Radar Locates Offshore Oil Slicks
Shell and RSI collaborate on acquiring the first RADARSAT images of the Gulf of Mexico.
By Sylvie Scantland and Ed Biegert

Satellite information is helping petroleum geologists determine the potential of new oil reserves worldwide. In particular, newly available radar technology is providing increased dependability, improved cost effectiveness and more rapid access to information that can be vital in detecting and monitoring naturally occurring oil slicks. Several projects have been conducted to evaluate how best to use satellite information technology, specifically radar satellite data, in offshore exploration. One successful program is the Gulf Offshore Satellite Applications Project (GOSAP).
      Formed in 1990, GOSAP is sponsored by the Geosat Committee Inc., a not-for-profit remote sensing industry group. As a cooperative project, GOSAP counts among its participants international oil and gas companies, research organizations, universities, sophisticated users of remote sensing data, data suppliers, and value-added companies who are working together to define problems, implement solutions, and develop commercial products. RADARSAT International (RSI), a Richmond, British Columbia, Canada based company, has worked with the GOSAP team during the past four years to facilitate the delivery of radar data from the ERS -1 satellite, and in the future, from the RADARSAT satellite. RSI distributes ERS data in North America and is the exclusive worldwide distributor of RADARSAT data.
      In 1993 and 1994, GOSAP verified the utility of ERS-1 radar satellite data for oil slick detection in a number of sea-truth exercises conducted in the Gulf of Mexico. "As a result of our studies using ERS data, we determined that radar technology is a cost-effective method for oil seep detection, with less sensitivity to weather conditions than traditional optical satellite data," said GOSAP Director Dr. Ed. K. Biegert. Dr. Biegert works at Shell's International Center for Remote Sensing and Potential Field Studies.
      "ERS-1 was used with tremendous success to detect oil slicks but was severely limited due to lack of a data recorder. Parts of the ocean of interest to our clients just were not accessible," said John Amos of Earth Satellite Corp., a key GOSAP participant.
      The versatile RADARSAT satellite, operated and managed by the Canadian Space Agency (CSA), is equipped with a Synthetic Aperture Radar (SAR) which obtains strips or swaths of HH polarized imagery from 50 to 500 kilometers in width with selectable resolutions from 10 to 100 meters. With its worldwide geographic coverage -- unavailable from any other single satellite source -- RADARSAT offers an advantage over the more traditional optical satellites and other radar satellites.

Detecting Oil Slicks Using RADARSAT
With the recent availability of RADARSAT data, GOSAP is now performing a similar verification using RADARSAT data as part of the RADARSAT Application Development and Research Opportunity (ADRO) Program. ADRO is sponsored by the CSA, the National Aeronautics and Space Administration (NASA) and RSI.
      Specifically, the GOSAP team is using RADARSAT data to detect and identify natural oil slicks in the Gulf of Mexico, and other international sites to verify the presence of slicks detected in all of the beam modes available from RADARSAT.
      Extensive calibration data for a GOSAP test site in the deep water of the Gulf of Mexico will be used to evaluate the effectiveness of RADARSAT data for oil slick detection. In addition to the RADARSAT data, a wide range of other information will be used, including imagery from other satellites, airborne sensors, and the Space Shuttle Atlantis, observations and geochemical measurements made at the ocean surface, and samples taken from active seeps at the sea floor.
      "Combining RADARSAT imagery with this information will aid us in distinguishing natural oil seeps from man-made and biological slicks," noted Dr. Biegert.
      "The RADARSAT scenes that we have used have provided very high quality imaging of sea-surface features, including some of which we have not seen before. It thus appears that a wide variety of RADARSAT beam modes will be useful for mapping oil slicks," added Dr. John Berry of Shell E & P Technology Company's International Center for Remote Sensing and Potential Field Studies.
      Also, the GOSAP team plans to conduct a "sea truthing" verification program that will include ocean surface sampling from ships and platforms, sea bottom submarine observations, and aircraft overflights. Sea truth results will help evaluate the ability of RADARSAT to detect oil slicks under a variety of environmental conditions and acquisition modes.
      "Radar technology has already been proven reliable in detecting seeps," said Sylvie Scantland, RSI Sales Director for the Eastern United States. "RADARSAT's edge is that it user-oriented. As the most flexible radar satellite available, the RADARSAT system offers more geographic coverage per scene, coverage of virtually any location worldwide, and rapid data delivery. The resulting cost-effectiveness can be significant.
      "For example, one of RADARSAT's ScanSAR Narrow beam mode products, which covers an area of 300 x 300 kilometers with 50 meter resolution, would require nine ERS scenes to cover the same area. Another RADARSAT product, from RADARSAT's Wide beam mode, covers 165 x 165 kilometers and has 30 meter resolution, would require four ERS scenes to provide the same coverage. Thus, geologists can save time in processing, mosaicking, enhancement, as well as save money in purchasing the data itself."
      As the world's first operationally oriented commercial Earth observation satellite to employ Synthetic Aperture Radar (SAR), RADARSAT through RADARSAT International offers users new opportunities to view and monitor offshore oil slicks. RSI is committed to working with the remote sensing user community to evaluate and implement application solutions to benefit commercial operations.

About the Authors:
Sylvie Scantland is sales director, Eastern United States at RADARSAT International. She can be reached at telephone: 613-238-6413, fax: 613-238-5425, e-mail: [email protected]. Dr. E.K. Biegert is the director of GOSAP and can be reached at the International Center for Remote Sensing and Potential Field Studies, Shell E&P Technology Co. He can be reached at telephone: 713-245-7120, fax: 713-245-7850, email: [email protected].

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