Having launched the first commercially available regional interpretation of basement architecture for the Gulf last week, the firm has uncovered early rift architecture of both the onshore and offshore GoM.

Its SEEBASE study covered all the Mexico and US permit areas incorporating a hand‐contoured 3D model of the depth and geometry of the Gulf basement.

Using Frogtech's proprietary potential field geophysics interpretation process, incorporating both gravity and magnetic profile modelling, the firm was able to overcome the known challenges of mapping detailed basement architecture below the significant salt bodies that exist across the Gulf.

Frogtech principal structural geologist Dr Karen Connors told Energy News that traditionally basement had proven difficult to image on seismic data in the region due to widespread salt and the very thick post-rift sequence.

"There is so much exploration in the Gulf of Mexico and that's been known about it, but 99% of what's known is in the upper third or half of the stratigraphic section as it's only happened over a relatively short period,".

"Early exploration was focused in the shallow section, in traps generated by salt mobilisation and features.

"Then explorers started looking below the salt once acquisition and processing of seismic data gave them some better imaging of the stratigraphic section below the salt.

"But because there's so much salt and the stratigraphic section is so thick, the actual basement horizon is very difficult to image in seismic data.

"So out of that large area there's very little known about the basement surface, and the basement architecture is the container that holds the sediments and controls deposition of the sediments."

While this is an area which industry has historically known very little, it's not prospective in itself as it's simply too deep. Basement in most of the Gulf area is more 10km deep, and in some areas is up to 15-20km deep.

"So it's not a new play, but understanding the container shape is going to help you understand your sedimentary section and the petroleum systems within that container, to help look for new opportunities," Connors said.

"In the early rift system there are some big structures down there, and that will have controlled where the salt was thicker, where it was originally deposited," she said.

"That means the variations in thickness and salt will influence the salt mobilisation, which is the biggest key feature in terms of the moist productive petroleum systems in the Gulf area - both the trap development and the hydrocarbon migration."

Frogtech lists the new insights of its SEEBASE Gulf of Mexico report as:

• The hand-contoured SEEBASE model can be leveraged to understand depth to crystalline basement, rather than an automated magnetic "basement" grid (avoiding the challenges of syn-rift volcanics in some areas of the Gulf) or a base salt seismic horizon which ignores the syn-rift section;
• Identify, assess and use predictively, the relationship between interpreted crystalline basement architecture, basement structures and known hydrocarbon distribution;
• Coverage of the entire Gulf of Mexico region from the US to Mexico, highlighting the limits of the Gulf of Mexico basin system and the detailed geometry of its early rifts;
• Use the basement interpretation to assist re-evaluation of the distribution of Upper Jurassic source rocks, using the latest constraints for the extent of oceanic, transitional and extended continental crust;
• Identify potential for undiscovered hydrocarbons including the relationship between known hydrocarbon fields and basement evolution;
and
• Reduce risk away from calibration models for basin and thermal modelling, with full coverage models of present-day basement heat production and heat flow calculated from basement composition derived heat production, crustal thickness and tectonothermal history.