Page 41 - Petrophysics

PROPERTIES OF SEDIMENTARY PARTICLES 15

TABLE 1.5
OF ROCKS DISCUSSED CHAPTER 1
GENERAL DESCRIPTIONS IN
Andesite: fine-grained extrusive igneous rock; intermediate color between
rhyolite and basalt.
Basalt: fine-grained extrusive igneous rock; dark colored.
Coquina: a form of limestone that is composed of shells and shell fragments.
Diotrite: coarse-grained intrusive igneous rock intermediate in color between
granite and gabbro; composed principally of potassium feldspar (-- 25%),
sodium plagioclase (- 35%), biotite (- 20%), and hornblend (- 20%).
Evaporite: sedimentary rock originating from the evaporation of water.
Gabbro: coarse-grained intrusive igneous rock; dark colored with an approx-
imate composition of calcium plagioclase (- 40%), augite (- 50%), and
olivine (-- 10%).
Gneiss: coarse-grained, foliated metamorphic rock. Contains feldspar and is
generally banded. The rock has recrystallized under pressure and temperature
with growth of new crystals in bands.
Granite: coarse-grained intrusive, quartz-bearing rock. The coarse texture
implies that it came from a large, slowly cooled, intrusive body and has been
exposed by uplift and deep erosion (light-colored to dark). Granite is generally
composed of a mixture of quartz (- 35%), potassium feldspar (- 45%), biotite
(- 15%), and hornblende (- 5%).
Marble: originates from metamorphosis of limestone or dolomite; the fine
crystals of limestone grow bigger and develop an interlocking texture to yield
marble.
Rhyolite (felsite): fine-grained, extrusive igneous rock; light colored.
Schist: coarse-grained, foliated, metamorphic rock containing mica; derived
from high temperature and pressure metamorphosis of shale.
Shale: fine-grained, sedimentary rock composed of clay and silt.
Slate: fine-grained, metamorphic rock derived from shale.

properties using mathematical simulation. More recent microgeometry
analyses are discussed by Ceripi et al. [14] and Talukdar and
Torsaeter [ 151.
A simplifying theme resulting from the analysis of the sources of
sedimentary rocks is that they are composed of materials from two
different sources: (1) detrital sediments are composed of discrete
particles, having a wide range of sizes, that are derived from weathering
of pre-existing rocks; (2) chemical sediments are inorganic compounds
precipitated from aqueous solutions, and may be subdivided into
carbonates and evaporites as shown in Figure 1.2. The detrital sediments
form beds of unconsolidated sands, sandstones, and shales. In the process
of being transported from the source to a depositional basin, the grains
are reduced in size and rounded, and as a result they cannot pack together
without having pore spaces between the grains.