Page 75 - Geology of Carbonate Reservoirs

CHAPTER THREE

PETROPHYSICAL PROPERTIES OF

CARBONATE RESERVOIRS

3.1 SATURATION, WETTABILITY, AND CAPILLARITY

This chapter covers reservoir properties and emphasizes those characteristics that
strongly correspond to fundamental rock properties enabling geologists and engi-
neers to identify rock properties that serve as proxies or “ tags ” to aid in mapping

and exploiting reservoir flow units, baffles, and barriers. Earlier, we defi ned reser-

voirs as porous and permeable bodies of rock that contain commercial quantities
of hydrocarbons. The storage capacity of a reservoir is determined by its porosity ,

the degree to which fluids can be transmitted through the reservoir is determined

by its permeability , and the pore volume filled with fluid is defined as saturation.
Wettability is the tendency for one fluid rather than another to be preferentially

attracted to a solid. Wettability depends on capillary properties of the fluids and the
solid — the phenomenon of capillarity .
3.1.1 Saturation
Saturation ( S ) is defined as the ratio of the pore volume occupied by a fl uid, nor-

mally water ( V w ), oil ( V o ), or gas ( V g ), to the total pore volume of the reservoir rock
( V p ) such that

V w
S w =
V p
V o
S o =
V p

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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