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Facies Trend Metrics of Modern Carbonate Depositional Systems*

Brigitte Vlaswinkel¹, Gene Rankey¹, and Paul M. (Mitch) Harris²,

Search and Discovery Article #50081 (2008)

Posted August 1, 2008

*Adapted from oral presentation at AAPG Annual Convention, Houston, Texas, April 9-12, 2006. See companion articles, "Quantifying Facies Attributes of the Caicos Platform," Search and Discovery Article #50079 (2008) and "Input for Carbonate Reservoir Models: Trend Metrics of Modern Platforms and Reef Systems," Search and Discovery Article #50127 (2008).

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.

¹University of Miami, Marine Geology and Geophysics, Miami, FL; currently Shell International E&P, Rijswijk, 2288 GS, The Netherlands ([email protected])

²Chevron Energy Technology Company, San Ramon, CA ([email protected])

Abstract

An accurate facies model is essential for realistic reservoir modeling, as depositional facies can be a main parameter controlling heterogeneity in porosity and permeability. Prediction of the quantitative attributes (size, shape, orientation, distribution, etc.) and variation of facies dimensions are also required for enhanced Multiple Point Statistics simulations for carbonate systems. To address these needs, we generated quantitative data on sizes and shapes of facies within and among different sized and shaped platforms. Landsat images from 19 modern carbonate platforms are used as analogs to offer insights into potential facies heterogeneity of carbonate systems and reservoirs.

The workflow for identifying and quantifying attributes of facies tracts included integrating literature and remote sensing images in a GIS, followed by statistical analysis. Based on objective reproducible criteria, up to 9 different facies classes were mapped and hand-digitized on all platforms, using an image analysis software program. A GIS provided a tool for quantitative characterization, measuring for every polygon of each facies attributes, such as area, perimeter, width, length, orientation, and the variability (mean, max, min) within those metrics. Subsequent statistical analyses demonstrate the existence of certain predictive “rules” between the configuration and composition of facies tracts on and among carbonate platforms (e.g., size of platform and number and abundance of facies and size of platform and shape complexity.) These kinds of “rules” provide both general concepts and raw data that can be used as input for enhanced carbonate models.

	Cross-section through Gold Spike reef complex, illustrating the major facies (left) (from Walls, 1983). Seismic profile of Malampaya (right), which is an isolated carbonate platform with a reef rim and an asymmetric facies distribution over the platform (from Grötsch and Mercadier, 1999).
	Landsat images. Glovers, Belize (left), Kalimantan (center), and South Pacific (right).
	Reef belt metrics. Circular platforms have the narrowest reef (≈230 vs 400 m). Elongate platforms have the narrowest apron (≈480 vs 800 m). Irregular platforms have the least continuous reef (≈10 km vs 14-16 km).

Conclusions

For the development geologist
- Number of faciesis independent of platform size
- Platforms have asymmetric faciesdistribution
- ‘Small’ platforms contain proportionally more potential reservoir than large platforms

· For the modeler

Trends represent predictive tools:
- Platform size and relative abundance reef
- Reef width and apron width: by shape of platform
- Reef width and orientation
“Hard”numbers for reef belt facies
- Width and variability
- Length and variability
- Aspect ratio

References

Grötsch, Jürgen, and Christophe Mercadier, 1999, Integrated 3-D reservoir modeling based on 3-D seismic: The Tertiary Malampaya and Camago buildups, offshore Palawan , Philippines : AAPG Bulletin, v. 83, p. 1703-1728.