The Mexican Gulf of Mexico “Gigante” Seep Hunting Program: Unprecedented Data Quality Underpins Unprecedented Success

Abstract

In just under 1 year of continuous operations (2015-2016) 100% of the Mexican Gulf of Mexico 750m and deeper was mapped as part of the TGS “Gigante” multi-client program (total area surveyed = 477,000 km2). Datasets acquired include multibeam bathymetry, backscatter, and water column imaging as well as sub-bottom profiling (SBP). Data were also acquired in 25,400 km2 of the U.S. Alaminos Canyon protraction area to identify seep targets near known discoveries and production, and to ultimately compare seep geochemistry to reservoir, and multibeam to 3D seismic. Multibeam bathymetry data were binned at 15m, and backscatter mosaicked at 5m, independent of water depth. Water column data were evaluated for anomalies interpreted to be gas plumes. Unprecedented multibeam data quality was achieved through enhanced calibration for patch test angles, and through backscatter normalization and balancing for all sectors, pings, and modes utilized in the acquisition program. Furthermore, selected areas were surveyed with double coverage to improve backscatter resoluteness. We identified a wide range of potential seep target types, including interpreted mud volcanoes, asphalt mounds, pockmarks, fold crests, faults, high backscatter – no relief, brine lakes, and asphalt / tar flows. USBL positioned cores were acquired at over 1000 targets, including 120 sites with 20m Jumbo Piston Cores (JPC) co-located with heat flow measurement away from seep-related seafloor anomalies. Numerous interpreted gas plumes could be tied to discrete seafloor anomalies and, in some cases, to repeat SAR slicks. Other seafloor anomalies could be tied to SAR slicks without plumes, and some repeat SAR slicks occur in areas where there are no seep anomalies on the seafloor. An unprecedented percentage of oil and gas recovery was achieved, including 18% with visible oil staining. Successful oil samples retrieved TSF values higher than any previous program we're aware of (trillions of TSF units!), and, with 83% of the cores analyzed, 41% contained sufficient oil for advanced biomarker analysis and 42% qualified as strong gas hits with sufficient concentrations for isotopic analyses. We attribute the unprecedented success of the MGoM multibeam and coring program to the very high quality of multibeam data (due to enhanced calibration and backscatter normalization / balancing), quality USBL positioning, hitting the nominated targets, and the presence of active seepage in the Gulf of Mexico.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017