Geochemical Significance of Gas and Gasoline-Range Hydrocarbons and Other Organic Matter in a Miocene Sample from Site 134—Balearic Abyssal Plain

Abstract

Gasoline-range hydrocarbons as well as gaseous ones are apparently seeping upward into immature, late Miocene, nonreservoir sediments in the area of Site 134 of the DSDP Leg 13 Mediterranean cruise. These conclusions are drawn from the results of geochemical analyses of a specially collected core sample. This sediment contains significant quantities of light hydrocarbons, but the rest of the organic matter appears to be so immature that it could not produce these light hydrocarbons, particularly the gasoline-range ones. Hence, the occurrence must be considered a minor but significant seepage from below. While not as spectacular as the show at Challenger Knoll (Gealy and Davies, 1969;Davis and Bray, 1969), this "show" is another indication that petroleum has already begun to form and migrate in some shallowly-buried deep-sea sediments.

Geochemistry of Upper Miocene–Lower Pliocene source rocks in the Hellenic Fold and Thrust Belt, Zakynthos Island, Ionian Sea, western Greece

“…Even though the contribution of FTBs to total world petroleum reserves is small, salt or shale associated convergence zones are related to hydrocarbon plays such as the Thrace Basin, Mediterranean Sea, South Caspian Sea and Zagros Mountains (McIver, 1973;Gürgey, 2009;Samuel et al, 2009;Morley et al, 2011;Maravelis et al, in press). Although evaporites comprise a small percentage of the sedimentary rocks, a great portion of the world's largest oil fields are sealed by salt (Grunau, 1987;Warren, 2006;Morley et al, 2011).…”

Cyclical Geochemical Properties of Organic Matter in Cariaco Basin Cores—Leg 15, Site 147

“…Organic carbon contents of most of these samples are generally very high-higher than for other sediments previously collected from deep water (Mclver, 1971); these high values reflect the silled, anaerobic conditions which apparently prevailed in this structural depression intermittently. Based on organic contents, these conditions must have existed during the deposition of the two deepest sediments we studied.…”

In Situ Formation of Petroleum in Oolites‐ Ii: A Case Study of the Arab Formation Oolite Reservoirs

“…Although the processes of hydrocarbon migration are not well-understood, many authorities on the subject are agreed that solution migration (that is, migration of hydrocarbons dissolved in formation water) may be a very prevalent mechanism (Hodgson et aL, 1964;Magara 1968Magara , 1973Magara , 1976aTissot and Welte, 1978, p.298;Hunt, 1979, pp.221-231). The history of early lithification of carbonate muds is, however, well known through the studies of Ginsburg (1957), Weller (1959), Zankl (1969), Friedman (1975) and Sayles and Manheim (1979, among others. While evidence for the early migration of hydrocarbons could be cited (Kidwell and Hunt, 1958;Gealy and Davies, 1969;McIver, 1973McIver, , 1974McIver, , 1975 the consensus of opinion is that such a phenomenon is not responsible for commercial petroleum accumulations, since the bulk of petroleum hydrocarbons are formed through thermochemical reactions at considerable depths of burial of the sediments (Sokolov et af., 1963; Philippi, 1967Philippi, , 1975Vassoeovich, 1970;Tissot et al, 1974). Presumably, also, sufficient time must be allowed in order that potential sealing beds may be deposited.…”