Page 95 - Geology of Carbonate Reservoirs

CHAPTER FOUR

STRATIGRAPHIC PRINCIPLES

This chapter is about ways in which rock and reservoir characteristics can be com-
bined to formulate geological models of carbonate reservoirs. In turn, each model
represents a geological concept on which to base exploration and development
strategies. Before the models can be mapped and exploited, and before fl ow units,

baffles, and barriers can be fully understood, the models must be put in stratigraphic
context — the larger - scale stratigraphic section and structural setting in which the
reservoir model occurs. Part of this chapter is devoted to basic principles of stratig-
raphy and sedimentology to help students understand the differences between
depositional platform types, between facies and formations, and between time, rock,
and time – rock units. Other parts focus on basic principles of stratigraphic correla-
tion and sequence stratigraphy to illustrate how individual rock and petrophysical
measurements can be placed in stratigraphic context. Finally, this chapter introduces
the concept of ideal depositional successions to set the stage for Chapter 5 , in which
ideal depositional successions are the central theme.
Finding reservoir rocks in sedimentary basins requires some knowledge about
basin architecture — the geological evolution of different basin types and the struc-
ture and arrangement of strata within them. If we know something about the struc-
ture and arrangement of stratigraphic units in basins, then we can make reasonably
accurate predictions of the sizes and shapes of carbonate reservoir bodies within
those units. Reservoir rocks only make up a small percentage of the total basin fi ll;
consequently, successful exploration and development require knowledge about
how the reservoir bodies are distributed with respect to source and seal rocks.
Basins, source rocks, reservoirs, seals, and overburden are elements in the petroleum
system as defined by Magoon and Dow (1994) . Finally, depositional rock properties

are usually altered during burial and new rock and pore characteristics are super-

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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