Experiment OilandCoffee What do a cup of cappuccino and drilling for oil have in common? Foam.

Our story begins when Schlumberger engineer Tony Veneruso made himself a cup of cappuccino. As he sat down to take a first sip, he noticed that the foamy milk topping had collapsed. Thats odd, he thought. Tasting the coffee revealed that he had inadvertently dusted the drink with nutmeg rather than cinnamon, as he had intended. Did the collapse of the milk foam have something to do with the substitution of nutmeg for cinnamon?

Tony quickly assembled his research teamhis three grandchildrenand began a series of experiments. He also contacted SEED Educational Programs manager Michael Tempel, who sent an inquiry to the SEED experts, the hundreds of Schlumberger volunteers who answer the questions submitted to the SEED Web sites Ask the Experts section.

Schlumberger scientist Mathew Samuel not only shed light on the question but also launched his own research program along with colleagues Leiming Li and Lijun Lin. In the oilfield there are situations in which foam can be a problem, from bubbly drilling-fluid mixtures to foamy cement. Traditionally these foams are broken up with a variety of chemicals. Mathew, Leiming, and Lijun saw the possibility of alternative, environmentally friendlier defoamers.

Over the following weeks and months our researchers came up with a variety of defoaming experiments you can try for yourself. They also systematically investigated the feasibility of using nutmeg and other substances as defoamers in the oilfield. So far there have been three patent applications filed for environmentally friendly defoamers, with more on the way.

Photo courtesy of Nick Lott

SEED Experiment: Oil and Coffee Page 2 of 2 Background Before describing our experiments, lets be clear as to what we mean by foam. In addition to the milk foam on the cappuccino, you are probably familiar with soapsuds and maybe whipped cream, meringue, or other light foamy deserts and toppings. These substances all consist of many bubbles of some liquid filled with a gas, usually air.

Tools and Materials Cinnamon powder Nutmeg powder Masala powder Mustard powder Milk, preferably low-fat or fat-free Shaving cream Whipped cream Three egg whites, uncooked (see note) Dish-washing liquid Hand-cranked egg beater Straw Four drinking glasses Shallow bowl Three plates Milk shake blender or any regular blender

Note: How to separate eggs The experiment calls for three egg whites, which means you need to separate the white from the yolk for each of the eggs. To do that, you crack the egg over a bowl and let the yolk settle in one half-shell while the white goes into the bowl. Gently pass the yolk back and forth between the two halves of the shell, allowing more and more of the white to run into the bowl. Once the egg is separated, put the yolk in another container for use later in cooking.

SEED Experiment: Oil and Coffee Page 3 of 3 What to Do We tried a number of different substances that foamed and a number of different spices to see what worked and what did not.

Whipped milk For our first experiment we whipped some milk with a hand-cranked egg beater to produce foam. We poured equal amounts of the foamed milk into each of four glasses.

From left: Masala, Plain, Nutmeg, Cinnamon

Each glass was assigned a spice powder, with one glass left plain as the control. Next we gently sprinkled equal amounts of cinnamon, nutmeg, and masala powder into their assigned glasses. We watched carefully and compared the defoaming action.

After about five minutes the powders clearly started defoaming the milk, with the nutmeg having the most effect.

By ten minutes into the experiment, the foam in the glass with nutmeg had just about reached the liquid level of the milk. In the glasses with cinnamon and masala, the foam was somewhat reduced. Considerable foam remained on the untreated glass of milk.

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After 15 minutes it was clear that defoaming had taken place. The milk in the nutmeg glass was flatno bubbleswhile a bit of foam remained in the glasses treated with cinnamon and masala. The untreated glass still had quite a bit of foam.

We decided to test milk in a slightly different way, to see if the defoaming effect was related to our having used drinking glasses. We put the milk into a shallow bowl and whipped it up with a hand-cranked egg beater.

Then we sprinkled nutmeg at one side and cinnamon on the other, leaving an area in the middle unpowdered.

The nutmeg, at the left, collapsed the foam. The cinnamon had little or no effect.

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Shaving cream and whipped cream For our next round of experiments we tried two foams that are sold in pressurized cans: shaving cream and whipped cream. We tested nutmeg and mustard powders as the defoamers.

We put a blob of shaving cream on each of three plates. We left one plate alone, to be the control plate; sprinkled mustard powder on the second plate; and sprinkled nutmeg on the third.

After one hour there was no observable change. All three blobs of shaving cream remained fluffy.

