Oil Seeps the only real Direct Hydrocarbon Indicator

Oil Seeps – the only real Direct Hydrocarbon
Indicator

Chris Parry,
Regional and New Ventures Exploration,
E.ON Exploration & Production

[email protected]

“A look at the exploration history of the important oil areas of the world proves
conclusively that oil and gas seeps gave the first clues to most oil producing
regions. Many great oil fields are the direct result of seepage drilling.”
Link (1952).

FORCE “Underexplored Plays”, Stavanger, April 8/9th, 2015.

Presentation Outline

Hydrocarbon Seeps:
- Macroseepage,
- Microseepage.

Onshore hydrocarbon macroseepage detection:
- Seeps,
- Mud volcanoes.

Offshore hydrocarbon seepage detection:
- Mud volcanoes,
- Pockmarks,
- Gravity coring.

Summary and Conclusions

2

Exploration Success Rates – Risk Reduction

Typical Exploration Failures Most wildcat failures are due to the
fluid component of the petroleum
Seal Charge system:
(45%) (30%) - Hydrocarbon charge

Reservoir or
(15%)
- Retention
Trap
(10%)

Hydrocarbon Seepage:

Oil or gas fields emit a continuous stream of light hydrocarbon gases
to the earth's surface known as macro- and microseepages.

3

Hydrocarbon Seepage.

Macroseepage illustrate the presence of hydrocarbons Fant olje i
in a basin but may have travelled long distances, while første forsøk
microseepage travels vertically from charged reservoirs
and thus are true Direct Hydrocarbon Indicators.

Macroseepage: I mange av
- large concentrations of migrated hydrocarbons, steinprøvene fra
- visible oil staining and odour,
- migrate laterally via porous, permeable damage de utgående
zones of faults, injectites or vents, lagene på Øst-
- can be detected at the surface. Grønland kan
geologene både
Microseepage: se og lukte olje.
- chemically detectable,
- concentrations lower than macroseepage, Her er det
- no visible hydrocarbons or odour, Reidun
- migrate vertically via grain boundaries in the
rock, Myklebust i
- diagenetically altering the rocks through which TGS som gleder
they pass,
- can be detected at the surface. seg over et
«oljefunn».
4 - Det lukter olje!

Macroseepage - Oil “A look at the exploration history of the important oil areas of the

La Brea Tar Pit Museum (California) world proves conclusively that oil and gas seeps gave the first clues

to most oil producing regions. Many great oil fields are the direct
result of seepage drilling.” Link (1952).

Natural oil seeps such as these in California were exploited by the
native Americans (Achomawi and Maidu tribes) who used Asphaltum
for face painting, waterproofing boats and baskets and even chewing
gum!

The European immigrants used it to grease their wagon wheels and
later the seeps were mined by settlers, and crudely refined oil to
Oil seep McKittrick area (California) pave roads, to burn in oil lamps, and as a lubricant for machinery.

USGS: oil seep origins (1907) In the Middle East, the Dead Sea was exploited from the earliest
times. The supply of asphalt was so well known that the Romans
called it Lacus Asphaltites:

- Genesis 6:14 “make the ark with rooms, and shall cover it inside
and out with pitch”

- Genesis 11:3 “and they used brick for stone, and they used
bitumen for mortar“

- Genesis 14:10 “the Valley of Siddim was full of tar pits"

- Exodus 2:3 “she got a papyrus basket for him and coated it with
tar and pitch”

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Open pit seep mining (1850’s) By the 1850's and 60's some of the early California
Prospector mine shaft (1860’s) settlers were mining oil from natural seeps.

La Brea oil derricks (1910) The oil was mined by digging pits and tunnels at
seep sites, and, eventually, by drilling under natural
6 seeps in search of underground oil reservoirs.

Most early discoveries of oil in California were found
in this way.

Top figure: oil prospectors first mined asphaltum by
digging open pits where seeps occurred

Middle figure: This mine shaft in the McKittrick
asphaltum mine (Kern County) was built in the
1860's with redwood timbers. Oil prospectors were
often former gold miners, so they tried to use hard-
rock mining methods for extracting asphaltum and
heavy oil.

