THERMAL FIELD IN THE WELL DURING INDUCTION HEATING OF THE CASING UNDER CONDITIONS OF LOW FLOW VELOCITY

Abstract

Relevance. One of the promising methods of production logging of wells is active thermometry. The research technology of this method includes local induction heating of a metal casing, registration and analysis of temperature changes in the wellbore. As a result of heat exchange between the fluid moving in the well and the column, a thermal mark is created, which is recorded by temperature sensors located in the column along the path of the fluid movement. Monitoring the movement of heat marks allows solving a number of important practical tasks, such as determining the volume fluid flow rate in the wellbore, estimating the flow rate of the behind-the-casing flow. At a low flow rate, the heating of the column can lead to significant temperature gradients in the liquid, which causes the occurrence of natural thermal convection. In this regard, the study of thermal processes in wells with heating with natural convection turned on is relevant. Object: a production well in which studies are carried out using the method of active thermometry using local induction heating of the casing. Purpose of the research is to study the features of temperature field formation in the well during induction heating of the casing, taking into account natural thermal convection at a low flow rate in the wellbore. Methods: numerical simulation in the Ansys Fluent software package (ANSYS Academic Research CFD license, agreement with Bashkir State University dated 06/15/2020). Results. It was found that heating the column and the liquid near its surface reaches more than 12 and 5 K, respectively, which contributes to an increase in the local velocity of the liquid due to the influence of natural thermal convection. Above the heating interval, a repeating flow structure is observed in the liquid, corresponding to the formation of convection cells. Curves of fluid temperature dynamics over time at different radial distances from the column wall and different heights relative to the heating interval are constructed, the linear velocity of the fluid flow is estimated by the time of arrival of the heat mark. It is established that the calculated velocity of the liquid, determined by the velocity of the heat mark, increases by an amount of 6 % or more relative to the velocity of the laminar upward flow in the absence of the influence of natural thermal convection. It is shown that measuring the temperature in the central part of the flow makes it possible to more accurately estimate the flow rate of the liquid in the column, since in the wall areas the local velocity of the liquid increases due to natural convective flows.

Keywords

• active thermometry
• temperature marks method
• natural thermal convection
• flow velocity
• ansys fluent
• cfd simulation