How much oil is still left in the ground?

Kishore Mohanty Professor of Chemical & Biomolecular Engineering, Director of the UH Institute for Improved Oil Recovery

Researchers at Cullen College are conducting experiments designed to determine the ability of certain surfactants to draw oil from specific types of rocks.

The idea of buried treasure captures the imagination—riches that have been lost and all-but forgotten, just sitting there for the taking by those clever and industrious enough to find it.

Billions of dollars of buried treasure is really out there. Instead of gold, it is in the form of oil. And instead of being forgotten, everyone knows exactly where it is. According to Kishore Mohanty, professor of chemical and biomolecular engineering and director of the UH Institute for Improved Oil Recovery, most reservoirs that have been pumped and abandoned by petroleum companies still have 60% to 70% of their oil remaining in them.

So why isn’t this treasure being dug up, so to speak? Simply put, getting it out of the ground has proven too difficult. The properties of reservoirs and of the oil itself make retrieving this oil difficult, time consuming and expensive.

Finding ways to overcome these obstacles is the job of the Institute for Improved Oil Recovery, which is currently focusing on two prominent methods of extracting this oil.

One is carbon dioxide flooding, which entails pumping large quantities of carbon dioxide or similar gasses into the ground. The high-pressure gas mixes with the oil and together they flow out of the reservoir. If the gas pressure is not high enough for the two to mix, the gas simply reduces the oil’s viscosity, or thickness, thereby allowing it to flow more easily and be pumped from the ground.

One of the advantages of carbon flooding is its cost. According to Mohanty, this process makes sense financially if oil costs more than about $20 per barrel. There are challenges to the technique, however. These gasses tend to form channels in the oil and escape the reservoir instead of pushing out large amounts of oil. This and other problems are being investigated by the institute.

Surfactants, a class of chemicals similar to detergents, offer another technique for improved oil recovery. When pumped into a reservoir, they bond with both oil and water, allowing oil to flow in the reservoir and up to the surface. Also, in fractured reservoirs, where the rock in the reservoir has long cracks, surfactants stick to rocks’ surfaces, detaching the oil that was there previously and allowing it to flow more easily to the well.

One of the advantages of the surfactant method is that it is easy to implement. The method requires only a small amount of chemicals that can be easily transported to any location. There are hurdles to their use, however. In fractured reservoirs, surfactants work slowly, requiring 20 to 30 years to work fully on large reservoirs. In addition, most surfactants will not be wholly effective when a reservoir’s characteristics (such as rock composition) change notably from one area to another.

The Institute for Improved Oil Recovery conducts tests and performs mathematical modeling to determine which surfactants are most effective for specific types of reservoirs.

These and other methods, said Mohanty, deserve attention because they can deliver huge amounts of oil with little guesswork. “These processes are promising, and they need to be developed,” he said. “We know the oil is there, so there are none of the risks you take with exploration. We just have to improve the recovery technologies. It’s all doable.”

Recoverable Resources
• How much oil is still left in the ground?
• How can we lower the cost of retrieving oil?
• How can we improve the process of oil production?
• What role will petroleum play in an alternative energy future?

Cleaner Consumption
• What can be done to reduce oil consumption in automobiles?
• Are plant-based fuels a realistic solution to our energy demands?
• What is currently being done to improve the air quality in Houston?

Going Green
• What might eventually replace oil and gas in the future?
• What about wind?
• Can we really leverage the moon… for energy?