石油の生成および進化の地化学的考察

前報油およびメタンの生成

抄録

Important source material for oil is lipid and cellulose for methane gas. All organic matters deposited in the sedimentary rocks should have been destined to be for either oil, methane gas, coal or oil shale in accordance with their chemical composition and quality.
Productive oil has been squeezed out from source sediments into porous strata in the for of "protopetroleum" emulsion. The squeeze out should have continued until the water content of the source sediments declined to 20% or the source sediments were buried 700m deep. Thereafter, the protopetroleum emulsion was transformed into real oil by low temperature thermo-energy within the porous strata. To the contrary, methane gas may have been generated in the source sediments at any time within 3 million years after their deposition.
Wax and sulfur in crude oil are intrinsical components originated from the source material.
Evolution of oil is affected by geological time and environment as follows:
(1) differentiation of oil into types through inclined reservoir rock after the accumulation,
(2) lightening of oil by precipitation of asphalts,
(3) decolorization of oil through secondary migration,
(4) changing of oil into condensate oil as the result of precipitation of heavy asphalts caused by high pressure gas invasion,
(5) production of light aromatics in oil by abnormal high pressure within the acidic pyroclastic reservoir rocks,
(6) metamorphose of oil affected by high temperature in the reservoir rocks, and
(7) oxidation of oil by invasion of rain-water resulting in the destruction of normal parafins.