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Multiple-Point Statistics (MPS)/Facies Distribution Modeling (FDM) of Carbonates – an Isolated Platform Example*

By

Marjorie Levy¹, Paul M. (Mitch) Harris¹, and Sebastien Strebelle¹

Search and Discovery Article #40292 (2008)

Posted July 30, 2008

*Adapted from oral presentation at the 2006 AAPG International Conference and Exhibition, Perth, Australia, November 5-8, 2006.

Click to view list of articles adapted from presentations by P.M. (Mitch) Harris or by his co-workers and him at AAPG meetings from 2000 to 2008.

¹ Chevron Energy Technology Company, San Ramon, California, USA (levm@chevron.com; MitchHarris@chevron.com; stsb@chevron.com)

Abstract

We have explored the use of MPS/FDM modeling in a carbonate reservoir. We have modeled the platform top of an isolated platform example and tested various scenarios for the distribution of grainstone facies.

The training image is a 3D conceptual model of the reservoir, containing information about facies dimensions and relationships among facies. Five facies were considered:

• Bar crest = best reservoir quality due to sorting in “highest energy” setting.
• Bar flank = good reservoir quality between bar crests, includes flanks of bars and intervening tidal channels.
• Island = localized areas where permeability is enhanced by dissolution during meteoric diagenesis.
• Deeper platform = poorer reservoir quality in platform areas away from bars and channels.
• Background = “tight” intervals due to muddier facies or to porosity-plugging cementation.

The facies probability cube allows controlling the spatial distribution of the facies in the MPS model. First, facies depocenter maps were generated for deeper platform, bar flank, bar crest and island. Then, the stratigraphy of the reservoir was modeled by digitizing a vertical proportion curve reflecting the variations of facies proportions with depth. Three alternative vertical proportion curves were created, representing, respectively:

• a gradual trend,
• cyclicity at the scale of composite sequences,
• high cyclicity at the scale of individual sequences.

Corresponding alternative facies probability cubes were generated for these three cases.

Several scenarios were run: the gradual, cyclic, and highly cyclic cases; both narrow and wide bar crests and bar flanks; and with constant and variable azimuth. The wide bar crest/bar flank and very cyclic simulation produce results that qualitatively appear most reasonable in both cross section and map views. Flow simulation of the various models highlights their significant differences.