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Scientist proposes new heavy oil process Wants to establish a facility in Fairbanks to test the use of high pressure and temperature water to crack oil at the wellhead Alan Bailey Petroleum News
The many billions of barrels of heavy oil lying at shallow depths under Alaska’s central North Slope have spurred much interest in finding viable ways of turning this huge resource into a marketable commodity. Heavy oil, with a consistency of honey, is difficult to extract from an oil reservoir and equally difficult to ship unaided down an oil pipeline. Heavy oil also suffers from the disadvantage of being inherently less valuable that conventional light oil.
BP has had some success in initial tests of heavy oil production from the Ugnu formation above the Milne Point field on the North Slope, using a cold extraction technique involving a downhole pump in conjunction with a horizontal well. But the company has yet to verify the long term characteristic of its test production techniques, or to establish commercial viability of heavy oil development.
New technique On Jan. 18 Stephen Yarbro, a scientist at the Los Alamos National Laboratory and owner of SNT Ventures LLC, told the Alaska Senate Resources Committee about a new technique that he says may enable the cracking of heavy oil into light oil at the wellhead, creating oil that could readily flow through a regular pipeline and that would have a higher value than the heavy oil from which it is generated.
Yarbro told the committee that his technique might supplement the type of approach that BP is testing. He said that laboratory testing of the heavy oil cracking technique had proved successful and that he wants to work with the University of Alaska Fairbanks to set up a facility at the Fairbanks Pipeline Training Center, to test the technique on a more industrial scale. He would like the Alaska Legislature to consider awarding a grant for the test project.
“We believe that the technology, if properly developed and successful, could provide more oil for the trans-Alaska pipeline and this has a variety of positive effects,” Yarbro told the committee.
Supercritical water Essentially, the technique, called supercritical water extraction and refining, or SCWER, involves mixing oil with water at high pressure and temperature, Yarbro explained. Under these conditions, with temperatures and pressures above what is known as the critical point, water becomes a supercritical fluid, rather than being either a liquid or a gas. And water in this supercritical form can dissolve oil, despite the fact that at more normal temperatures and pressures oil and water are insoluble.
“We use the unique properties of water at very high temperatures and pressures, beyond its critical point, to essentially dissolve the heavy oil,” Yarbro said. “Oil dissolves completely in water past its critical point.”
The high pressure and temperature of the supercritical fluid causes the oil molecules to break apart, eventually resulting in the complete degradation of the oil to carbon dioxide if the process is allowed to run to completion. However, laboratory tests have shown that by carefully controlling the process it is possible to stop the breakdown of the oil at a point where the components of light oil have formed. In effect, the very long chains of hydrocarbon molecules that typify heavy oil break up into the short chains typical of light oils, with hydrogen from the water combining with the severed ends of the chains.
“We’ve carefully looked at the conditions to get to the point where we just get enough thermal degradation to get the (oil) products of value,” Yarbro said.
Oil from asphalt Yarbro showed the committee photographs from a lab experiment in which the SCWER technique had converted roofing asphalt into light oil. At the end of the experiment, the light oil floated to the top of water in a flask, while sand that had been embedded in the asphalt had sunk to the bottom of the flask.
The laboratory tests also demonstrated that the oil cracking process actually increased the volume of processed oil by about 9 percent, a factor that could further increase the value of heavy oil production, he said.
Yarbro said that several years ago the Los Alamos Laboratory had successfully developed a similar technique for removing organic material from radioactive waste — organic material breaks down in a manner analogous to oil when dissolved in supercritical water. And the military has licensed a variant of the process for the destruction of chemical weapons, he said.
Electric heaters The system that Yarbro envisages for heavy oil treatment would involve the use of electrical heaters to heat pressurized water and oil beyond the critical point. Then, because the subsequent breakdown of long hydrocarbon molecules into shorter molecules would itself generate heat, the heat required for the oil processing system would be partially self sustaining. The operating temperature range would be somewhere around 350 F to 450 F, he said.
And once the cracking of the heavy oil had been completed, subsequent cooling of the resulting fluid would cause the water and the generated light oil to liquefy and separate, with the oil floating to the water surface for recovery. Most of the water could be recycled through the process, although some water would have to be drawn off for the disposal of impurities such as sulfur compounds, generated as part of the process. An input stream of water would keep the water level topped up.
The energy requirements per barrel of oil processed should be similar to the mid-point or lower range of the energy requirements of a conventional refinery, he said. And steam from the plant might also find a use in the extraction of heavy oil from the underground oil reservoir rocks, should heat be needed to improve extraction rates.
Standard modules Yarbro envisages a production system involving a series of standardized 25-barrels-per-day SCWER units, a unit size that he thinks represents the smallest practical industrial scale. It should be possible to manufacture a large number of these units from standard petrochemical equipment and then position however many units are needed at a heavy oil wellhead site, he said.
Financial modeling of the process indicates a cost of $10 to $14 per barrel of oil processed, depending on the supporting infrastructure available at the processing location, Yarbro said. Process viability would presumably depend on increasing the wellhead value of the oil by more than the processing cost.
The test facility that Yarbro would like to establish at the Fairbanks Pipeline Training Center would operate at five barrels per day, a capacity that Yarbro says would be sufficient to test the process as an industrial application and to answer some questions that were not resolved from small-scale lab testing. Success with the proposed testing in Fairbanks could pave the way for scaling up the technology for commercial oil production, he said.
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