Wayne D. Pennington¹, Aaron M. Green¹, Joshua I. Haataja¹

(1) Michigan Technological University, Houghton, MI

ABSTRACT: Seismic Petrophysical Modeling of Oil and Gas Production: Teal South Field, Gulf of Mexico

Teal South field, in the Gulf of Mexico, has been the location of a time-lapse seismic monitoring study through the Energy Research Clearing House. The seismic response of a reservoir can be predicted if one knows: (a) the petrophysical properties of the formation, including the compressional and shear velocities, density, and composition; (b) the evolution of the field during production, including pressure and saturation changes; and (c) the change in petrophysical properties as the field evolves. Each of these must be accurately constrained in order to obtain useful results.

At Teal South, the log data through the reservoir of interest was insufficient to fully constrain the model. We used an inversion process to obtain acoustic impedance from the pre-production seismic data, and found that the results were internally consistent with Gassmann modeling above and below the oil/water contact. Having constrained the initial model, we calculated the reservoir response under a variety of likely production scenarios and using a reasonable range of dry-frame modulus dependencies on effective pressure. Simple, straightforward assumptions can easily lead to grossly inaccurate predictions. It is essential that the investigator understand the saturation and pressure changes to be expected in the reservoir; likewise, it is critical to have developed a reliable function for the pressure-dependence of seismic velocities in the formation being studied. Only if both these conditions are met can we expect to provide accurate and useful predictions for time-lapse studies, as demonstrated at Teal South.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado