Page 378 - Geology and Geochemistry of Oil and Gas

GLOSSARY 339
interconnected and interacting elements with new,
systems properties.
T
Tar A thick black or dark brown viscous liquid obtained
by the destructive distillation of coal, wood or peat.
Telogenesis Diagenetic alteration in the subaerial meteoric
environment of rocks that once were deeply buried.
Temperature log Measurement of the formation temperature at
various depths. It is also used to determine the height
of cement behind the casing and to locate the source
of water influx into the wellbore. Syn: Temperature
survey.
Ternary diagram A triangular diagram that graphically depicts com-
position of a three-component mixture or ternary sys-
tem. The perpendicular distances of a point from each
of the three sides (in an equilateral triangle) will then
represent the relative amount of each of the materials
represented by the apexes opposite those sides.
Terrigenous Sediments, typically siliciclastic, derived from the
erosion on land of preexisting rocks. Syn: Detrital.
Tertiary recovery The production obtained by introducing a third
source of energy, i.e., enhanced oil recovery, such as
thermal, CO 2 flooding, surfactants, polymers,
alkaline flooding, in-situ combustion, and DC
electrical current.
Texture General physical appearance or characteristics of a
rock, including parameters such as size, shape,
sorting, and packing of constituent particles.
Theory of information The mathematical study of information, its storage by
codes, and its transmission through channels of
limited capacity. A fundamental idea is the entropy of
a set of events. See: Entropy, theory of information.
Thixotropy The property exhibited by a fluid that is in a liquid
state when flowing and in a semisolid, gelled state
when at rest. Most drilling fluids must be thixotropic
so that cuttings will remain in suspension when the
pipe is not in use.
Tidal flat Environment and deposits therein, formed in the
intertidal zone (including neighboring supratidal and
upper subtidal environments and deposits). Syn:
Peritidal flat.
Tight formation A petroleum- or water-bearing formation of relatively
low porosity and permeability. Syn: Hard rock.
Torque Turning or twisting force on a drilling string.