We brought modern cold seep hunting to the offshore oil industry. AOA have unparalleled expertise in the design and execution of modern marine frontier prospectivity surveys using multibeam echosounder seafloor mapping,  exploration 2-D seismic data, and precision navigated geochemical coring.

Most of the major oil fields that were discovered in the early days of oil and gas exploration were traced from natural hydrocarbon seeps at the surface. The eternal flame of the ancient Zoroastrians was likely one of the multitude of natural gas seeps at Baku in the Caspian.  Many of the major fields of California, Oklahoma, Mexico, Iran, Iraq, Indonesia and elsewhere were discovered by surface hydrocarbon seeps.

Hydrocarbon seepage also occurs in the marine environment.  In 1976, Rudesindo Cantarell, a Mexican fisherman, noted the seeps that led to the discovery of the giant oil field that now bears his name.

• Evaluating frontier deepwater basins is an expensive proposition with high‑risks and high‑rewards.  Exploration teams evaluating deepwater basins need to know which concessions to pursue and which to drop.
• Modern seafloor mapping and precision geochemical sampling can quickly help teams make this decision.
• The method that we offer is inexpensive and cost effective, at $100 sq. km – about 10 times cheaper than 3-D seismic.
• With multibeam echosounders, the deeper the water, the lower the cost to acquire a 100% seafloor depth image with co-located backscatter attributes.
• The high-resolution image of the seabed acquired from a modern multibeam echosounder data can be interpreted by specialists at sea (along with previously acquired regional 2-D seismic data) for indications of seafloor seepage.
• The identified seeps are then sampled by precision-navigated piston cores.

The resulting geochemical analysis can answer critical prospectivity, source, and maturity questions from the migrated hydrocarbons that can help the exploration team assess their deepwater prospects.

Why hunt seeps?

Seafloor mapping has seen great advances during the past century, from the early days of the first echosounders such as on the FS Meteor to modern multibeam systems that can acquire data within a 5 m accuracy at over 2000 m of water depth. With attention to detail on every aspect of the acquisition system, bathymetric data can be acquired with an accuracy better than 0.5% of water depth (e.g.: 10m accuracy in 2000m of water). Accurate targeting of potential seep sites can then be sampled by navigated cores that can be located to a similar degree of accuracy, within 10 m of a target at these same depths.

The identification of seeps from remote sensing data is, in part, made possible by the hardgrounds and shelly parts of the animals that live there.

Left- Typical cold seep chemosynthetic community showing common symbionts and schematic showing upwelling hydrogen sulfide and methane. Right- Vestimentiferan tubeworm community (Cartoon modified from Dan Orange; Photo: Dan McConnell).

Identifying Seeps. We recommend two strategies for frontier prospectivity surveys. If there are only 2D exploration data, and the location of the prospects is unclear, then acquiring multibeam echosounder data can cover a large area and be used to locate seeps and sample traces of hydrocarbon leaks from the prospective basin. If there is 3D seismic data, there will be 3D images in the subsurface from which to trace potential leak paths. Precision geochemical data acquired from the first case (multibeam survey) can help determine basin prospectivity and help determine if and where to acquire 3D data. Precision geochemical data from the second case, where there is 3D seismic data, (and the first case) can help answer questions of type, age, quality and source of the hydrocarbon system.

contact Dan McConnell +1 713 532-2624

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(Images at top of page courtesy TDI-Brooks and AOA Geophysics, left, and Devon Energy for triptych at right)