Lower figure: The Tar Pits in 1910; oil derricks can
be seen in the background

Macroseepage - Gas Mud Volcanoes are low-temperature examples of seepage
related geomorphological features and exhibit the most
Temple of Eternal Fire (Baku), 1860 spectacular evidence of subsurface fluid venting, with
powerful eruptions sometimes accompanied by flames of up
to several hundreds of meters.

Vented fluids are a complex mixture of hydrocarbon gases
(methane and wet hydrocarbons), hydrogen sulphide,
carbon dioxide, petroleum, pore waters and mud.

Comprehensive literature of numerous mud volcano
provinces demonstrate ovewhelming evidence for role of
hydrocarbon gases in their formation (biogenic and thermal
methane have different 13C content).

Direct evidence of generation, migration and
hydrocarbon potential of deeper subsurface sediments.

Lokbatan 2010 eruption (Azerbaijan)

7 Conical mud volcano: basic structure & main elements
(simplified after Dimitrov, 2002)
World’s most active mud volcano

Onshore to Offshore
1 BBOR+ Oil field area
"smelled of petroleum"

Gas bubbles – no
associated oil

8

Offshore Macroseepage Mud Volcanoes are mainly found in active accretionary
prisms or compressional settings:
Active mud volcano fluid leakage - vented fluids document subsurface petroleum systems
- mud flows often contain litho clasts of the underlying
(Black Sea)
geology (Black Sea mud volcanoes have erupted both
WD 2080m Greinert et al., 2006 the Oligo-Miocene Maikop Fm super source rock and
several different reservoir rocks).

Dredge samples Stock-on-Trent mud volcano,
(United Nations Rise, Mediterranean Sea)

(adapted and simplified after Dimitrov, 2002)

Sandstone

Active pockmark fluid leakage Shale
(Vestnesa Ridge)
Sandstone
Bünz et al., 2012
Shale
WD 1200m
Pockmarks: mainly found in unconsolidated fine-grained
9 siliciclastic setting in a wide range of tectono-stratigraphic
settings associated with structural or stratigraphic
discontinuities:

- unconformities,
- faults,
- anticlines,
- diapirs and
- shallow buried channels..

Offshore Macroseepage Detection

Surface slick Seepage mapping is much more difficult offshore
suppresses wind but has been documented off California, the Gulf of
Mexico (first described by the Spanish explorers in
ripple waves 16th century), the Labrador Sea, deepwater West
Africa (Angola, Nigeria) and the Barents Sea.
Sea surface wind
ripple waves Seafloor hydrocarbon escape features are pock

Oil coated gas marks or mud volcanoes:
bubbles

Current - Gas bubbles with oil film burst at surface
creating an oil ‘pancake’,
Bragg scatter Sustained seepage results in ‘pancakes’
from wind ripples

-

Fresnel scatter coalescing into a slick, which dampens wind
from oil film ripples and can be observed from space.

Macroseepage Synthetic Aperture Radar (SAR) is an excellent tool
Gas Chimney for detecting oil slicks and vessels:
- Covers large geographic areas,
- Independent of day light,
- Sees through cloud and fog.

LEGEND SAR can distinguish between natural occuring
seeps versus man-made pollution:
Oil coated - fresh oil is much thicker than the natural film of
gas bubble
oil associated with an active oil seep.
Pock mark

Macroseepage

Microseepage

Backgroud
seepage

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Natural Oil Seep

(click on image for video controls)

Courtesy Alan Williams, NPA Satellite Mapping, CGG 11

Natural Oil Seepage Detecting Offshore Oil Seepage

Proven low cost, high coverage
technique for exploring new
basins.

Very effective in deep and ultra
deep offhsore basins.

Reduces exploration risk on
source rock presence and
maturity.

