The Williamson 20-13 #1 well was drilled on the flank of a
salt dome in Covington County, Mississippi. 2D seismic data
allowed for the possibility of reservoir beneath a salt
overhang at 16,000 feet. The well was drilled into salt at
approximately 10,000 feet and was still in salt at 15,000
feet, despite sidetracking. A Borehole Gravity (BHGM) survey
was run to determine the salt geometry.
Several gravity stations were made in open hole in the
salt to a depth of 15,000 feet. Other stations were made in
casing in salt and in the sediments before salt entry. The
stations in the sediments included formation tops.
A 2.5D gravity model was constructed on site during the
logging operation. The model BHGM density response (red
trace) was too low when an overhang was introduced (Figure
2.) but matched the field response (black trace) when the
model salt flank sloped slightly outward with increasing
depth. It was concluded that a salt overhang was not present
beneath the current well location. The well was subsequently
abandoned, saving further drilling expense.