Regional Characterization and Classification of Salt Structures in Kingdom (Software): AAPG Webinar, September 18, 2025: Summary & Review

     Salt structures and salt tectonics are explored in this webinar. When I was an undergrad, I wrote a paper for a geophysical exploration class on hydrocarbon trapping along the Wiggins Arch in Southern Mississippi, where oil & gas were trapped in sediment accumulated along the flanks and at the crest of salt dome structures. Elemental sulfur was also a feature of the caprock there. This interesting webinar was presented by Geraldo Gaitan. Below, he shows a map of salt basins around the world and their relevance to the energy sector. 

     The Middle East and the Atlantic Margin have the best salt basins. About 50% of hydrocarbons are produced in salt basins. Salt has high thermal conductivity. Thus, heat is transferred throughout the salt structures and the surrounding rock. Salt structures have long been used to store hydrocarbons and other fluids after dissolution to make salt caverns. 

     Salt tectonics involves the study of the evolution of salt structures. Geometries can vary quite a bit: anticlines, canopies, massifs, domes, glaciers, detached salt sheets, and other structures, as shown below. Detachment structures are known as thin-skin deformation. A salt layer can pierce its overburden and generate these structures.

     Halokinesis, the movement of subsurface salt, is based on gravity. Density differences initiate salt mobilization. Sedimentation and erosion create differential loading, which can initiate halokinesis. Salt diapirs in the Netherlands are one area of study pursued by the author. The evolution of salt structures needs to be better understood. The North Sea salt tectonics and deformation are important as they affect the reservoirs and trapping. The area is also being explored for carbon sequestration, which is also based on the presence of suitable reservoirs and traps. The U.S. Gulf of Mexico is also being explored. Different tectonic events occurred in different geological time periods to affect salt movement. The Zechstein Salt is an important unit in the North Sea and Northern Europe, the base of which is a regional unconformity.

     Salt diapirs affect local tectonics in the surrounding rocks and make good places for oil & gas traps. He gives a slide of the different types of structures and their movement, including pre-diapiric, diapiric, and post-diapiric phases. Some salt structures pierce overburden rocks, and some do not. These kinematic stages are classified as follows.

     Tectonics may be active or inactive. Sediments can accumulate at the flanks of salt structures. Diapirs can also collapse, detach, and change in other ways.  

     He shows a map of the Southern North Sea Zechstein salt structures, with both concordant/non-piercing and discordant/piercing structures. He classifies them into reactive diapirism, active rise and diapirism, and passive diapirism. He shows them as a table with regional phases and local phases in time. In the North Sea, they were active in the Triassic and Cretaceous time periods. He mapped them into groups based on stages of their evolution.

     Kingdom software allows for types of faults to be mapped and modeled, including radial/concentric faults, flanking faults, and fault communication. This is important for determining salt structure trapping mechanisms and effectiveness.

 

Q&A

      Suitability for storing natural gas or hydrogen? Proximity to existing salt structures is important. It is important to have a detailed understanding of basin salt structures and geology.

     Why do some domes have caprock and others do not? He says he does not know the answer. Some geochemists say it is based on geochemistry and dissolution of the caprock. Internal deformation in salt structures and diapirs is being studied.

     Why are different faults generated on opposite sides of diapirs? Salt structures evolve asymmetrically. One flank will sometimes accumulate sediment while the other flank will not. The shape of the salt structures is a factor. Flanks can also collapse.

     He wants to apply this methodology to other basins than the failed rift basin of the Southern North Sea to more active salt basins.

     There is a question about the Campos and Santos Basins (offshore Brazil) salt structures affecting CO2 storage potential in evaporites. He does not think CO2 storage will be developed in evaporites, particularly halite. They are better for storing hydrogen and hydrocarbons rather than CO2, since CO2 may react with some evaporites.

     Question about shale diapirism. Shale intrudes via faulting, so he does not think his modeling could be used for shale diapirism.

     Anhydrite and calcite caprock have specific mechanisms for accumulating.

     Question involving rock volumetrics/accommodation of salt domes. Is there lateral compaction? Sediment accumulates adjacent to salt structures. This can cause fracturing. It depends on tectonic regimes such as extension and compaction.

     I was happy to learn more about salt structures and salt tectonics and how these subsurface processes can affect oil and gas accumulations, subsurface fluid storage, and carbon sequestration. 

 

 

  

References:

 

Extent and variability of Mesozoic- Cenozoic multi-stage salt diapirs in the Southern Permian Basin, Southern North Sea. G. Gaitan and J. Adam. Basin Research. 2023; 35:2078–2117. Gaitan & Adam Study on Salt Diapirs in S North Sea 2024.pdf