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ГЕОЛОГ УКРАЇНИ
54
Introduction
Recent studies on direct measurement and seasonal modeling of dis-
solved hydrocarbons in the Black Sea waters [4] testifies that their concentra-
tion in1.5-2 times more that it could be expected from all known and estimated
sources of man-made pollution in the basin. Therefore, there is a significant
internal source of hydrocarbons seeping from geological formations, which
points out on powerful exploration potential of the Black Sea. During last dec-
ade application of remotely sensed data acquired by synthetic aperture ra-
dar sensors installed onboard of ENVISAT, RADARSAT, ERS, JERS, ALMAZ,
TerraSAR-X, and other satellites stimulated successful exploration testifying
rather good confidence level of the technique in various shallow and deepwa-
ter petroleum-prone basins worldwide [13]. Initially, the technique was devel-
oped as environment protecting tool to monitor oil spillages, however, later on
it was found that some radar scenes can detect natural manifestations of liquid
hydrocarbon on sea surface.
This research is a continuation of the program developed at CASRE IGS
of National Academy of Sciences of Ukraine to apply space-born data for oil
and gas prospecting in the Black Sea basin [4, 8, 9]. The program includes
processing and thematic interpretation of space-born imagery coupled
with analysis of available geological, geophysical, hydrophysical, environ-
mental and meteo information. The repetitive oil slicks in two areas, west of
Tarkhankut Peninsula (Figure 1, A) and south of Cape Opuk of Crimea (known
for numerous submarine gas seeps, mud cones and pockmarks, see location
on Figure 1, B) respectively [11], allowed delineation of hydrocarbon emission
zones and selection of first-order prospects to increase success ratio in this
highly promising but still immature hydrocarbon-prone basin. This study has
shown an obvious coincidence of oil slicks repetitions with faults complicating
anticline crests and zones where tension forces dominate and stipulate inter-
mittent leakage of formation waters and hydrocarbons. However, because of
equidistant distribution of the slicks detected only two areas were preliminary
selected as promising ones.
An approach
The applied technique is based on rather simple and clear theory the prog-
nostic power of which is proved by experiments, numerical modeling and ex-
ploration practice. It is based on immanent attribute of oily material to attenuate
higher harmonics of sea waves (so-called capillary ones) due to surface ten-
sion forces of the film (Marangoni damping effect) at water-air interface. That is
why a microwave radar signal (of few cm wavelength, 5.67 for ERS-1,2) beamed
from the orbit onto a smoothed sea surface backscatters to the sensor with a
low impedance (visible dark areas) that drastically, up to 20 dB, differs from sur-
rounding wavy medium (visible light-gray background) if wind velocity ranging
from 3 to 12 m/s. That is why in case when wind fronts cross a radar scene the
oil slicks usually can be detected on their windward sides. Oil slicks form very
УДК 528.88: (553.98:551.351)](477.75)(262.5)
RADAR IMAGING APPLICATION
FOR HYDROCARBON EXPLORATION OFFSHORE
UKRAINE CASE STUDY, BLACK SEA BASIN
A. KITCHKА
Research Scientist
of CASRE IGS Nat’l Ac. Sci. Ukraine.
AAPG Team Leader
for Ukraine and EAGE Kiev
Chapter Vice-President. Awarded by
UAG Golden pin.
geolog_1_2011_new.indd 54 03.06.2011 13:43:39
№ 1, 2011 55
НАУКА: НОВІ ПОГЛЯДИ
characteristic features and patterns on sea surface and
produce peculiar semi-lunar, dogleg, spiral, snake- and
star-like structures. It is worthy to emphasize that oil slicks
are not ordinary anomalies of a radar image; first of all they
are objects because they can reflect just that matter what
explorationists are searching for.
The principle of stationarity of search features through
criterion of repetition / spatial compactness of slick popu-
lations allow delineation of hydrocarbon seeps and im-
provement of prospects ranking and assessment owing to
accumulation of useful signal. The archive series of ERS
SAR quick-looks and some georeferenced images cov-
ering the areas of interest was visualized using ENVI and
BEAM software and analyzed with ERDAS Imagine pack-
age. Further analysis was to select temporarily repetitive
slicks indicating perspective zones of higher confidence.
It was also found that vast majority of large slicks is spa-
tially coincides with the toe of the continental slope where
numerous and intensive gas seeps (or submarine gey-
sers) have been detected by sonar surveying.
