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Wave attenuation attributes as flow unit indicators

Southwest Research Institute, San Antonio, Texas, U.S.

Corresponding author: jparra@swri.edu

Editor's note: This article was named Best Poster Paper at SEG's 2000 Annual Meeting.

The first 20% of the full text of this article appears below.

In this article we present a model-based interpretation algorithm to predict attenuation signatures associated with a reservoir's structure and its intrinsic properties. Scattering losses are caused by multiple reflections associated with the impedance contrast between different reservoir boundaries. Intrinsic losses are due to the fluids in the reservoir, the rock fabric, and the anisotropy due to vertical fractures. Because amplitude data are sensitive to these reservoir characteristics, we calculate the wave attenuation response of the reservoir in the frequency range of surface seismic, VSP, crosswell seismic, and borehole sonic. A model of a plane wave traveling in a poroelastic multilayer earth medium allows us to include anisotropy. The multilayer part of the model simulates elastic scattering; the poroelastic part of the model simulates fluid-flow effects in the reservoir; and the anisotropic part of the model simulates reservoir fractures.

One advantage of borehole seismic measurements (including multiple-space acoustic logging, reverse VSP, VSP, and crosswell seismic) is that they can be easily related to petrophysics and core data. In acoustic logging, the source and detectors are in the same well, and the petrophysics can be directly related to acoustic attributes recorded with this single borehole tool. However, one important issue is how to relate high-resolution information based on core data and well logs with lower-resolution geophysical data. Sams (1995) addressed this problem with a processing technique that relates high-resolution well-log data (FMI) to lower-resolution acoustic logging data. The technique can also be used with crosswell high-resolution seismic data. Because these measurements require placing sources and detectors in contact with the rock formation, there is a direct relation with the petrophysics.

Borehole-scale lithology can be related to crosswell seismic measurements by a processing technique similar to that developed by Sams when reservoirs are laminated (Hackert et al., 2001). However, when the reservoir is . . . [Full Text of this Article]