Changing Styles of Horizontal Salt Bodies 1984-1994

Robert O. Brooks, H. Edward Denman

Only a decade ago most salt bodies in the Gulf of Mexico were considered to be vertical piercements. New technology indicates most salt features may be detached or horizontally injected.

The first wells drilled below horizontal salt penetrated shallow pillows or thinner, laterally restricted, layered salt welds, that on seismic could be mistaken for hydrocarbon anomalies. As new 3-D seismic improved imaging of the various salt shapes, previous concepts were refined and industry focused on the lower risk features. Currently, styles range from the young allochthonous tongues of the slope to pinched off piercements of the northern shelf. Between these the southern shelf is a complex mixture of shallow pillows, thinner, deeper salt welds and winged piercements. Most of the key subsalt exploration wells in 1993-94 are located on these pillows due to good seismic visibility and lower risks. To date, primary exploration areas are from Vermilion through South Timbalier and so e areas of the upper slope.

The more extensive salt welds have not been as fully tested due to depth and uncertainty of salt thickness. Horizontal injections of the winged piercements also have not been extensively drilled primarily due to poor seismic visibility. The structural complexity of the southern shelf is due to several separate periods of salt injection, reactivation of the salt due to loading, and development of both compressional and extensional features.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995