The steamflooding of deep reservoirs requires the use of insulated tubing to minimize heat losses and maintain high-quality steam at the sandface. In order to evaluate the effectiveness of tubing used, techniques are needed to measure the heat loss in the wellbore and calculate the thermal conductivity of the insulation.
This paper presents the results of tubing analysis in a well of 4250 ft depth using pressure-temperature survey data. The problem of determining the bottom-hole steam quality under normal operating conditions was overcome by setting the inlet quality at a level estimated to result in zero quality at the sandface. This allowed the calculation of bottom-hole enthalpy and total heat loss using pressure and temperature measurements. The performance of the insulated tubing was evaluated by adjusting variables in a wellbore simulator to obtain a match of the experimental data recorded at several elevations.
Results of the test concluded the heat loss in the injection well was 130% higher than predicted using anticipated tubing properties. The heat loss was uniform through the tubing, and resulted from poor insulation performance. The simulation results eliminated the possibility of heat loss due to refluxing in the tubing annulus.