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Detection of Fracture Orientation Using Azimuthal Variation of P-wave AVO Responses
Maria Auxiliadora Pérez
Submitted
to the Department of Earth, Atmospheric, and Planetary Sciences on January
17, 1997 in partial fulfillment of the requirements for the degree of Doctor
of Philosophy
Abstract
Azimuthally-dependent P wave AVO (amplitude variation with offset) responses can be related to open fracture orientation and have been suggested as a geophysical tool to identify fracture orientation in fractured oil and gas reservoirs. A field experiment recently conducted over a fractured reservoir in the Barinas Basin (Venezuela) provides data for an excellent test of this approach. Three lines of data were collected in three different azimuths, and three component receivers were used. The distribution of fractures in this reservoir was previously obtained using measurements of shear wave splitting from P-S converted waves from the same dataset (Ata and Michelena, 1995). In this work, we use P-wave data to see if the data can yield the same information using azimuthal variation of P-wave AVO responses. Results obtained from the azimuthal variation of P-wave responses over the different azimuths (perpendicular and parallel to the fracture strike) using logs from nearby wells to design the earth model. The results obtained from the modeling show the same trends as the field data. This analysis with field data is an example of the high potential of P-waves to detect fracture effects on seismic wave propagation.
