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Title: Marine oil seeps

Abstract

Petroleum hydrocarbons of both biogenic and thermogenic origin are common constituents of the marine water column and sediment of the continental shelves. Approximately 0.25 million metric tons of oil per year, constituting about 8% of the oil input into the sea, is derived from natural seeps, the rest being anthropogenic. Seepage has occurred world-wide for millions of years and must have been many times greater in the past, when enormous oil deposits, such as the Orinoco Oil Belt, were first exposed to erosion. Although the amount varies from site to site with time, seepage is pervasive in polar and temperate seas. Marine-seep oil is intensely weathered and thus can be distinguished chemically from recent biogenic or undegraded crude oil. The degraded oil from seeps appears to have little deleterious effect on many marine organisms, which ingest and discharge the oil mostly unmetabolized. Chemical analyses suggest that a very large oil-rich layer in the Sargasso Sea originated from a large and as yet undetected seep. Oil seeps have long been used as guides for oil exploration onshore but have been underutilized for this purpose offshore because of oil-plume drift from the site of the seep and because natural oil slicks maymore » be masked by spilled oil. At least one marine seep, in the Santa Barbara Channel, California, is producing oil and natural gas into two hollow steel pyramids from which the oil is collected by work boats and the natural gas is transported to shore by pipeline. This facility effectively reduces atmospheric pollution, controls marine oil pollution from the largest seep in the area, provides emission credits, and yields a modest economic benefit, but the seep is not known to have been used directly in oil exploration.« less

Authors:
 [1]
  1. (U.S. Geological Survey, Reston, VA (United States))
Publication Date:
OSTI Identifier:
7079611
Alternate Identifier(s):
OSTI ID: 7079611
Report Number(s):
CONF-910403--
Journal ID: ISSN 0149-1423; CODEN: AABUD
Resource Type:
Conference
Resource Relation:
Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States); Journal Volume: 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; CALIFORNIA; PETROLEUM DEPOSITS; GEOCHEMICAL SURVEYS; CONTINENTAL SHELF; EXPLOITATION; EXPLORATION; OFFSHORE SITES; SEAWATER; SEEPS; WATER CHEMISTRY; CHEMISTRY; CONTINENTAL MARGIN; DEVELOPED COUNTRIES; GEOLOGIC DEPOSITS; HYDROGEN COMPOUNDS; MINERAL RESOURCES; NORTH AMERICA; OXYGEN COMPOUNDS; RESOURCES; SURVEYS; USA; WATER 020200* -- Petroleum-- Reserves, Geology, & Exploration

Citation Formats

Meyer, R.F.. Marine oil seeps. United States: N. p., 1991. Web.
Meyer, R.F.. Marine oil seeps. United States.
Meyer, R.F.. Fri . "Marine oil seeps". United States. doi:.
@article{osti_7079611,
title = {Marine oil seeps},
author = {Meyer, R.F.},
abstractNote = {Petroleum hydrocarbons of both biogenic and thermogenic origin are common constituents of the marine water column and sediment of the continental shelves. Approximately 0.25 million metric tons of oil per year, constituting about 8% of the oil input into the sea, is derived from natural seeps, the rest being anthropogenic. Seepage has occurred world-wide for millions of years and must have been many times greater in the past, when enormous oil deposits, such as the Orinoco Oil Belt, were first exposed to erosion. Although the amount varies from site to site with time, seepage is pervasive in polar and temperate seas. Marine-seep oil is intensely weathered and thus can be distinguished chemically from recent biogenic or undegraded crude oil. The degraded oil from seeps appears to have little deleterious effect on many marine organisms, which ingest and discharge the oil mostly unmetabolized. Chemical analyses suggest that a very large oil-rich layer in the Sargasso Sea originated from a large and as yet undetected seep. Oil seeps have long been used as guides for oil exploration onshore but have been underutilized for this purpose offshore because of oil-plume drift from the site of the seep and because natural oil slicks may be masked by spilled oil. At least one marine seep, in the Santa Barbara Channel, California, is producing oil and natural gas into two hollow steel pyramids from which the oil is collected by work boats and the natural gas is transported to shore by pipeline. This facility effectively reduces atmospheric pollution, controls marine oil pollution from the largest seep in the area, provides emission credits, and yields a modest economic benefit, but the seep is not known to have been used directly in oil exploration.},
doi = {},
journal = {AAPG Bulletin (American Association of Petroleum Geologists); (United States)},
number = ,
volume = 75:3,
place = {United States},
year = {Fri Mar 01 00:00:00 EST 1991},
month = {Fri Mar 01 00:00:00 EST 1991}
}

