Page 362 - Geology and Geochemistry of Oil and Gas

GLOSSARY 323
Microcrystalline See cryptocrystalline; said of a rock with such a
texture.
Microfacies Term for the features, composition, and appearance
of rocks, or of specific diagenetic features, as
identified in thin-sections.
Microspar Fabric of carbonate crystals resulting from
recrystallization of micrite-size crystals or grains that
range in size from 5 to 30 mm.
Migration The movement of liquid and gaseous hydrocarbons
from their source or generating beds, through
permeable formations into reservoir rocks.
Miscible drive Fluid displacement in which the displacing fluid and
the displaced fluid become miscible in all proportions.
Miscible mixture Complete mixture of fluids: single phase.
Mobile offshore drilling A drilling rig that is used to drill offshore exploration
unit (MODU) and development wells and that float upon the
surface of the water when being moved from one
drill site to another. Two basic types of MODUs
are used: bottom-supported drilling rig and floating
drilling rig.
Mobility The ability of a fluid to move through a reservoir.
Model An accurate simulation, by means of description,
statistical data, mathematical equation, or analogy, of
an item or process that cannot be observed directly or
that is difficult to observe directly.
Mole The fundamental unit of mass of a substance
expressed as the number of grams or pounds
indicated by its molecular weight.
Molecular weight The sum of the atomic weights in a molecule. For
example, the molecular weight of water (H 2 O) is 18
because the atomic weight of hydrogen is 1 and that
of oxygen is 16.
Monomineralic Composed of one mineral species.
Monte Carlo method A procedure in statistics employed to obtain
numerical solution to mathematical or physical
problems by means of random sampling.
Montmorillonite An expanding-lattice clay mineral, white to gray with
tints of blue, pink, and green; usually occurs in
massive, microcrystalline aggregates of very fine,
scale-like crystals. It is characterized by a three-layer
crystal lattice (one sheet of aluminum and hydroxyl
between two sheets of silicon and oxygen); subject to
swelling on wetting (and shrinking on drying) due to
introduction of considerable interlayer water. Syn:
Smectite.