Fig. 1. Areas of interest covered with SAR images (ERS satellites) for 1992-present, ESA Catalogue. A – Northwestern shelf (Pribiyna
& Albatros anticlines); B – Kerch Peninsula south offshore (Subbotina & Pionerska ones). Location of slick-derived prospects are
shown by stars
Fig. 2. Simplified geological map of Kerch Peninsula, Maykop rocks are shown in orange color
geolog_1_2011_new.indd 55 03.06.2011 13:43:40
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НАУКА: НОВІ ПОГЛЯДИ
Regional case studies
Southern shelf of Kerch Peninsula is a northern flank of
the Sorokin Trough of the circum-Black Sea basin stretch-
ing roughly along South Crimean shoreline and built by
sharp anticlines of the Maykop series verging southward
and separated by steep upthrust faults with strike-slip
component (Figure 2, and section on Figure 3).
Main prospective pay zones made by reservoir rocks in the
Maykop, Eocene and Upper Cretaceous strata. As to faults,
many of them disappear there at the bottom of Maykopian
petroliferous claystones (3500Ŝ4500m), however some ma-
jor ones go to the Mesozoic autochthonous basement (reefal
carbonates?). During Cenozoic times several tectonic pulses
have subjected the terrain including important Plio-Quater-
nary compressional/transpressional ones [10].
The latter is manifested onshore in the anticlines
pierced by shale diapirs with mud volcanoes atop and
small oil and gas-condensate fields in the Maykopian
reservoirs nearby. The area of interest there has ideal
conditions to apply remote sensing and other indirect
techniques for testing their capabilities and effective-
ness in evaluation of hydrocarbon charge of the terrain.
It is rather shallow area ranging from 20 to 90 m of water
depth. Thus, taking into account direct observations of
bubble ascending velocities determined from one of the
most thoroughly studied hydrocarbon submarine seep-
ages at Coal Oil Point, Santa Barbara Channel [1] (Fig-
ure 4) and other factors like average seasonal velocity of
local currents and dominant winds it was assumed that
detected oil slicks do not drift far away from initial emis-
sion points and generally fit to confidence area required
by such a reconnaissance study.
Slick distribution is rather equidistant and as sepa-
rate objects they do not form a compact group, except of
one over Pionerska and Lychagina anticlines (Figure 5).
Besides, many of them are significantly elongated that
speaks of stretching them by the surface water currents.
So for the moment the criterion of temporal repetition is
proved only for one particular zone of that area.
Geochemical prospecting of near-bottom concentra-
tions of methane and its proxies, helium, hydrogen and
[3] is in a good agreement with interpretation of oil slicks
derived from processing and interpretation of microwave
radar data and modeled migration paths. A comprehen-
sive analysis of all available data permits to conclude
that an optimal decision for exploration is to spud first
wildcat immediately west of actively seeping Pionerska
structure where rather thick Plio-Quarternary seal rocks
cap the eroded crest of Subbotin anticline shown on Fig-
ure 6. Later on that prediction was successfully proved
by testing of first exploration well drilled within Subbotin
prospect [6].
The latter has no manifestation of piercing by mud
diapir; therefore it could speak in favor of hydrocarbon
pools preservation. They are characterized by denser
fault network and more contrast submarine relief accord-
ing to the bathymetric map that points out on relation-
ships between recent tectonics, relief, and submarine
hydrocarbon manifestations.
As to the NW shelf the data looks much more compli-
cated due to significant pollution coming from Danube
and Dnieper rivers, accidental spills along main tanker
routes and ship lanes to Odessa, Illichivsk and Nikolaev
ports, leaks from exploration platforms and intensive al-
gal bloom during summer months. Several slick groups
of higher population density were recorded nearby
Zmeiny Island on the western part of the area studied;
however they were deselected from the consideration
for the moment due to an ambiguity caused by severe
pollution of the sea with oil products. Nevertheless, it
was possible to discriminate natural oil manifestations
from spills and confidently delineate several emission
zones, and one of them to mention is Pribiyna prospect
located west of Tarkhankut Peninsula, nearby of Krym-
ske gas field (Figure 7).
An important peculiarity of the area is a dense net-
work of latitudinal normal and reverse faults of the Gub-
kin-Tarkhankut buried deformation zone subjecting the
Fig. 3. Geological cross section [2] over the area studied, Maykop series is shown in orange color
geolog_1_2011_new.indd 56 03.06.2011 13:43:41
57
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НАУКА: НОВІ ПОГЛЯДИ
acoustic basement and the whole
sedimentary cover up to the base of
Pliocene. The section is character-
ized by presence of several lines of
undulated and upright anticlines with
elevated Cretaceous strata. The traps
in Cretaceous and Paleocene reser-
voirs are main targets of exploration
in the area under consideration. The
water depth is around 50 m here, thus
it is quite possible for JSC Chornomor-
naftogaz to use jack-ups to drill these
prospects. The radar images of this
area have demonstrated a compact
group of slicks (5 repetitions, Figure 8)
shown on ERS scenes over structures
Pribiyna, Albatros, and Martivska. Be-
sides, ASAR sensor of ENVISAT satel-
lite and OPS (very near-infrared range)
of JERS-1 one have also detected
slicks related to this emission zone.
