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19 April 2016 |   ByStephanie Ingle
Fugro Author
Just as hydrocarbon seepages on land have led to oil discoveries, so have seeps in the marine environment. Fugro is conducting the world’s largest offshore seep-hunting survey, planned to cover an area of approximately 800,000 km2.

The survey will use hull-mounted multibeam echosounder (MBES) and sub-bottom profiler systems to map the deep waters of Mexico. The data acquired will be used to identify sites where deep hydrocarbon-rich fluids are escaping to the seafloor and to target hundreds of sites for coring and geochemical analysis. The vessels Fugro Americas, Fugro Brasilis, and Fugro Gauss are being utilised for data acquisition over the course of the 18-month-long project.

Fugro Brasilis

The data collected and analysed during these specialised surveys are essential to support client decisions about where best to acquire 3D seismic data used to support exploration drilling. As a result, a seep survey is a cost-effective way of exploring frontier areas for hydrocarbon viability within a depressed oil price cycle.
Stephanie Ingle, Geoscience Consultant
Gigante hydrocarbon seep scene
Three-dimensional perspective of a hydrocarbon seep.

Gigante Seismic Survey

The seep survey carried out by Fugro for TGS is part of its industry-funded, multi-client “Gigante Survey” which includes a regional 2D seismic survey of approximately 186,000 km in the Gulf of Mexico utilising four Seabird vessels, to acquire an extensive regional grid of 2D multi-client seismic with 12,000 m offsets. Gigante will cover the vast offshore sector of Mexico, including world class producing trends such as the Perdido fold belt and Campeche Bay, and line ties will be made into the US Gulf of Mexico regional grids previously acquired by TGS. Gigante will also include gravity and magnetic data with a regional seismic structural interpretation. 

With this project TGS aims to create the most comprehensive and newest continuous offshore Mexico dataset, timed to coincide with denationalisation of Mexico’s oil and gas market, which began in 2014 after a period of seven decades of government control by state-owned Pemex.

Global Centre of Excellence

Fugro’s Global Centre of Excellence for Seep Studies in Houston ensures every seep-hunting project is consistent and performed to the same standard of excellence no matter the location. The pioneering data acquisition and interpretation methods help innovative oil companies maximise their deepwater exploration success. MBES data are processed and analysed for bathymetric, backscatter and water column anomaly information. These and sub-bottom profiler data are reported to the client typically on a daily basis. Fugro’s real-time data interpretation and analysis by experienced, onboard geoscientists provide the highest rates of both efficiency and success.

 “We create value by integrating geology, geophysics, and geotechnics data and turning it into useful information to help our clients work smarter and make better decisions faster,” explains Stephanie Ingle, Geoscience Consultant at Fugro. “The data collected and analysed during these specialised surveys are essential to support client decisions about where best to acquire 3D seismic data used to support exploration drilling. As a result, a seep survey is a cost-effective way of exploring frontier areas for hydrocarbon viability within a depressed oil price cycle.”

Backscatter calibration - a Fugro differentiator

Backscatter is one of the most important methods of remotely detecting seeps. Uncalibrated backscatter often appears as along-track bands or striping artefacts in the seafloor imagery. These artefacts are often due to offsets (gain differences) in the acoustic backscatter intensity levels between transmit sectors. It is important to normalise these acoustic offsets between sectors because they can increase the possibility of missing seafloor and water column evidence of seeps. Although much has been written about calibrating the multibeam signal for bathymetry (i.e., patch test), the backscatter signal requires its own, unique calibration, the importance of which cannot be overstated.

Did you know?

The Gigante survey project covers the entire offshore sector of Mexico - an area of approximately 625,000 square kilometres.

 

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