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Monitoring of the Cantarell Oil Seep in the Campeche Bay, Southern Gulf of Mexico, Using ENVISAT ASAR Data

Enrico Pedroso(1) , Miguel Herrera(2) , Fernando Pellon de Miranda(3) , Karen Bannerman(4) , Ricardo Caceres(4) , Carlos Beisl(1) , and Luiz Landau(1)

(1) COPPE/UFRJ, CT Bloco I-114 Ilha do Fundao, RIO DE JANEIRO, Brazil
(2) PEMEX, Calle 25 No. 48, Cd del Carmen 24130, Mexico
(3) Petrobras, Cid. Universitária Ilha do Fundão - Quadra 7 , Rio de Janeiro 21949-900 , Brazil
(4) MDA, 13800 Commerce Parkway, Richmond, V6V2J3, Canada

Abstract

Natural oil seeps have historically provided invaluable information to oil explorers in offshore frontier areas. Mexican exploration activities began soon after a fishermen, Mr. Cantarell, reported oil seeps in the Campeche Bay. The complex of oil fields later discovered beneath the seeps was subsequently named after him. Important fisheries and delicate ecosystems surround this offshore region, making it highly sensitive to the presence of oil. In this context, an understanding of the temporal dynamics and spatial distribution of natural seepage phenomena is fundamental for the definition of proper environmental management practices.

This paper presents ENVISAT ASAR results as part of a systematic monitoring program carried out by PEMEX Exploración and Producción in the Campeche Bay, southern Gulf of Mexico, which includes the integrated analysis of multi-sensor data for seepage slick detection. The continuous use of ENVISAT ASAR and RADARSAT-1 data increases the possibilities of image acquisition in the vicinities of Cantarell, therefore reducing the gap between data takes in a situation that requires routine monitoring of a large area consistently, reliably and independently.

Although SAR images are very useful for offshore oil detection, several other phenomena at the ocean surface also produce regions of low radar backscatter that, in turn, can lead to misinterpretation. Thus, the success of ENVISAT ASAR in detecting a seepage slick is a function of the environmental and weather conditions prevailing on the image acquisition date. Oceanic and meteorological ancillary data and derived analysis are therefore integrated in this study in order to aid in the interpretation of the ENVISAT ASAR images.

Four different ENVISAT ASAR products are initially evaluated (IS2 VV, IS HH, WS HH and S4 VV). They are submitted to unsupervised semivariogram textural classification and integrated with ancillary meteorological and oceanographic data. Oceanic features observed using ENVISAT ASAR images are consistent with the wind field defined by in situ data collecting platforms and by spaceborne systems such as QuikSCAT and DMSP F-N. Whenever wind speed values are from 3.0 to 8.0 m/s, ENVISAT ASAR data provide effective enhancement of ocean surface features related to the Cantarell seepage slick. Results encourage the project team to include ENVISAT ASAR images as part of the data set to be used in Campeche Bay systematic monitoring program carried out by PEMEX Exploración and Producción.

This reliable, operational, and cost-effective joint technological initiative between Mexico, Brazil, and Canada began in 2000 and is planned to be continued for the years to come. Future developments will contemplate the combined use of RADARSAT-1, ENVISAT, and RADARSAT-2 imagery. Such a multisensor microwave data set will improve the revisit frequency in the Cantarell offshore production area. This will amount up to three images per day in southern Gulf of Mexico.

 

 

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