These radar-derived prospects is in
good correspondence with interpreta-
tion maps featuring negative thermal
anomalies of sea surface caused by
seepage-driven rising of cold bottom
waters (detected by near-infrared sen-
sors of NOAA and Landsat satellites)
according to the technique developed
at CASRE [9]. It is necessary to men-
tion that Pribiyna prospect is located
not far from and in the same structural
zone as West Oktyabrske oilfield on-
shore, one of the few oil fields discov-
ered in this part of Crimea to the date
in this generally gas-prone sub-zone
of the basin. It is interesting to note
that abovenemtioned slick cluster is
coincided with southern part of an en-
igmatic ring structure (buried impact
crater?) detected by potential fields
surveying [11].
Discussion
As to the restrictions affecting ef-
fectiveness of the technique it is nec-
essary to mention that depending on
the season local sea currents vary
from ~ 5 to few tens of cm/s that could
significantly offset slicks from original
place. Other problems are related to
the lack of direct slick observations at
sea corresponded to the available im-
ages, and rather high cost of georefer-
enced radar images of full resolution.
Discrimination of natural oil slicks from
natural films and spillages is rather
Fig. 5. Natural oil slicks detected within the South Kerch offshore according to inter-
pretation of ERS SAR data for 1992-2003. Faults are shown in black, anticlines in olive
color, oil slicks are indicated as red objects, probable emission zones as blue circles
Fig. 6. An idealized model of submarine seepage, South Kerch offshore
Fig. 4. Radar-detected oil slick over La Goleta oil seep, Santa Barbara Channel, Cali-
fornia, ERS-1 image quick-look, ESA Web Catalogue
geolog_1_2011_new.indd 57 03.06.2011 13:43:42
ГЕОЛОГ УКРАЇНИ
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НАУКА: НОВІ ПОГЛЯДИ
ambiguous task. Thus, luck of direct slick observations
at sea corresponded to the available images seriously
undermines the final interpretation. Also only few com-
position analyses of submarine seeps in the Black Sea
are available to the date.
The study has demonstrated that radar imagery usu-
ally bear lots of useful information. For example, it can be
clearly distinguished some features of seawater dynam-
ics like currents, eddies, internal waves, as well as pro-
duction platforms or ships, and even jet contrails could
be recognized on radar scenes under some specific
conditions. There are indications that certain phenom-
ena like earthquakes, tides (of the solid Earth, because
usual ones are insignificant in the Black Sea) and strong
baric fronts affect or modulate submarine seepage activ-
ity and produce higher slick population density, however,
these assumptions need to be proved with proper statis-
tic retrieval of the data.
Finally, it is worth to mention that remote sensing data
has greatly improved the global assessment natural oil
discharge into oceans. Although only a few new seeps
were identified and estimates of known crude-oil fields
throughout the world have not changed greatly, new
technologies, particularly remote-sensing techniques,
have improved seep detection and assessment. The
‘best estimate’ of the global crude-oil
seepage rate was revised to 600000
mt/a, with a range of 200000 and
2000000 mt/a [7]. So there is one
important circumstance to consider:
simple calculations based on average
present-day rates (a conservative es-
timation) of hydrocarbon seepages on
sea testify that world’s conventional
oil reserves proven to this date should
disappear not later than for 1 Ma that
contradicts to conventional time laps
required by bio-organic model of pe-
troleum origin.
Conclusions
Taking into account the abovemen-
tioned one can come to the conclu-
sions as follows:
• Radar imaging is a reliable re-
mote sensing tool for offshore oil and
gas exploration based on processing
and thematic interpretation of space-
born data coupled with analysis of
available geological geophysical, hy-
drophysical and meteo information.
• The technique is based on rather
simple but quite clear theory the prog-
nostic power of which is proved by
experiments, numerical modeling and
exploration practice.
• Oil slicks are not ordinary anom-
alies of a radar image; first of all slicks
bear useful signal because they can reflect just that mat-
ter what we are searching for.
• The principle of stationarity of searching features
through criterion of repetition / spatial compactness of
slick populations allow delineation of hydrocarbon seeps
zones and improvement of prospects ranking and as-
sessment owing to steady accumulation of useful signal.
