Improvement Heavy Oil Transportation IN Pipelines ( laboratory study )

Since from the past, drag has been identified as the main reason for the loss of energy in pipelines and other similar transportation channels. The contribution of this drag is due to mainly viscous of the flow as well as friction against the pipe walls. These energy losses can be identified through pressure drop, which will results in more pumping power consumption. 
Due to their very high viscosity heavy oil cannot be transported as such in pipelines and required additional treatments [1]. 
This work studied flow increase (%FI) in  heavy oil at different flow rates (2 to 10 m3/hr) in two pipes (0.0381 m & 0.0508 m) ID. By using different additives (toluene and naphtha) with different concentrations (2, 4, 6, 8 and 10) %wt at 27ᵒC. 
      The results of this study showed Increasing values of FI % and Maximum Dr% of 40.48% and 37.03 % were obtained using heavy oil containing 10% wt of naphtha flowing in pipes of 0.0508 and 0.0381 m I.D. at 27°C respectively. 
Increasing values of %Dr with increasing of Reynolds number, fluid velocity and additive concentration, the used additives (toluene and naphtha) reduce the high viscosity of used heavy oil, and naphtha is more efficient as viscosity reducer than toluene. 
All these results show treatment heavy oil and improvement their transport in pipelines.


Introduction:
Drag reduction is a phenomenon in which the friction of a liquid flowing in a duct in turbulent flow is decreased by using small amount of additives. This is beneficial because it can decrease pumping energy requirements. Some current applications where drag reduction has been applied include oil transmission pipelines, district heating and cooling systems. Different types of additives can be used in these systems and include surfactants, fibers, aluminum disoaps, and polymers. Drag reducing additives are effective because they reduce the turbulent friction of a solution. These results will decrease the pressure drop across a length of conduit and likewise reduce the energy required to transport the liquid [2].

Drag reduction by using surfactants
Abdul-Hakeem tested different types of surfactants, three anionic surfactants plus one non-ionic surfactant as drag reducers in turbulent pipe flow of Iraqi crude oil within three pipe diameters of 0.5, 1, and 3 inch I.D. The investigator concluded that the percentage drag reduction (%DR) increases by increasing the surfactant concentration (within certain limits), solution flow rate and pipe diameter. Maximum percentage drag reduction of 56.5% was achieved at concentration of 200 ppm SDBS surfactant. Finally, the drag reducing mechanism was explained by the interaction of surfactant micelles with the crude oil, which allows the turbulence to be suppressed [3].

Drag reduction by using polymers
Motier used polymeric drag reducing agents to facilitate the pipeline transportation of crude oil and some refinery products (reducing the frictional loss associated with turbulent flow of liquids). Motier obtained the best performance with gasoline and fuel oil in his experiments.
The great effectiveness has been found in the low viscosity Kirkuk crude oil. The variability in performance was a function of the viscosity of crude [4].Shao and Lin studied the mechanism of drag reduction by polymer (polyacrylamide) additives. The researchers concluded that the visualization of mixing layer shows that the addition of polymer will enhance coherent structure. The measurements of the turbulent intensities and Reynolds stresses by LDA show that polymer additives do not simply suppress the turbulent fluctuation as they expected. In E202 pipe flow, the axial turbulence intensity is increased while the radial turbulence intensity is decreased. This means that the turbulence structures are changed rather than suppressed [5].

Viscosity reduction
Blending with a less-viscous hydrocarbon such as condensate, naphtha, kerosene or light crudes its called dilution. However ,in order to attain acceptable limits for transport, a fraction as high as 30% of diluents by volume is necessary and implies large pipeline capacity. Problems may also arise with regard to diluents availability [6].
Dilution could be a solution for heavy oil, but requires a large investment for the installation of an additional return pipeline.
One of the modern techniques in drag reduction is by the addition of different 3. To study the influence of solvents that reduced the viscosity of heavy oil with significance to their functions in the drag reduction in pipelines.

Experimental work:
Description of circulating flow loop system the description of main parts of the flow system as shown in figure (1). It represents the flow system apparatus used in the present work, which consist of reservoir tank of solution, pump, flow meter, pipes, valves, pressure transmitter, digital screen, chiller and digital thermometers

Solvents
Toluene and naphtha were used as drag reducing agents and to dilute the viscosity with concentration 2, 4, 6, 8 and 10% by weight. Solvents were provided by Al-Doura refinery.
Experimental procedure 1. The reservoir was filled with 75 liter of corresponding fluid heavy oil.      4. The solvents (toluene and naphtha) were found to dilute the high viscosity when used with heavy oil.
5. The drag reduction occurs because of the interaction of the additives with heavy oil due to increasing the intermolecular distance within the oil and decreases the viscosity and density.
6. The solvents (toluene and naphtha) change the physical properties of present used heavy oil, while the viscosity was reduced which indicated that we treated high viscosity and improved their transport in pipelines.