Effects of wax deposition on the flow field of coiled tubing with built-in cable

In this paper, the effects of the distribution and thickness of wax deposition on the flow velocity and pressure of crude oil were investigated so as to deal with the energy loss and potential safety hazards caused by the wax deposition on pipeline walls in the process of crude oil transportation. The three-dimensional numerical simulation was conducted on the flow field of coiled tubing with built-in cable in a vertical well with/without wax by using the computational fluid dynamics software Fluent in the simplified wax deposition model. It is shown that the crude oil flows slowly along the axial line of the wellbore after it enters the pipeline with wax deposition. The crude oil flow locally shrinks or expands correspondingly in the vicinity of the wax-starting position and the wax-ending position. Due to the paraffin layer, the flow cross section is no longer circular and distribution of the flow velocity cloud chart is also separated from the axial symmetry. The peak flow velocity appears in the flow cross section without wax deposition and increases significantly. The radial velocity profile is parabolic whether wax is deposited or not. The pressure at the flow cross section of the wellbore with wax deposition is equal to that without wax deposition and they decrease from the inlet to the outlet. The wellbore with wax deposition suffers not only the energy loss along the course, but also the local energy loss, so its energy loss is greater.