Comparison of Acoustic Impedance and Time-amplitude Analysis Techniques for Reservoir Description of a Gulf of Mexico Shelf-edge Clastic Field

Abstract

Post-stack, time-amplitude techniques are routinely used in the estimation of reserves and the positioning of wells in low impedance, unconsolidated reservoir sands in the offshore Gulf of Mexico (Texas and Louisiana). Time amplitude analysis of 3D seismic data, when properly calibrated, can yield reliable estimates of net hydrocarbon pay, reservoir distribution, and volumetrics. Acoustic impedance (Al) analysis can also be used for such prospect appraisal and development work. However, the combined use of both techniques for reservoir description is not common. Some advantages in acoustic impedance (over amplitude analysis) are: (1) properly constrained Al traces better image the reservoir rock configuration (that is, they provide a more [open quotes]geologic[close quotes] view) thereby facilitating interpretation of reservoir distribution and interconnectivity, and (2) Al volumetrics methodology can provide more accurate estimates of average pay for reservoirs that are not seismically isolated from one another. A possible disadvantage is the difficulty in incorporating a proper baseline (low frequency) constraint for the required Al trace inversion. This paper reports the advantages and disadvantages of both techniques in characterizing net pay, volumetrics, and reservoir continuity in a producing Gulf of Mexico oil field in a shelf-edge delta depositional system.