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Different liquids have different properties. One of these
properties is viscosity, the liquid's resistance
to flowing. Water, milk, and fruit juice are comparatively
thin and flow more easily than thicker, more viscous liquids
such as honey, corn syrup, shampoo, or liquid soap.
Viscosity is an important property of drilling
fluids. A more viscous fluid is better able to suspend
rock cuttings and transport them to the surface. However,
more pressure is needed to pump very viscous fluids, resulting
in additional wear and tear on the drilling equipment. Viscous
fluids are also more difficult to separate from the cuttings.
One way to test the viscosity of a liquid is to see how much
time an object takes to sink in it. You can also compare viscosities
by comparing the sinking times for different liquids.
- Water
- Baby oil (or some other easily obtainable light oil)
- Clear or light colored shampoo
- Clear plastic bottle about 444 mL (15 oz) capacity or
slightly larger, with tightly fitting cap
- 35 mm film canister or similar small object
- Stopwatch that measures to 0.1 or 0.01 seconds
- Glass marble small enough to fit through the mouth of
the bottle
- Permanent marking pen
- Safety goggles
- Chart like the one below to record your results
1. On the side of the bottle about 3 cm (1 in) from
each end, draw two lines with a permanent marking pen.
2. Insert a marble in the bottle, fill the bottle to
the top with water, and close the cap tightly. |
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3. Invert the bottle and observe the marble dropping
through the water. (It drops very quickly.)
4. With the stopwatch, try to measure the time it takes
for the marble to drop from one line on the bottle to
the other when you invert it. (This is nearly impossible
to do, because the marble drops so quickly. The water
is not very viscous.)
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5. Let’s try another technique. Place the bottle
on its side with the cap resting on a film canister
or other small object. This makes a gentle ramp for
the marble to roll down. If the ramp is not very steep,
the marble will roll through the water slowly enough
for you to time it.
6. Raise the end of the bottle so that the marble rolls
to the cap end.
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7. Place the end of the bottle down quickly but gently.
Use the stopwatch to measure the time it takes for the
marble to roll from one line on the bottle to the other.
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8. Record the time in the Water column
of the data table opposite Trial 1.
9. Repeat four more times and calculate the average
time for the water.
10. Replace the water in the bottle with baby oil.
(Or, pour baby oil into an identical bottle with marks
in the same places.) Insert a marble and close the cap
tightly. Repeat steps #5 through #9 to obtain the results
for baby oil.
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Take a look at our
results.
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11. Optional: For an encounter with a much more viscous
liquid, try this experiment with a marble in a bottle
of shampoo. Invert the bottle and measure the time it
takes for the marble to drop. Depending on the type
of shampoo you have, this could take 30 seconds or even
more! The shampoo is much more viscous than water. (If
you make a gentle ramp with the bottle and let the marble
roll down through the shampoo, you might as well get
a favorite book to read while you wait! This seems to
take forever!)
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