We tried the same test with whipped cream, and the result was essentially the same. After one hour there was a slight subsiding of the whipped cream on all three plates, with some liquid appearing around the edges. There was no difference between the plain whipped cream, the one with nutmeg, or the one with mustard.

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Dish detergent Next we tried dish detergent. We put water and a bit of detergent into each of two clean glasses. To create foam, we put a drinking straw into the liquid and blew air into the mixture to add bubbles.

We sprinkled nutmeg into one glass and left the other alone. After a few minutes there were fewer bubbles on both glasses, but there was no difference between the two.

We then blew through the straw again into each mixture. We thought that maybe the effect of the nutmeg would be greater now that it was thoroughly mixed in with the water and detergent instead of just touching the surface of the top bubbles. Again, the bubbles broke over time, but there was no difference between the two mixtures.

Egg whites Our final experiment was with three uncooked egg whites, which have been separated from the yolks. We whipped the egg whites with an electric malted machine. A stick blender or regular blender would work equally well.

We distributed the whipped egg whites equally into three glasses and sprinkled nutmeg on one, mustard on a second, and left the third alone. We could see that in the glasses with mustard powder and nutmeg powder, bubbles at the surface were broken. There was a craterlike effect, creating a depression on the surface, that did not occur with the plain egg whites. After a few minutes the volume of foam appeared to be a bit less in the glasses with mustard and nutmeg than in the glass with just egg white.

But what if the bubbles were being broken simply because the grains of powder were being dropped on them? The observed result could be because of a physical popping of the bubbles rather than a chemical reaction. To test this

SEED Experiment: Oil and Coffee Page 7 of 7 hypothesis, we used the approach we had taken with the dish detergent. We whipped the egg whites with the powders already in them.

Again it appeared that the foam held up better with nothing added. Mustard broke the foam somewhat, but nutmeg was a slightly better defoamer.

Now that you have seen what we did, try these experiments for yourself. Can you think of other foams you might try? Would homemade whipped cream (milk and sugar, beaten until frothy) behave differently than store-bought? We tried dish detergent, but what about soap? What other powders might work as defoamers? How about powdered detergent or bath powder?

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Results Looking at all these results together, what have we learned?

Our defoamers had an effect on milk and egg whites but not on commercial whipped cream, shaving cream, or dish detergent.

Nutmeg appears to be the most effective defoamer, with mustard also effective. Masala had a slight effect on milk.

The effect of cinnamon on milk foam is unclear. In one experiment it had an effect and in another it did not. In any case the effect of cinnamon was weaker than that of nutmeg, as indicated in the initial cappuccino experience.

The results for masala are inconclusive because this spice is actually a mixture of many substances and there is no standard masala. We would have to isolate the particular ingredients to test separately.

Why didnt our defoamers have an effect on shaving cream, whipped cream, and dish detergent? We believe this is due to chemicals that are added to these products precisely in order to keep them foamy. You do not want the shaving cream to go flat before you finish shaving. You want that mound of whipped cream to stay fluffy on your desert. These commercial products are designed to resist defoaming.

How Defoamers Work To understand how foam gets broken up, we need to understand how a foam forms, whether in the kitchen, the lab, or in a big field operation. When air or other gases bubble through a liquid that contains dissolved surfactant molecules (chemicals that can greatly reduce the surface tension of water when used in very low concentrations), a foam may occur.

The surfactant molecules form micelles, groupings of surfactant molecules, each of which has a hydrophilic (water-loving) head, and a hydrophobic (water-fearing) tail. In water, the hydrophobic tails aggregate to each other, surrounded by the hydrophilic heads, which form a skin in contact with the water. In foamed milk or detergent suds, there are micelles of different lengths. Some are longer and wormlike, while others are smaller and spherical.

SEED Experiment: Oil and Coffee Page 9 of 9 Worm-like micelle Spherical micelles

The molecules that make up a micelle have a hydrophilic head, shown in blue, which is attracted to water, and a hydrophobic tail, shown in gray, which avoids water. If a substance has more wormlike micelles than spherical ones, its viscosity is higher. Of several factors, viscosity is the most important one in determining how stable the foam ishow long it lasts. Therefore, surfactants with more wormlike micelles have longer-lasting bubbles.

Eventually all foams will break up naturally owing to the drainage of the liquid associated with the gravity. Surface tension and viscosity work to keep the skin of the bubble together. At the same time gravity is trying to pull the liquid down from the top. When gravity wins, the top of the bubble is pulled open and it pops. This is drainage.