Conference:
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  • This report is a synthesis of information on the marine and coastal oil seeps in Alaska, and on the effects of chronic oil pollution on Arctic marine biotic communities and ecological processes. Of 29 oil seepage areas reported along the Alaskan coast, 14 have been confirmed as containing actual oil seeps. Large areas of coastal seepage have been identified in the central Gulf of Alaska and Arctic regions. When compared to known seepage rates on the California coast, the amount of oil entering the Alaska marine environment from known coastal seeps is probably rather small. Also, the organic enrichment ofmore » the benthic communities demonstrated at California seeps might not be as evident at Arctic seeps because of slower rate of oil degradation in the latter. Additional hypotheses on the effects of natural seeps on biological communities and ecosystems are discussed.« less
  • Crude oils can be major contaminants of the marine ecosystem and microorganisms play a significant role in the degradation of the main constituents of crude oil. To increase our understanding of the microbial hydrocarbon degradation process in the marine ecosystem, we collected crude oil from an active seep area located in the Santa Barbara Channel (SBC) and generated a total of about 52 Gb of raw metagenomic sequence data. The assembled data comprised ~500 Mb, representing ~1.1 million genes derived primarily from chemolithoautotrophic bacteria. Members of Oceanospirillales, a bacterial order belonging to the Deltaproteobacteria, recruited less than 2% of themore » assembled genes within the SBC metagenome. In contrast, the microbial community associated with the oil plume that developed in the aftermath of the Deepwater Horizon (DWH) blowout in 2010, was dominated by Oceanospirillales, which comprised more than 60% of the metagenomic data generated from the DWH oil plume. This suggests that Oceanospirillales might play a less significant role in the microbially mediated hydrocarbon conversion within the SBC seep oil compared to the DWH plume oil. We hypothesize that this difference results from the SBC oil seep being mostly anaerobic, while the DWH oil plume is aerobic. Within the Archaea, the phylum Euryarchaeota, recruited more than 95% of the assembled archaeal sequences from the SBC oil seep metagenome, with more than 50% of the sequences assigned to members of the orders Methanomicrobiales and Methanosarcinales. These orders contain organisms capable of anaerobic methanogenesis and methane oxidation (AOM) and we hypothesize that these orders and their metabolic capabilities may be fundamental to the ecology of the SBC oil seep.« less
  • A belt of sea-floor oil seeps and chemosynthetic communities has been mapped across the upper continental slope, offshore Louisiana, at depths ranging from 2000 to 1000 m. Visibly oil-stained sediments and thelmogenic gas hydrates have been recovered using piston cores and research submarines. Biomarker fingerprinting of seep oils suggests an origin from deeply buried Cretaceous or Jurassic source rocks characterized by marine kerogen. The abundance of seeps provides a unique opportunity to define their relationship to oil discoveries including Auger, Cooper, Jolliet, Marquette, Vancouver, Popeye, and Mars. Seeps are preferentially distributed over shallow salt ridges that rim intrasalt basin cookingmore » pots, over salt diapirs, and along shallow fault traces near discoveries. Diagnostic seep-related features on the sea floor include gas hydrate mounds and outcrops, pockmarks and craters, mud volcanoes, and carbonate buildups. Many of the 50 chemosynthetic communities including tube worms, mussels, or clams thus far documented in the gulf occur near discoveries. Recent imagery from orbital platforms, including the space shuttle, shows that natural oil slicks are common on the sea surface in this area. Additional mapping of seep distributions should contribute to better defining of the limits of the deep Gulf play fairway.« less
  • Many Greeks believe the tarry deposits commonly observed on the beaches of Levkas, Meganissi, Cephalonia, Ithaca, and Zakinthos originate from Turkish tankers. Geologists would propose an origin from source rocks which feed the large oil pools exposed at Limni Keriou on the southwestern tip of the island of Zakinthos. Samples of this oil seep have been studied in detail, together with oil samples collected around the islands of Zakinthos, Cephalonia, Ithaca, and Meganissi, from which it can be seen a geologic origin is plausible. Examination of possible source rock intervals (for both maturity and source potential) occurring within the pre-flyschmore » succession (Triassic-Eocene) of rocks exposed in the same area has also been completed. From these findings, conjecture as to the possible source of the oil seeps has been made.« less
  • The remote-sensing literature gives ample reference to oil-seep related anomalies and their use as exploration guides. Little technical evidence has been published examining the cause-and-effect relationship between surface signature and petroleum traps. An attempt was made to detect spectral signatures (tonal and textural) related to known natural oil seeps to establish criteria for remote detection of additional seeps in frontier areas. Sites included a variety of physical settings where surface expression of geologic structure, topography, vegetation, and degree of field development were varied to determine the hypothetical potential for discovery by remote-sensing techniques. Test sites included known shallow fields inmore » Indonesia, oil sands in northern Alberta, and giant fields in the Middle East and western US. Results indicated tonal data recorded by Landsat helped discriminate possible unique (i.e. seep-related) but site-dependent signatures. SPOT 10-m resolution panchromatic data were most useful for detecting subtle textural signatures that are possibly seep related. Additional information is being analyzed, and intersite correlations between surface and sensor are being examined.« less