Two Dimensional Shallow Imaging Seismic Survey to Determine the Top of Salt at Weeks Island, Louisiana
Abstract
In the early 1990s we were contracted by Morton Salt Company to perform shallow-imaging, two dimensional seismic surveys in an attempt to determine the clastic sediment to salt interface over a portion of their mine at Weeks Island, Louisiana. Morton Salt Co. was considering mining shallow salt above their present workings and wanted to be assured that the thickness of salt required for safety existed in the area. We performed several tests over the area and collected two lines with an all terrain vehicle (ATV) mounted elastic wave generator (EWG), which is an accelerated weight drop surface seismic source. We also surveyed two test lines using one-third pound charges buried five feet. Shot and receiver spacing varied somewhat amongst the tests however the most important lines were shot with ten foot shot spacings and five foot receiver spacings with 48 channels typically yielding 12 fold data. The field data typically showed strong refraction arrivals but strong reflection arrivals only in some areas. Refraction solutions were achieved for two widely separated lines, one being near the headframe of the salt works and the other being further down over the flank of the dome in the area of main interest. Both refraction solutions indicated what we came to designate as the "7000 ft/s refractor" 50 to 100 feet below the surface. The data from only one EWG line over the area of greatest interest were processed to yield a reflection image. In the areas along this line where strong reflection arrivals were achieved these signals stacked to a strong continuous reflector at about 100 ms two-way travel time. In other areas the reflections were much weaker and discontinuous. The field data from the one-third pound charges did not contain significantly better reflection returns from any subsurface horizons than the EWG data and were not processed further.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2005
- Bibcode:
- 2005AGUSMNS21A..04K
- Keywords:
-
- 1219 Local gravity anomalies and crustal structure;
- 8105 Continental margins and sedimentary basins;
- 8015 Local crustal structure