Page 42 - Petrophysics

16 PETROPHYSICS: RESERVOIR ROCK PROPERTIES

TABLE 1.6
LIST OF TESTS FOR ROCK CHARACTERIZATION

Disaggregated Rock Particles

1. Particle size distribution by sieve analysis
2. Sphericity and roundness of the grains by microscopic analyses
3. Chemical composition of the fraction by instrumental analyses
4. Type of grains (quartz, feldspar, older rock fragments, etc.)
5. Clay mineral analyses
6. Organic content of the particle size fractions

Core Samples

1. Geologic setting and origin of the rock
2. Bedding plane orientation
3. Fluid content by retort analysis
4. Capillary pressure curves
5. Pore size distribution
6. Surface area
7. Porosity
8. Absolute permeability
9. Irreducible water saturation
10. Oil-water wettability
11. Residual oil saturation
12. Cation exchange capacity
13. Point-load strength
14. Surface mineral analyses by scanning electron microscope
15. Formation resistivity factor

Chemical sediments originate from soluble cations, particularly
sodium, potassium, magnesium, calcium, and silicon. They form beds of
evaporites with very low to zero porosity because they have a granular,
interlocking texture. Chemical sediments also serve as most of the
cementing agents for sandstones by forming thin deposits between the
rock grains.
Sedimentary particles range in size from less than one micrometer to
large boulders of several meters diameter (Table 1.7). The classification
of sizes, from boulders to clay, is indicative of their source, mode of
transportation, and hardness. Angular particles remain close to their
source of origin whereas spherical, smooth particles indicate transpor-
tation by streams. Sand, silt, and clay may be transported long distances
by water and winds. Soft carbonates will rapidly pulverize in the process
of transport, eventually being dissolved and later precipitated from
a concentrated solution.