Salt Domes

This is a very cool, imaginary graphic of a salt related feature, a salt dome, or salt diapir, that might exist along the Texas and Louisiana Gulf Coasts or in the Gulf of Mexico. Early age sediments were deposited before or during the salt extrusion. The extrusion itself caused faulting (where sediments broke due to the tectonic movement of the salt protruding upward). Some sediments were pulled upward with the salt movement and pinched out against the diaper face

Below the salt overhang is a large fault that likely offered the path for migration of evaporite minerals (salt, or halite), upwards, into overlying strata, that formed the diapir. Further away from the salt, to the left, is another fault that appears to flatten out with depth. That fault is perhaps the venue for hydrocarbon migration from deeper, organic shales that act as source beds. Oil and gas migrated up this fault plane over millions of years, spilled out into porous sediments and was trapped by other smaller faults, or was pinned against the salt wall itself. The green accumulations indicate oil in these different types of "traps."

Over time evaporite ceased to flow upwards and the top of the salt was "flattened" on top, or polished off, by sea level changes, tides and currents, etc., thus the name salt "dome." Later in geological time more sediments were deposited on top of the dome that took the form of the dome itself. The anticlinal nature of those late sediment deposits on top of the dome (the hump, so to speak) offered 4 way closure and became a trap for oil also.

This particular graphic covers a lot of neat stuff and also applies to offshore Gulf of Mexico salt domes, etc. where wells are drilled thru salt looking for hydrocarbons trapped below the salt overhang, or salt floor. This is typically called "sub-salt" exploration. The imaginary wellbore in the graphic has actually drilled to sub-salt sediments. Deep, early age Eocene Wilcox sediments offer sub salt hydrocarbon traps in the offshore areas of Louisiana and Texas. Brazil's big offshore plays are sub-salt plays.

My apologies to all my esteemed geologist friends if I messed this up. Mike