Defoamers act by breaking up the wormlike micelles into smaller spherical micelles. This reduces viscosity, causing the bubbles to pop. But what is the mechanism for breaking up the long micelles?

The key ingredient is oil. You can see the effect of oil on foam when you wash your hands with soap. If your hands are already clean, washing with soap and water will produce suds. Now try the same thing but first rubbing a bit of oil on your hands. There will be few, if any, suds. Oil breaks up the long micelles into smaller micelles, because some of the hydrophobic tails bond to the oil molecules rather than to each other. Thus the foam breaks down more easily.

A variety of chemicals including kerosene, alcohols, and oils may be used to get rid of foams that are no longer needed. These types of chemicals are also used to suppress the formation of foams in the first place. Unfortunately, some of these chemicals are not environmentally friendly or are flammable. Using these chemicals presents further cleanup and disposal problems.

Using substances such as nutmeg and mustard as defoamers may be an environmentally friendlier solution. Nutmeg and mustard powder come from seeds with a high oil content. This oil reacts chemically with the micelles and breaks them up. There are probably many other food substances besides the ones we tested that have high oil contents and may have the same defoaming properties.

SEED Experiment: Oil and Coffee Page 10 of 10 Defoamer Needs in the Oil and Gas Industry We mentioned at the beginning of this experiment that a group of Schlumberger scientists became very interested in Tonys cup of cappuccino. Their research has so far generated a number of patent applications for environmentally friendly defoamers. What does defoaming have to do with the petroleum industry?

There are several steps in the process of drilling for and recovering oil that require the use of fluids. Under some conditions these fluids get foamy, and this can cause problems. The foam needs to be broken up.

Drilling fluid

When an oil well is being drilled, the drill bit is at the end of a long hollow pipe. A liquid called drilling fluid, or drilling mud, is pumped down this pipe, emerges at the bottom, and flows back to the surface in the space between the pipe and the sides of the hole being drilled. Drilling fluid contains a variety of chemicals and solids, depending on the rocks being drilled through and the environmental conditions in the area.

The drilling fluid serves several purposes. One is to remove cuttingsthe pieces of rock that are cut from the rock formation being drilledfrom the borehole. The

cuttings are carried to the surface by the flow of the drilling fluid. This prevents the cuttings from accumulating at the bottom, where they would jam the drill bit and prevent further drilling.

Drilling fluid also maintains a proper pressure balance inside the borehole. There must be enough pressure to prevent oil or water from flowing into the boreholebut not so much that it causes the drilling fluid itself to be lost into the rock formation.

At times drilling fluid foams as it reaches the surface. The reason: gas bubbles that form as the pressure decreases near the surface. This is similar to what happens when you open a can or bottle of a carbonated drinkthe gas bubbles come out of solution as the pressure drops when the container is opened. Foaming drilling fluid can be difficult to pump and messy to clean up. The solution is to use defoamers.

Cementing Once an oil well has been drilled, a steel pipe is inserted into the borehole and cemented in place. This stabilizes the well and prevents fluids from leaking in or out. The cement is pumped into the space between the pipe, called a casing, and the walls of the borehole. This cement may foam as it

SEED Experiment: Oil and Coffee Page 11 of 11 nears the surface and will need to be cleaned up. Defoamers help reduce the volume of foam and make cleanup easier.

Stimulation After a well has been producing oil for some time, the flow of oil may be reduced. This happens because the pores in the formation get clogged with organic material such as tars and paraffin or inorganic salt deposits such as calcium carbonate, barium sulfate, barium carbonate, and sodium chloride (salt). When this happens, the oil and gas production can be increased by a method called stimulation. Stimulation, which can prolong the productive life of the well, works by forcing liquids into the rock formation. This opens up cracks or wormholes, allowing more oil to flow. Stimulation fluids are foamed to maximize efficiency, but the foam needs to be broken down when the fluid returns to the surface.

New Defoamers The lessons we learned from our experiments reducing foams with nutmeg have now been extended to so-called breaking gels used in hydraulic fracturing, a stimulation method that increases well production. These gels are surfactants that form micelles. Nutmeg, coconut, and other oil-bearing nuts can alter the viscosity of these gels to the point where their viscosity is like that of water. This will help quicken the cleanup of wells, which can have a big impact on business.

Our simple experiments show how understanding the science of foam in a cup of cappuccino is important to develop better oil drilling, cementing, and stimulation technology. They also demonstrate how important it is to follow your curiosity about the amazing things in the world around you.