Because of the distinctness of the type of structure that characterizes Gulf Coast salt domes and the remarkable intensity of the forces creating these features, the geology of the natural gas associated with salt domes is likewise exceptional.
Recurrence and irregularity of the upward movement of the shallow salt stocks or masses tend to divide the peripheral sands in some places into separated segments. Relatively intense movement during deposition of the sediments above or around salt domes has produced abrupt changes in the sands and later movements may have pinched out the sands against the salt. More recently discovered oil and gas fields that may be associated with very deeply buried salt masses show relatively much less deformation so that much larger deposits of gas occur.
There are only relatively small amounts of gas in most salt-dome fields in proportion to their oil. This relative scarcity of gas may be explained by the more fugitive character of gas which has permitted its escape into the atmosphere at different periods in the geologic history of the dome. The recurring periods of uplift and the creation of cracks and faults, because of their intensity, would foster such gas escapement. Commercial gas has been produced from only 7 salt-dome fields, although most of the fields have sufficient gas for local fuel needs. At present only 3 of the 68 producing salt-dome fields yield gas in quantities sufficient for use outside the field, although 4 other areas possess amounts, which, if developed, could easily supply outside commercial needs.
So few uniformly detailed analyses of coastal natural gas are available that no generalizations can be made regarding the relation of the content of coastal gases to their relation to oil on the domes, or to the position of the gases with regard to the structure.