Pollution: Fresh oil is much thicker than the natural film of oil associated with an active oil seep

Seismic evidence of hydrocarbon leakage used to design
seabed geochemical surveys

- Biological build-ups at or near sea floor:
- amplitude anomalies,
- time pull-ups,

- Mechanical disturbance of shallow sediments:
- mud volcanoes,
- pock marks,

- Diagenetic alteration of shallow sediments (Methane Derived Authigenic
Carbonates - MDACs):
- commonly carbonate precipitation,

- Shallow gas,
- Gas chimneys,
- Hydrocarbon-Related Diagenetic Zones (HRDZs),
- Rock property variations due to hydrocarbon presence (DHIs):

- bright spots,

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- flat spots.

Offshore Seep Sampling

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Gravity Piston Coring: Seafloor Geochemistry

Microseepage Gravity piston core samples:
- Grid covering prospect and background,
Background - Headspace gas analyses (C1 – C5),
- Gas Chromatography Mass Spectroscopy,
LEGEND - TOC/Rock-Eval,
Core location - Vitrinite reflectance,
Pock mark - Biostratigraphy
Macroseepage - XRD,
Microseepage - Porosity/permeability,
Backgroud - Petrography,
- SEM.
15s1e5epage
Source rock characteristics revealed by
biomarkers (fingerprinting):
- Relative abundance oil-prone vs. gas-prone

organic matter,
- age,
- environment of deposition (marine,

lacustrine, fluvio-deltaic or hypersaline),
- lithology (carbonate vs. shale vs. coal),
- thermal maturity during generation.

Calibrate basin modeling results.

Micro seepage Rate: Keta Dome Gas Storage Reservoir (Iowa)
Surface Ethane Anomalies

Saint Peter Sandstone (Ordovician) ca 300m below surface)

Empty Geochemical Charged for Winter use Empty after
Survey Grid winter use winter use

July 1988 October 1988 January 1989 April 1989

3 months (90 days) 3 months (90 days) 4 months (120 days)

Vertical movement due to gravity of gas bubbles

Migration Type?
- Buoyancy,
- Effusion (1 m/day),
- Dispersion (1 mm/year).

Keta Dome microseepage rate: between 2.5 - 3.33 m/day

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Redrawn and symplified after: Tedesco, (1999)

Summary and Conclusions

- Most of the world’s major hydrocarbon provinces are characterised by oil

seepage.

- Offshore, satellite detection of oil seepage can identify prospectivity in new

basins or identify regions to explore in areas previously dismissed as non-

productive (due to prevailing paradigms). Typical Exploration Failures
- Surface geochemical surveying can ground

truth the satellite observations. Results need

to be fully integrated into the petroleum Seal Charge
system analysis: (45%) (30%)

- Seismic interpretation and Reservoir
- Basin modeling. (15%)

Oil Seeps – the only real Trap
Direct Hydrocarbon Indicator! (10%)

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May the Source be with you!

Acknowledgements:
 E.ON management for support for this presentation,
 Alan Williams, NPA Satellite Mapping, CGG,
Jane Whaley, GeoExpro.

Bibliography

Bünz, S. & Mienert, J., 2012, Gas hydrate and shallow gas reservoirs in the
Barents Sea and on the Svalbard Margins: an unconventional resource or a
geohazard?

Carsten, H., 2012, Fant olje i første forsøk. Geo365.

Dimitrov, L.I., 2002, Mud volcanoes – the most important pathways for
degassing deeply buried sediments. Earth Sci. Rev., v.59, 49-76.

Greinert, J., Artemov, Y., Egorov, V., De Batist, M., & McGinnis, D., 2006, 1300m
high rising bubbles from mud volcanoes at 2080m in the Black Sea:
Hydroacoustic characteristics and temporal variability. Earth & Plan. Sci. Letters,
v.244, 1-15.

Link, W.R., 1952, Significance of Oil and Gas Seeps in World Oil Exploration.
AAPG., v.36(8), 1505-1540.

Tedesco, S.A., 1999, Anomaly shifts indicate rapid surface seep rates. Oil & Gas
Journal, 97 (13).

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