Temperature Variation Across The Wellbore in SAGD Producer

Abstract Temperature measurements are widely used for SAGD real time monitoring. Nevertheless field DTS data demonstrates presence of the strong temperature variations across the SAGD producers and therefore introduce uncertainty in interpretation of the temperature data. This work is devoted to the numerical analysis of the generation mechanism for temperature variation across producer, estimation of the magnitude of such temperature variations. Methodology for numerical evaluation of temperature variation across the SAGD producer wellbore was developed. The simulated temperature variations were found to be in good agreement with the field data. Introduction Application of the fiber optic distributed temperature sensors (DTS) in steam-assisted gravity drainage (SAGD) process of heavy oil recovery has increased significantly during last years. This technology is proven as source of valuable information for real-time monitoring of steam trap and production control. Some field temperature data shows presence of the spatial temperature variations across horizontal SAGD producer. Observed temperature variations (that are believed to be related to temperature difference between the upper and lower zones of the wellbore) exceed 20 deg C that can create uncertainty in estimation of local temperature and therefore decrease value of the temperature measurements, lead to the problems with subcool control in particular producer zones. The temperature variations appears as parts of the DTS profile with temperature spatial oscillations with nearly constant step about several meters in order of magnitude and with amplitude from 10 up to 30 C.1,2 Because the same DTS installations are providing almost smooth temperature profiles (with temperature variation within 1C) for the other sections of the well significant temperature variations should be attributed to the specific features of heat transfer in that particular wellbore sections and could be used as additional source of the information about the flow in producer. In all field cases 1,2 significant DTS data oscillations are seemed to be related to significant temperature variation across wellbore that became visible due to specific completion features and details of the DTS cable deployment (centralizers, tubing etc.). This paper focuses on numerical investigation of the generation mechanism for these cross-sectional temperature gradients and evaluation of its value within the SAGD producer. The study was inspired by the analysis of Deer Creek field case data presented in the paper2. Numerical Model Analysis of the problem is based on the results of the detailed numerical simulation of the coupled multidimensional problem of multiphase flows in reservoir and SAGD producer. 2D SAGD numerical simulations were done using commercial reservoir simulator and provided information on the details of the inflow to the production well and temperature, pressure and fluid saturation around producer. These data were used as initial and boundary conditions for detailed 3D simulations of the multiphase flows in vicinity of the producer and within the producer wellbore performed using industrial Computational Fluid Dynamics (CFD) code FLUENT. In present study regular production without steam breakthrough into the producer was considered.