By Thomas Guengerich
SOCORRO, N.M., Aug. 22, 2008 – New Mexico Tech researchers have secured more than $1.5 million in state and federal funds to research the use of polymers for enhanced oil recovery.
Randy Seright, senior engineer and associate director of the Petroleum Research and Recovery Center at Tech, will spearhead the effort to examine new technology and new processes for recovering hard-to-reach oil, specifically on the North Slope of Alaska.
The U.S. Department of Energy awarded $1 million to the center, while the state of New Mexico added $500,000. The project aims to find efficient, cost-effective methods of recovering heavy oil, which is more than 1,000 times more viscous than normal light crude oils.
The three-year project will employ a handful of researchers, including Seright, a senior technician, three graduate students, two undergraduate students and a rotating cast of visiting scientists. The majority of the project will involved laboratory experiments and computer modeling. However, Seright has already started to build a consortium of industry partners who could potentially test the new discoveries in the field.
Over the life of the project, the cast and crew aim to provide new techniques for heavy oil production around the world. In most oil fields, existing technologies can recover only about 30 percent of existing oil.
On average, the first 15 percent of oil in a reservoir is easily extracted by drilling a well and allowing the natural pressure to force oil up through the wellhead. This method is called primary recovery.
“When the pressure declines, the oil stops flowing,” Seright said. “We can get, on average, another 15 percent of a reservoir through secondary recovery. We drill a pattern of secondary wells and inject water to push oil toward the production wells.”
The process of water flooding works well with light crude –¬ oil that is thin and less viscous – but is not as effective with heavy, viscous oil, he said. Oil with high viscosity is a thick, tar-like substance.
“Mother Nature gives us a broad range of types of oil,” Seright said. “Some oil is light, like the oil found in West Texas. Other oil is more viscous. Think of asphalt or tar, which is a byproduct of crude oil.”
Enhanced oil recovery – or tertiary recover – uses artificially-induced pressure by means other than water to force oil into the wellhead, Seright said.
Thick – or viscous – oil is more difficult to get out of the ground and more difficult to refine. Seright’s research project will investigate methods of injecting water-soluble chemicals – or polymers – mixed with water to enhance the recovery of viscous oil from reservoirs where oil cannot be produced using existing technology.
“Water has a low viscosity,” he said. “If I inject water into high-viscosity oil, the water will just channel through the oil. If I want a more efficient displacement of heavy oil, I need to increase the viscosity of what I’m injecting.”
To accomplish that goal, Tech researchers are exploring chemical additives – specifically, polymers – that can make a water-based solution more viscous. By injecting polymers into oil reservoirs, the more-viscous fluid will push more oil toward production wells.
A polymer is a very long molecule. Water has a molecular weight of 18. Some polymers have a molecular weight of up to 30,000,000. The higher molecular weight loosely translates to higher viscosity – and thickness of a fluid.
Water-soluble polymers are often used to make common products – such as shampoo and ice cream – more viscous, or less “runny.”
Seright’s research will examine different formulae of polymers and different methods of delivering the polymers to oil reservoirs to maximize output.
Currently, two commercially available water-soluble polymers seem to fit the bill: polyacrylamide and xanthan, neither of which are toxic. Polyacrylamide is used in paper-making and wastewater treatment. Xanthan is most commonly used as a food additive.
During the project, Seright and his team of researchers will consider new polymers as well.
“Cost-effectiveness is a very important issue,” Seright said. “Other polymers are available, but xanthan and polyacrylamide have more advantages.”
The team will also examine the use of horizontal wells, which can tap the side or the bottom of an oil reservoir – a relatively new recovery tool that has dramatically increased the efficacy of oil and gas recovery.
“Ten to 20 years ago, most wells were vertical,” Seright said. “Over the past few years, horizontal wells have become more common. We can use a polymer more efficiently by horizontally tapping into a reservoir.”
– NMT –