sedimentary petrology

Question 1

Define as those rocks formed from pre
existing rocks whose constituents were
transported by some mechanism.
 Most common sedimentary rocks drilled in
oilfield.
 Gravels, Sands, and Clays (i.e.
Conglomerates, Sandstones, Shales.)

Answer 1

Clastic

Question 2

Clastic Texture

Answer 2

Grain Size
 Grain Shape
 Grain Texture
 Grain Fabric
 Sphericity
 Roundness
 Grain Contact

Question 3

Grain Shape

Answer 3

Initial shape when liberated from the
original rock.
 Composition
 Hardness, brittleness, toughness, and
inherited partings.

Question 4

CALCITE CEMENTATION
TYPES:
a textural
designation denoting a situation where a
small crystal of calcium carbonate are
irregularly scattered without common
orientation in a larger crystal of another
mineral

Answer 4

Poikilotopic Crystals

Question 5

CALCITE CEMENTATION
TYPES:
in many limestones,
two distinct generations can be
distinguished, the cement that occupies
the majority of the original pore space is
clear, equant calcite, referred to as sparite,
drusy sparite or orthosparite.

Answer 5

Drusy Calcite Spar

Question 6

Implies the formation of a mineral during
or after deposition.
 Clays
 Most common authigenic clays are illite
and kaolinite.
 Positive effect if formed first, it prevents
the formation of quartz cement.

Answer 6

AUTHIGENESIS

Question 7

POROSITY AND PERMEABILITY
Three types of pore communication within
clastics:

Answer 7

 Catenary Porosity – pores communication
via 2 pore throats (effective porosity).
 Cul-de-sac Porosity – communicates via 1
throat (effective porosity).
 Closed Communications

Question 8

CARBONATE PETROLOGY
Two types of Limestone

Answer 8

 Calcite
Dolomite

Question 9

CARBONATE CEMENTATION
Main types of cement

Answer 9

 Neomorphism = recrystallization
 Miniscus Cement – micro-spar cement
found in calcilutities characterized by
irregular or curved inter-crystalline
boundary.
 Isopachous Cement – equal layers of
calcite on pre-existing grains.