orld Energy Systems Incorporated (WES), an independent research company in Fort Worth, Texas, is developing technology that economically recovers dense, viscous deposits of heavy hydrocarbons (often called very heavy oil, tar sands, or natural bitumen) that are difficult or impossible to recover with existing technology.

Technology Overview

In the WES process, superheated steam and hydrogen are injected into a formation containing heavy hydrocarbons, which initiates conversion of the heavy hydrocarbons into lighter hydrocarbons. In effect, the heavy hydrocarbons undergo partial underground refining that converts them into a synthetic crude oil (or syncrude). The heavier portion of the syncrude is treated to provide the fuel and hydrogen required by the process, and the lighter portion is marketed as a conventional crude oil. Computer simulation shows the process works successfully, but it has not yet been field tested.

Research to Date

Development of the technology began in the laboratory, with testing conducted by both the U.S. Department of Energy at a DOE facility ⁽¹⁾ and by WES at the company’s research center ⁽²⁾.

Numerous samples of heavy hydrocarbons from deposits throughout North America were heated in the presence of varying concentrations of hydrogen.

For all heavy hydrocarbons tested, the rate of conversion to lighter oil, as measured by API gravity, increased with temperature. Results for one heavy oil are shown in Figure 1.

With increasing hydrogen concentrations, the degradation to coke decreased and, correspondingly, the total amount of light oil recovered increased. Figure 2 shows results for multiple tests on one heavy oil for which all conditions were identical except for hydrogen concentration.

Utilizing these laboratory results, WES designed an integrated process that operates above and below ground:

• Below ground, superheated steam and hot hydrogen are injected into a heavy hydrocarbon formation, which simultaneously produces the hydrocarbon and converts it in situ (i.e., within the formation) into syncrude.
• Above ground, the heavier fraction of the syncrude is separated and treated on-site to produce the fuel and hydrogen required by the process, while the lighter fraction is sent to a conventional refinery to be made into petroleum products.

Figure 3 shows a schematic of WES’s integrated system.

After the integrated system was designed, WES conducted a series of computer simulations to study the application of the technology to an actual heavy hydrocarbon deposit ⁽³⁾. With computer simulation, a large bitumen deposit in Maverick County, Texas, known as the San Miguel tar sand, was subjected to in situ conversion.

In the 1980s, Conoco conducted several field tests in which the San Miguel tar was produced by injecting steam at temperatures high enough to melt the tar but not high enough to convert the tar into syncrude ⁽⁴⁾. WES’s computer studies permit a comparison of the effectiveness of the in situ conversion process to the steam-injection process that produces only unconverted tar.

Figure 4 summarizes results from one computer run that mimicked the Conoco tests and two computer runs in which the in situ conversion process was applied.

As the figure shows, steam injection produced half of the hydrocarbon in place, while the conversion process produced 90% of the hydrocarbon in place. In addition, in situ conversion transformed a significant portion of the recovered tar into syncrude, but there was negligible conversion of tar into syncrude using steam injection.

Future Research

Following are the tasks required to complete a field test of WES’s in situ conversion process and bring the technology to commercialization:

1. Conduct additional computer runs focused on optimizing the process.
2. Select a heavy hydrocarbon deposit for field testing and conduct laboratory experiments to measure the rate the selected hydrocarbon converts to syncrude over a range of process conditions.
3. Utilizing the laboratory data from Task 2, conduct computer simulations of in situ conversion of the hydrocarbon to design a field test.
4. Using the field test design from Task 3, construct and test a prototype downhole combustion unit.
5. Conduct a field test in the selected hydrocarbon deposit using the combustion unit constructed in Task 4 in accordance with the design developed in Task 3.

The successful completion of these tasks prepares the way for producing extensive deposits of heavy oil and natural bitumen in the U.S. and Canada. If half of the heavy hydrocarbon resources in the U.S. and Canada can be brought to market, they would alone satisfy the current demand for crude oil in both countries for more than 150 years.

References

4. Britton, M.W. et al., “The Street Ranch Pilot Test of Fracture-Assisted Steamflood Technology,” Journal of Petroleum Technology, March 1983.

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