Page 375 - Geology and Geochemistry of Oil and Gas

336 APPENDIX C

Siliciclastic In reference to terrigenous detrital sediment
composed of silicate mineral grains.
Simulation The representation of a real system by a device (such
as a computer, model, or piece of equipment) that
imitates the structure and behavior of the system.
Skewness A statistical measure of the state of asymmetry
shown by a frequency distribution curve that is
bunched on one side of the mean and tails out on
the other side.
Smectite A highly swelling family of clay minerals that includes
montmorillonite and bentonite.
Solution gas Gas dissolved so thoroughly in the crude oil that the
solution behaves as one phase. Gas bubbles dissolved
in the oil push the latter toward the wellbore.
Sonic log A type of acoustic log that records the travel time of
sounds through objects, cement, or formation rocks.
Sorting A measure of the spread or range of particle size
distribution about the mean in a sediment population.

Source rock [petrol] Sedimentary rock deposited together with the organic
material, which under pressure, heat, and time was
transformed to liquid or gaseous hydrocarbons.
Source rock is usually shale and limestone.
Source rock [sed] The rock from which fragments and other detached
pieces have been derived to form later a sedimentary
rock. Syn: Parent rock, Mother rock.
Sour gas (or crude oil) An acid gas (or crude oil) containing a significant
amount of hydrogen sulfide (H 2 S) and carbon dioxide
(CO 2 ). Cf: Sweet gas (or crude oil).
Sour gas (or oil) Gas or oil which contains hydrogen sulfide.
Spar Term for coarse crystalline calcite; commonly used in
reference to precipitated cement and may be used for
coarse crystalline, recrystallized micrite. Syn: Sparry.
Sparite Grain-supported, mud-free carbonate rock textural
type. Syn: Grainstone.
Specific heat Quantity of heat required to raise the temperature of
a unit weight of material by one degree.
Specific surface Surface of pores and pore channels per unit of pore
volume (commonly), per unit of bulk volume, or per
unit of grain volume.
Spontaneous potential Measurement of the difference in potential between
(SP) the formation and the Earth’s surface —
identification of rock types.
Spot sample Oil sample obtained from a particular level of the
tank.