Methods of suppressing free thermal convection in water-filled wells during temperature research

Тemperature measurements in boreholes are widely used in oil and gas geophysics, hydrogeology, geoecology, geocryology, and in the operation of hydrothermal resources. The number of applications of borehole temperature data is continuously growing. Requirement for temperature measurement accuracy is also growing. However, increasing the accuracy is limitedby free thermal convection phenomenon (FTC). It occurs under a positive temperature gradient and causes temperature noise, the level of which may exceed the useful signal. It was believed for a long time that the FTC currentsare organized as a vertical sequence of convective cells having a certain vertical dimension.Existing methods of FTC suppressing by horizontal discsare based on these ideas.Theoretical and experimental studies conducted by the authors showed that these ideas are incorrect. FTC currents are organized as a rotating helical system of ascending and descending jets, not limited vertically.Under these conditions, the most efficient and technological way is dividing the borehole by vertical stripes of polymer film into separate segments.Another method of FTC suppressing uses spherical hydrogel granules. The test results of the developed devices in a real borehole are described. Using of these devices allows to reduce the temperature noise by 16-20 times (from 0.025 - 0.044 K to 0.002 - 0.003 K).