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Travel Time Inversion of Multi-Offset vertical Seismic Profilingby Submitted to the Department of Earth, Atmospheric, and Planetary Sciences on July 30, 1985 in partial fulfillment of the requirements for the degree of Master of Science ABSTRACT
A robust method of determining one-dimensional velocity structure from vertical
seismic profile travel times is formulated by the linearized least squares technique
known as Gauss’ method. Since this algorithm uses point to point ray tracing
and considers headway refractions, it is versatile enough for even wide offset
surveys. The technique is tested with synthetic data under a variety of conditions
and is found to produce good results in the presence of noise and when the horizontal
layering is improperly modeled. Three sets of field data, from Mounds , Oklahoma,
the Gulf Coast, and the Michigan Basin, were studied with this technique. The
Michigan Basin data set was especially interesting as it consisted of data from
eight source offsets ranging from 110 to 1940 m with sources azimuthally spread
about the borehole for the purpose of seismic imaging of potential reservoir.
Good agreement was found between the zero-offset VSP inversion results and velocities
from well logs. An attempt made to image the reservoir in question, a Silurian
pinnacle reef, by means of travel time residuals calculated from an average model
of the region was successful at least from a qualitative point of view. Return to Theses Return to ERL Home Updated: June, 1999
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