• Results of this reconnaissance study is accepted
by SGE ChornomorNaftoGaz and resulted in discovery
of Subbotin oil field.
• It was found that typical slicks are much less abun-
dant within Gulf of Odessa shelf comparing with Kerch
Peninsula southern offshore that circumstantially evi-
dences about dominant gas-prone hydrocarbon charge
of the former one.
• There is a lot of poorly understood features, proc-
esses and factors related to submarine seeps, oil slicks,
and their images on radar scenes. Much should be done
further to improve the theory and the technique.
The author acknowledges indispensable help of Va-
syl Sozansky, Marine Geology Dept., NASU, Kiev, Ira
Leifer, Univ. of California, Santa Barbara, and SGE Ukr-
Geophysika for the access to seismic data.
Fig. 7. An example of repetitive oil slicks registered over Pribiyna prospect west of
Tarkhankut Peninsula (indicated by red circle), subsets of ERS-1 SAR images, ESA
Web Catalogue
Fig. 8. Natural oil slicks detected west of Tarkhankut Peninsula according to interpreta-
tion of ERS SAR and ENVISAT ASAR images. Faults are shown in black, anticlinal crests
in yellow, oil slicks are indicated as red objects, probable emission zone is circled
geolog_1_2011_new.indd 58 03.06.2011 13:43:43
НАУКА: НОВІ ПОГЛЯДИ
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positional changes in natural gas bubble plumes: observations from the
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2. Dovzhok Ye.M., Byalyuk B.O., Ilnitsky M.K., Melnichuk P.M.
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troleum potential of the Kerch-Taman shelf, continental slope and deep-
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carbon Potential of Caspian and Black Sea Regions, 6–8 October 2008,
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7. Kvenvolden, K.A., Cooper, C.K., 2003, Estimates of the rates
at which crude oil seeps naturally into the oceans // American Asso-
ciation of Petroleum Geologists, Annual Convention, Official Program,
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8. Lyalko V.I., Pererva V.M., Kostyuchenko Yu.V. On endog-
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11. Shnyukov Ye.F., Kobolev V.P., Bogdanov Yu.A., Zakharov I.G.,
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12. Shnyukov Ye.F., Pasynkov A.A., Kleshchenko S.A. et al.,
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13. Williams A. and Lawrence G. The role of satellite seep de-
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Розглядаються переваги та обмеження застосування даних супутникових мікрохвильових радарів в морській нафтогазо-
пошуковій практиці на прикладі українського сектору Чорного моря. Встановлено, що критерій просторової повторюваності
/ компактності слікових груп дозволяє окреслювати зони підводних нафтогазопроявів і проводити ранжування акваторій
за ступенем їх перспективності через процедуру накопичення корисного сигналу та його подальшого аналізу із врахуван-
ням усіх наявних геолого-геофізичних даних. Згадана методика дозволила дати позитивний прогноз стосовно Субботінської
площі на Південнокерченському шельфі, де згодом було відкрито нафтове родовище, що довело промислову нафтогазонос-
ність Східно-Чорноморського суббасейну. Інша перспективна ділянка розташована на захід від Тарханкутського півострова,
в околі структур Прибійна, Мартівська та Альбатрос, де, попри переважно газовий стан прогнозних покладів, є всі підстави
сподіватися на відкриття нафтогазового родовища.
Рассматриваются преимущества и ограничения применения данных спутниковых микроволновых радаров в морской
нефтегазопоисковой практике на примере украинского сектора Черного моря. Установлено, что критерий пространствен-
ной повторяемости / компактности сликовых груп позволяет оконтуривать зоны подводных нефтегазопроявлений и про-
водить ранжирование акваторий по степени их перспективности посредством процедуры накопления полезного сигнала
и его дальнейшего анализа с учетом всех имеющихся геолого-геофизических данных. Указанная методика позволила дать
позитивный прогноз относительно Субботинской площади на Южнокерченском шельфе, где позже было открыто нефтя-
ное местрождение, которое доказало промышленнную нефтегазоносность Восточно-Черноморского суббасейна. Другой
перспективный участок расположен к западу от Тарханкутского полуострова, в районе структур Прибойная, Мартовская и
Альбатрос, где в преимущественно газоносном районе следует ожидать открытия нефтегазового месторождения.
Ключові слова: дистанционное зондирование, радарные космоснимки, нефтегазоносность, Черное море.
Ключевые слова: дистанційне зондування, радарні космознімки, нафтогазоносність, Чорне море.
Keywords: remote sensing, radar space-born imaging, petroleum potential, Black Sea.
geolog_1_2011_new.indd 59 03.06.2011 13:43:43
