DE-FG02-05ER84198

Goal
The project goal is to develop downhole heater cables to provide high power, at preferably high voltages, to heat oil shale and rock to about 900° C and to demonstrate the feasibility of using this heater technology for the in-situ recovery of oil from shale.

Performer
Composite Technology Development, Inc. (CTD), Lafayette, CO

Schematic of downhole heater design.

Background
While the quantity of oil shale is significant, cost-effective methods of recovering and refining the material still must be developed. One method of extracting oil shale involves the use of underground heaters to separate kerogen (the organic material from which oil is derived) from the shale in situ. In this process, heater cables 2,000-5,000 feet long are deployed in oil shale deposits and heated to at least 500° C. Heating the oil shale in-situ converts the kerogen to a petroleum-like substance. Additionally, the heat reduces the viscosity of the organic material and allows the newly formed oil to be readily pumped to the surface for refining.

At this time, one of the biggest technical challenges associated with in-situ heating is the development of heater cables capable of long term, high temperature operation in downhole environments. These heater cables need to provide high power, at preferably high voltages, to heat the oil shale and rock to about 900° C. The higher the power each heater is able to provide, the fewer the number of heaters that will need to be installed for a given volume of rock. High thermal conductivity of the conductor and the insulation is required to make the heaters as highly efficient as possible. Furthermore, the heater cables need to be able to be installed downhole in a manner similar to which the oil industry uses for installing equipment downhole, such as that used for coiled tubing. Two primary challenges associated with the development of heaters for in-situ oil shale recovery are the electrical insulation material and a cost-effective manufacturing method with which to fabricate these heaters.

Potential Impacts
The benefits of developing in-situ process technologies are as follows:

• The economic viability of oil shale recovery is dramatically improved by eliminating the cost of mining kerogen-containing rock and bringing it to the surface for processing.
• The long-term security of the U.S. oil supply is significantly improved because the Nation ultimately could be self-sufficient in oil following a comprehensive program to fully develop its oil shale resources.
• The environmental impact is minimized because the process takes place several thousand feet below the Earth’s surface. The in-situ process 1) does not generate significant quantities of spent rock that must be disposed of and 2) will enable the rapid re-vegetation of the site.

The timely development of these new materials will position CTD to be a provider of high-temperature heater cables for use in in-situ oil shale recovery processes. This technology will enable the exploitation of the United States’ valuable domestic resources of oil shale, thus reducing its dependency on foreign oil.

Accomplishments
In Phase I, CTD developed and evaluated new high-temperature insulation materials that meet the difficult requirements for in-situ oil shale recovery and developed and tested the performance of these materials in full power, limited-length heater cable development specimens. In Phase II, CTD concentrated on development and scale-up of a manufacturing process that can cost-effectively manufacture these cable heaters in lengths relevant to the oil shale recovery system.

Specific Project highlights include the following:

• Researchers demonstrated the feasibility of downhole heaters for in-situ recovery of oil from shale.
• The heaters utilize a patented high-performance, ceramic-based composite insulation
• After more than 5,000 hours of continuous high-temperature electrical tests, CTD’s insulation provides a lower, more stable leakage current than is attainable with commercial products, such as mineral insulated (MI) cables.
• High-temperature testing was performed, in-kind, by an industry collaborator; testing was not a part of the original Phase I scope, but technology maturity was sufficient to garner industry interest.
• Compared with MI cables, CTD’s heaters show that they:
  • Provide more stable electrical insulation over time at high temperature.
  • Can be manufactured in significantly longer lengths without the use of joints or splices.
  • Can be manufactured for higher current-carrying capacity with a larger conductor.
  • Are far less sensitive to moisture and are more flexible and can be spooled to a smaller diameter for more-efficient transport and ease of insertion into the wellbore. Heaters based on similar technology can be used for enhanced oil recovery and recovery of oil from tar sands.

Current Status
Composite Technology Development, Inc. (CTD) has completed Phase II of a Small Business Innovation Research (SBIR) project. The final report is provided below. They have designed and tested a high-performance, high-temperature downhole heater cable for application in oil shale recovery using in situ methods. The ceramic insulated cable has undergone 5,000 hours of continuous testing at temperatures ranging from 760 to 850oC; well within the range needed for converting the organic matter in oil shale to kerogen. CTD’s effort included the development of the insulated cable fabrication process. The CTD technology overcomes many of the limitations of existing high-temperature heater cables including conductor instability, moisture-induced degradation, and limited operating temperatures insufficient for shale oil recovery. In addition to oil-shale recovery, the technology developed by CTD also has potential applications for enhanced oil recovery (EOR), geothermic fuel cells, and geothermal energy production.

As a result of this SBIR program, CTD has filed two patent applications related to the technology described herein. One of these describes the deployment of heater cables with greenstate insulation, and the subsequent conversion to the ceramic state using the heater to initiate this reaction. The second application describes the field-joining of heater cables based on the technology described herein. The authors, title, and application number of the two patents are:

• M.W. Hooker, M.W. Stewart, P.E. Fabian, and M.L. Tupper, “In-situ Processing of High-Temperature Electrical Insulation”, U.S. Patent Application 20070199709, August 30, 2007.
• M.L. Tupper and C.S. Hazelton, “Field Application of Polymer-Based Electrical Insulation”, U.S. Patent Application 20070181306, August 9, 2007.

Project Start: June 27, 2005
Project End: August 6, 2008

DOE Contribution: $849,837
Performer Contribution: $0

Contact Information
NETL – Robert Vagnetti (robert.vagnetti@netl.doe.gov or 304-285-1334)
Composite Technology – Matthew Hooker (matt@ctd-materials.com or 303-664-0394)

Additional Information
Final Project Report [PDF-853KB]