Studies on Origin of Petroleum: Occurrence of Hydrocarbons in Recent Sediments

Abstract

The failure of past investigators to detect liquid hydrocarbons in recent sediments has been used to support the contention that petroleum does not form in sediments at the time of deposition of the organic source material. The preferred viewpoint has visualized the eventual transformation of the original complex organic into hydrocarbons by such agencies as heat, pressure, bacteria, radioactivity, and catalysis by the sediments over indeterminate periods of time. An investigation of the nature of the organic matter deposited in recent sediments has resulted in the discovery of liquid hydrocarbons in a wide variety of salty, brackish, and fresh-water deposits. Paraffinic, naphthenic, and a variety of aromatic components have been detected. The quantity of free hydrocarbons has varied from 9-11,700 parts per million of dried sediment. Extrapolation of data obtained on two cores from the floor of the Gulf of Mexico off Louisiana, and one core from the Santa Cruz Basin off California gives estimates varying from 4,500,000 to 10,400,000 barrels of crude oil per cubic mile of sediments in these areas. The recent origin of these hydrocarbons has been established by carbon-14 analysis. Possible sources of the hydrocarbons are discussed.