Li, Yingping¹ 
(1) VSFusion, A Baker Hughes - CGG Company, Houston, TX

ABSTRACT: VSP Survey Modeling for Safe Usage of Salt Caverns

Salt caverns have been widely used for hydrocarbon storage and disposal of wastes. To safely store hydrocarbon products or wastes in a salt cavern, one must know size of the cavern and the distance from the cavern to the salt-sediment boundary. A cavern with thinner walls may collapse and result in geological disaster. Although sonar survey can measure the cavern size, it provides little information about the salt¨Csediment boundary. Drilling multiple wells to penetrate a salt dome can provide direct measurements of the salt boundary, but it costs too much. 3-D surface seismic survey can get good images for salt top, but not for steep salt flanks. In contrast, three-component vertical seismic profiling (VSP) can image the three-dimensional salt-sediment interface at the salt dome edge with much less costs. 
A newly developed 2D/3D VSP modeling package was used to conduct a series of VSP modeling studies for imaging of the salt-sediment boundary and cavern sizes. Three cases: 1) well within the cavern only, 2) well on the salt flank only, 3) wells within the cavern and on the salt flank, were studied. Both borehole seismic reflection and refraction methods were used in the modeling. Zero-offset, far-offset, walkaway VSPs, and salt proximity surveys were carried out to examine their abilities to image the salt boundary and to estimate the cavern sizes. The modeling results indicate that the VSP survey is powerful tool for imaging salt-sediment boundary and 4-D VSP survey can potentially monitor time lapse variations of the salt cavern size.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.