Page 347 - Geology and Geochemistry of Oil and Gas

308 APPENDIX C

differentiated on the basis of samples from known
population.
Dispersion [stat] The extent, to which observations are dissimilar in
value, often measured by standard deviation, range,
etc.
Dispersion [petr] A suspension of extremely fine particles in a liquid
(e.g., colloids in a colloidal solution).
Dissolution Process of dissolving substances. Syn: Leaching.
Dissolution-enlargement/ In porosity studies, the process of enlarging or
enhancement otherwise enhancing the size of preexisting pores by
dissolution.
Dissolution- Common process of carbonate dissolution and void
reprecipitation formation at the microscale or macroscale, followed
by the precipitation of another mineral phase.
Distally-fining A sequence of rocks wherein sediment size decreases
either away from shore, toward deeper water
(marine), or from the point of sediment input (marine
or terrestial).
Distillation Boiling off various fractions of oil at different
temperatures.
Distribution [stat] (a) The partition of observations into intervals by
value.
(b) The set of frequencies of observations in a set of
intervals (frequency distribution).
(c) A generic term for mathematical formulae giving
probabilities related to values of random variables.
The following statistical distributions are
distinguished: binomial, chi-square, exponential, F-
distribution, geometric, hypergeometric, lognormal,
normal, Poisson, standard normal, t-distribution, etc.
Dolomite A type of sedimentary rock similar to limestone but
containing more than 50% dolomite (CaMg(CO 3 ) 2 ).
Dolomitization Replacement of preexisting carbonate sediment or
rock by dolomite.
Dolostone Synonym for dolomite rock.
Doubles Two joints of pipe (casing, tubing) fitted together.
Drawworks The hoisting equipment of a drilling rig.
Drill bit The cutting or boring element used for drilling. Syn:
Bit.
Drill collar A heavy, thick-walled tube, usually steel, used
between the drill pipe and the bit in the drillstem to
provide the pendulum effect to the drillstem and
weight to the bit.
Driller’s log Continuous recording of types of cuttings, gas, and
oil occurrences while drilling the well.