Characterization of natural hydrocarbon seepage in the South Caspian Sea off Iran using satellite SAR and geological data

Abstract

Two groups of oil slicks have been repeatedly detected in the Southern Caspian Sea, off Cape Sefidrud and close to the Iranian coast of the sea on the synthetic aperture radar (SAR) images acquired by the Sentinel-1A and Sentinel-1B satellites in April–June 2018. Analysis of the SAR images together with bathymetry, geological and geophysical data in geographic information system showed that these manifestations (oil slicks) visible on the sea surface have natural origin, related to the bottom seepage phenomenon and are associated with existing hydrocarbon system. Oil slicks are concentrated over the continental slope and related to local geological formations of the sedimentary cover having oil deposits related to paleo-delta of Sefidrud River. Our evidence shows that two seeps in this area are active and repeating. It is concluded that the SAR is an excellent tool for monitoring of seepage phenomenon. Moreover, results indicate that the use of remote methods to identify offshore natural oil seeps related to existing active petroleum system can be considered as a well-accepted approach to support oil and gas exploration in frontier areas such as the South Caspian Basin.

Keywords:

• Cape Sefidrud
• Caspian Sea
• hydrocarbon seeps
• oil spill
• synthetic aperture radar (SAR)

Acknowledgments

The authors thank Khazar Exploration and Production Company for valuable data on oil fields in the South Caspian Sea. The Sentinel-1A, Sentinel-1B, Sentinel-2, and Landsat-8 images were accessible from open resources; all rights to them belong to European Space Agency and U.S. Geological Survey.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The Russian Foundation for Basic Research (project 17-55-560008) and Iran National Science Foundation (project 96003650) provided financial support for this research in the frameworks of the joint project “Comparative research of fluid dynamics of the Middle and South Caspian sedimentary basins.”