appearance of temperature fronts related to the movement of the two phases with different velocities. Sections corresponding to the intervals of oil or water inflows (operating intervals) are recorded as temperature anomalies against the operating heat source.
Practical data of forming temperature in the borehole of a horizontal well with the use of ‘a tractor' as a means of tools delivery are analyzed.