Page 345 - Geology and Geochemistry of Oil and Gas

306 APPENDIX C

Cuttings Rock chips or fragments produced by drilling and
brought to the surface. Syn: Drill cuttings.
Cyanobacteria Biological/geological term for blue-green algae
(cyanophytes), the association of blue-green algae and
bacteria, or the bacterial affinity of blue-green algae.
Cyclic sedimentation Sedimentation involving a vertical repetition of rock
types representative of distinct depositional
environments. Syn: Rhythmic sedimentation.
Cycloparaffins Group of saturated homocyclic hydrocarbons having
the formula C n H 2n . Syn: Naphthene.
D
Dedolomite Dolomite that has been replaced by calcite wherein
the crystal form of the predecessor has been
preserved.
Dedolomitization Process of replacement of dolomite by calcite with
preservation of dolomite crystal form.
Deflation Removal of the loose, dry sediment by wind action.
Deflection A change in the angle of a wellbore. In directional
drilling, it is measured in degrees from the vertical.
Degrees of freedom The capability of variation in a system. The number
of degrees of freedom is determined as the number of
independent variables defining the state of a system.
Dehydration The removal of water or water vapor from gas or oil.
Delta The nearly flat alluvial tract of land at the mouth of a
river, commonly forming a triangular or fan-shaped
plain resembling the Greek letter ‘‘delta’’, D, in plan
view. It is crossed by many distributaries, and resulted
from the accumulation of sediment supplied by the
river. Most deltas are partly subaerial and partly
below water.
Deltaic Pertaining to or characterized by a delta, e.g., deltaic
sedimentation or deltaic coast.
Dendrogram A tree-like diagram depicting the mutual relationships
of a group of items sharing a common set of
variables, the variables representing either samples on
which multiple measurements have been made or
measured attributes for a group of samples.
Dendrograph A tree-like two-dimensional correlation diagram
depicting the mutual relationships between and within
groups of items sharing a common set of variables.
Density The mass or weight of a substance per unit volume (in
3
3
ppg, lb/ft , or kg/m ). Also see Specific gravity, and
API gravity.