High-viscosity oil is produced using electric bottom-hole heater – the device located in the bottom hole of the well below the pump suspension. This device allows for increasing the oil temperature thus decreasing its viscosity resulting in reducing the load on the electric submersible pump, for which there is a critical maximum of viscosity of the pumped fluid. Breaching this limit may result in the equipment failure and stopping of oil production.
To prevent this risk the oil producing companies use mathematical models allowing for determining the temperature distributions on the walls of the tubing and to define the location of potential accumulation of resins and paraffins. However, such models, as a rule, do not allow for studying the flow of oil through the perforation holes assuring hydrodynamic connection of reservoir with the well.
The new 3D model from the scientists of Perm Polytechnical University allows for removal of this limitation. It describes the transferring of heat and oil in the well and takes into account the area with the perforated tube. The researchers identified that oil has the highest velocity close to the perforated holes by the heater and the pump, and the lowest viscosity in the centre of the flow.
The calculations allowed for defining the required length of the heater sufficient for stable pumping of the fluid. The researchers compared several heaters of different capacity and length maintaining the same temperature (122 degrees Celsius). The experiments demonstrated that oil is heated faster by the device of 1 m length in the section between zero and two metres, because the specific capacity (energy – mass/volume ratio) of such heater exceeds the specific capacity of the devices of 3 and 5 metres length.
“We identified that using the heater with the highest capacity in the perforated well allows for increasing the oil temperature at the electric submersible pump suction up to 60°С, and for decreasing the viscosity down to 0.7 Pa•s. This is more than 14 times below the initial oil viscosity. Our model allowed for detailed description of the nature of the flow and heat exchange in the well section with low productivity and high-viscosity oil”, Perm Polytechnical University is citing Nikita Kostarev, candidate of engineering sciences and one of the researchers.
