WEATHERING EXPERIMENT ON SPILLED CRUDE OIL
USING A CIRCULATING WATER CHANNEL

Mr. Tsutomu Tsukihara
Koa Oil Co., Ltd. Japan[Introduction]
In order to determin the best suited recovery materials to be used during recovery of spilled oil , itis important to understand properties of the spilth. For that reason, We have constructed a small
circulating water channel, and carried out weathering experiment on spilt crude oils.
Further we studied the forming state of emulsified oil using electron microscope.
[Outline of water channel]
The water channel that we constructed for this experiment is an elliptic race track type. (figure 1)
This water channel can duplicate various types of waves by an attached wind tunnel, waves generator
and sea water circulator.

Figure 1.

Outline of circulating water channel

[Selection of type of crude oils]
The experiment is part of a three-yearplan which started in 1993, and about 30
types of crude oil were selected from themainstream crude oil imported in Japan. In
the first year, four types of crude oil (OmanCrude, Arabian Light Crude, Murban Crude,Umm Shaif Crude) were used.
Table 1 shows the properties of these
crude oils.
[Conditions of experiment]
The experiment was carried out bothduring the summer and the winter, where theeffects of the different sea water temperatures
and waves were studied. Therefore, weexperimented using four
different factors and their effects on a specific
type of crude oil.
Figures 2 and 3 show weak wave andstrong wave, that is two type of waves
were used in this experiment. The weak
wave is sine wave with smooth surface.
The other strong wave is breaking wave
with rough surface.

Table 1 properties of crude oils
crude Arabian Lt
propertyg/cm3Dens.

Pour Pt

M urbanUmm Shaifcrude

crude

crude

0.86090.84990.82710.8388

APIVis.@15℃

Oman

crude

32.8

34.9

39.5

37.1

cP

9.11

26.7

6.14

6.40

℃

< -30.0< -20.0-24.0< -30.0

T.S

wt%

2.0

0.98

0.78

1.30

Asphalten

wt%

1.7

0.9

0.3

0.1

Resin

wt%

2.5

3.8

2.4

2.5

Table 2. Conditions of experiment
C ase 1 C ase 2 C ase 3 C ase 4
C o n d itio n s(s u m m e r(s) u m m e r ()w in t e r )(w in t e r )W aves
W a v e c o n d itio n
W a v e h e ig h t (c m )F r e q u e n c y (s )W eak

S tro n g W e a k

S tro n g

5‑910‑15

5‑910‑15

10 .5

10 .5
6 .4

W in d v e lo c ity (m / s )

2 .6

6 .4

2 .6

A m o u n t o f s e a w a t e r (t)444

4

D e p th o f s e a w a t e r ( c m )60606060

S e a w a t e r t e m p e r a t u r e (℃ ta r g e2 t5)251010A m o u n t o f c r u d e o il c h a r g e d (L1)0

10

1010

S lic k t h ic k n e s s (m m )

1 .4

1 .4

1 .4

Figure.2

WEAK WAVE

Figure.3

STRONG WAVE

1 .4

[Experiment method]
In the experiment, the water channel was set up to maintain the condition of waves shown in Table
2. When the condition of the wave was consistent, the crude oil was poured gently on the surface of thesea water. The crude oil on the surface of sea water was collected on an increasing time interval up to
96 hours, and its properties were analyzed.
[Experimental results]
1)

Experiment in summer
The experimental results are shown in Figure 4-7.
①

weak wave

Oman crude oil and Arabian Light crude oil formed stable emulsions, while the Murban crude oiland Umm Shaif crude oil, the formed emulsions were found to be unstable.

Particularly for the Murban

crude oil where it gradually dispersed in the surrounding sea water.
②strong wave

Arabian Light crude oil formed a stable emulsion.

Oman crude oil once formed emulsion, but

the emulsion showed indication of degradation after it had formed.

For Murban crude oil and Umm

Shaif crude oil, almost all of it dispersed into the sea water after several hours from the time of thespillage.
2)

Experiment in winterThe experimental results are shown in Figure 8-11.
①

weak wave

Oman crude oil and Arabian Light crude oil formed emulsions. Murban crude oil formed afragile and coarse emulsion with bubbles.

For the Umm Shaif crude oil, it indicated a similar behavior

to that of Murban crude oil.
②strong wave

Oman crude oil and Arabian Light crude oil formed stable emulsion. Murban crude oil and
Umm Shaif crude oil formed fragil and coarse emulsion with bubbles, while a part of the crude oil
dispersed in sea water.

Figure 4Figure 5

[Results of investigation on emulsion using electron microscope]
When crude oil spills in the sea, it is exposed to the meteorological conditions including theatmospheric temperature in the sea area, sea water temperature, and waves, so that light density
components evaporate in a short time.

During the gradual evaporation of medium density components,

the crude oil takes up the sea water. In this case, the crude oil with a large percentage of heavy density
components makes a stable emulsion. In the course of emulsification, the surface of the emulsion
particles was observed using an electron microscope in order to investigate the forming state ofemulsified oil.

Kuwait Crude oil was selected, because it emulsifies easily.

The emulsified oil wasrefrigerated rapidly and was observed with an electron microscope.
Figure 12 shows the initial stage of the emulsification, and Figure 13 shows its enlargement.
These Figures reveal that fine particles of sea water are dispersed in the crude oil, and recessions arefound on the periphery of the sea water particles. These recessions are formed by the sublimation of thelight density components of crude oil during an electron microscope observation.
found in the initial stage of the emulsification.

This phenomenon is

It is also found that the inside of the sea water particles

are exposed by the sublimation of water.

Figure. 12

Figure 14 and 15 show the final stage of the emulsification.

Figure. 13

In these Figures, the recessions asobserved in the initial stage of emulsification reduced and the water particles that are surrounded by theheavy density components were observed.

Figure. 14

Figure. 15[Summary of experimental results]①

The properties of spilt crude oil depend largely on the mechanical properties of the waves andthe sea water temperature.

②

Murban and Umm Shaif crude oils which are particularly rich in light density components,
will disperse into the sea water as fine particles in the summer, and tended to form a fragile andcoarse emulsion with bubbles in the winter.

③

Arabian light and Oman crude oils indicate a tendency of emulsification in each seasons.
But, Arabian light crude oil indicates a large tendency of emulsification in the summer ascompared with that in the winter.

While the Oman crude oil tended to disperse into sea waterwith increase in wave height in the summer.
④

The heavy density components of the crude oil surrounding the sea water particles form astrong protective membrane to cause the emulsification. At this moment, I anticipate resin andasphalten could be key components to cause the emulsification. Resin and asphalten might
function each other.

[CONCLUSION]
On the experimental results, in terms of emulsification tendencies of 4 types of crude oil werecompared.

The Arabian Light crude oil indicated the highest tendency, while the Umm Shaif crude oil

indicated the lowest tendency to emulsify.
[Next plan]
It is evident from the experiment that crude oil spilth at sea is exposed to the meteorologicalconditions of the sea area to be mixed with sea water in various states.

The fact indicates that therecovery of spilt oil should be implemented with the use of best-suited materials, equipment, andprocesses.
In this sense, the accumulation and utilization of data on weathering experiment of crude oil areimportant.

Plenty of experimental data on various types of crude oil will be collected to contribute toall concerned.