Page 219 - Geology of Carbonate Reservoirs

CHAPTER EIGHT

SUMMARY: GEOLOGY OF

CARBONATE RESERVOIRS

The first three chapters in this book introduce carbonate rock and reservoir proper-
ties to set the stage for understanding the relationships between rocks and the fl uids

that move through them. A genetic classification of carbonate reservoir porosity —
depositional, diagenetic, and fracture pore types — is emphasized because fi nding
and developing carbonate reservoirs is a job of determining where porous and per-

meable rocks occur in the subsurface. Correlating flow units within fi elds then
requires understanding the geological causes that formed porosity and permeability.
Carbonate sedimentology and stratigraphy, discussed in Chapter 4 , put rocks in
temporal and spatial context to illustrate how reservoir bodies — reservoir architec-

ture — can be visualized. Chapters 5 – 7 deal specifically with depositional, diagenetic,
and fractured reservoirs.

This chapter is a summary of the discussions in the first seven chapters, it includes
some comments about methods for exploration and development in carbonate res-
ervoirs based on the author ’ s personal experience, and it includes selected fi eld
examples of the three genetic reservoir types. The purposes of this summary are to
highlight the similarities and differences between carbonate and siliciclastic reser-
voirs and between reservoir types in carbonates, and to focus on practical ways to
identify, describe, and develop carbonate reservoirs.
The fi rst rule in working carbonate reservoirs is “ look at the rocks. ” The impor-
tance of direct observation of rocks, cores, cuttings, or outcrops cannot be overem-
phasized. It is virtually impossible with present technology to identify carbonate
facies, genetic pore types, or reservoir categories based on those pore types without
direct examination of rocks. Seismic and logging methods, including data from
imaging logs and seismic attributes, cannot discriminate between carbonate pore
types, depositional facies and diagenetic facies, nor can they make 100% reliable

Geology of Carbonate Reservoirs: The Identification, Description, and Characterization of Hydrocarbon

Reservoirs in Carbonate Rocks
By Wayne M. Ahr Copyright © 2008 John Wiley & Sons, Inc.
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