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Combining rock physics analysis, full waveform prestack inversion and high-resolution seismic interpretation to map lithology units in deep water

A Gulf of Mexico case study

Schlumberger Reservoir Services/Data and Consulting Services, Houston, Texas, U.S.

Marcelo Benabentos

Repsol YPF, The Woodlands, Texas, U.S.

Corresponding author: rbachrach@slb.com

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

A successful seismic-based reservoir properties estimation effort has three steps: accurate seismic inversion in 3D to obtain relevant reservoir parameters, rock physics transformation to relate reservoir parameters to the seismic parameters, and mapping these parameters in 3D. This problem is nonunique and thus any available information—specifically geologic interpretation—should be used to improve our ability to infer the reservoir properties of interest with confidence. Moreover, uncertainty associated with the different predicted values (i.e., confidence interval and estimate of misclassification probability) must be provided as well, so that proper decisions can be made. Thus, it is evident that this involves interdisciplinary effort that includes rock physics, geologic interpretation, and seismic inversion technology. However, for quantitative description of reservoir properties, one must derive a way to quantify the errors and uncertainties associated with the process.

In this paper we present a unified workflow that addresses this issue using well-known Bayesian estimation theory. The outcome of this integrated workflow is a 3D map of reservoir properties with associated probabilities and uncertainties. We illustrate this approach using an example from the deepwater Gulf of Mexico.

Recently, Mukerji et al. (GEOPHYSICS, 2001) and Avseth et al. (GEOPHYSICS, 2001) have shown how combining rock physics analysis with statistical rock physics can be used to predict lithology units and the probability of their occurrences (or, in other words, the confidence associated with the prediction). The unified workflow implemented in this case study extends their approach to propagate data/analysis from the different disciplines and integrates them to produce a reservoir properties map that reflects all known information.

Figure 1 presents a schematic diagram of the workflow. Well-log data and petrophysical analysis provide the basic input for the rock physics analysis and the generation of different lithology classes. Seismic data inverted into elastic attributes and geologic . . . [Full Text of this Article]