<p>A methodological approach to quantitatively assessing the flow rate of behind-the-casing flow based on wellbore thermometric studies is presented. The development of modern instrumental methods for recording wellbore temperature measurements creates the need to address the issue of behind-the-casing flow, one of the causes of high water cut in production wells. This paper considers the problem of fluid circulation from the bottom up from the underlying nonperforated formation to the bottom of the perforated interval in a vertical well. Analytical dependences for quasi-stationary temperature distributions along the wellbore of a production well are obtained. The dependence of thermogram distributions (shape, slope, and absolute values) on the flow rate of behind-the-casing flow during calorimetric mixing and convective heat transfer of wellbore fluid was established. When examining the thermal field with behind-the-casing flow, two types of problems were considered: with and without fluid movement along the column. Based on a series of simulated thermograms, interpretative features for identifying behind-thecasing circulation were demonstrated. The developed methodology was tested using real wellbore thermograms. Quantitative parameters of behind-the-casing flow were obtained: position in the wellbore, flow rate, and the proportion of behind-the-casing circulation.</p>