APAALSE - Paper - Caris

LawrenceApaalse
ProjectCoordinator,
Ghana National Continental Shelf Delineation Project (GNCSDP)
MAKE A SPATIAL CONNECTION @ CARIS 2008
12 TH INTERNATIONAL USER GROUP CONFERENCE & EDUCATIONAL SESSIONS.
ABSTRACT
SEPTEMBER 22 – 26. BATH, UK.
The Government of Ghana instituted the National Continental Shelf Advisory Committee (NCSAC) in August 2006 under the auspices of
the Ministry of Lands, Forestry and Mines, to collate data that would justify the commissioning of the Ghana National Continental Shelf
Delineation Project (GNCSDP) in August 2007.
This paper discusses the desktop study (DTS) phase of the project. The study was carried out by Robert van de Poll of Fugro Pelagos Plc.
using the Caris Lots Software and public domain and some proprietary datasets to determine whether or not Ghana has a possible claim to an
extended continental shelf under Article 76 of the United Nations Convention on the Law of the Sea (UNCLOS). It traces the events from
the preliminary assessment of Ghana’s Article 76 initial potential of 1,440 km² to the current figure of 40,504 km², thanks to the Caris
Lots Software application.
The DTS clearly identified the 1% sediment thickness and the 350 nautical mile (M) limit as the optimal formula and constraint lines for
the delineation of the Outer Limits of the Continental Shelf (OLCS) of Ghana. It further recommends the acquisition of an extra 3,777 km
of 2D seismic data for the preparation of a comprehensive submission.
As there are no maritime boundary treaty lines within the study area, a hypothetical baseline model was generated from the World Vector
Shoreline 2 (WVS2) dataset and in some cases, using the LANSAT TM 7 14.25 meters resolution Satellite Imagery. There were also 2
small-scaled regional Nautical Charts and Orthophotos of the entire coastline.
In line with Articles 74 and 83 of UNCLOS, adjacent boundaries between Ghana and neighbouring Cote d’Ivoire, Togo, Benin and
Nigeria were also generated in the Caris Lots software using the median rule.

Introduction
Ghana signed the United Nations Convention on the Law of the Sea on Dec 10 th 1982 and
ratified it on March 20, 1983. In 1986 Ghana incorporated the UNCLOS provisions into
domestic legislation and declared the continental shelf co-extending with the Exclusive
Economic Zone (EEZ) and so pegged its outermost limits at 200 nautical miles (M) from the
Territorial Sea Baseline (TSB). With the coming into force of the Scientific and Technical
Guidelines of the Commission on the Limits of the Continental Shelf (CLCS), it became
apparent that Ghana could make a submission for the extension of the continental shelf beyond
200 M. This conviction was further motivated by the International Seabed Authority’s (ISA)
report of 2000 which indicated that Ghana has an Extended Legal Continental Shelf (ELCS)
potential of 8 billion barrels of oil equivalent.
It is important to state that, while this desktop study was carried out by Robert van de poll of
Fugro Pelagos, it has undergone dramatic transformations, including reviews by Prof. Karl Hinz,
a retired Commissioner of the CLCS, Dr. Galo Carrera and Dr. Larry Awosika, both sitting
Commissioner, and Dr. Lindsay Parson of Southampton Oceanography Centre, UK.
Establishment of the Ghana National Continental Shelf Delineation Project (GNCSDP)
In August 2006, the Minister of Lands, Forestry and Mines, put in place a National Continental
Shelf Advisory Committee (NCSAC) to oversee to all aspects of the extension of the continental
shelf of Ghana. Membership was drawn from a variety of stakeholders including the academia,
research institutions and maritime agencies. Guided by the Scientific and Technical Guidelines
and the Rules of Procedure of the CLCS, the Advisory Committee drew up a comprehensive plan
that would see Ghana undertake a desktop study for the preparation of a submission for the
extension of the continental shelf of Ghana. Consequently, the GNCSDP was commissioned on
August 30 th 2007, along with the formation of three standing Committees; the Ministerial
Oversight Committee (MOC), the Steering Committee (SC) and the Technical Core Group.
The MOC is made up of Ministers from the Ministry of Education, Science & Sports, Ministry of
Lands, Forestry & Mines, Ministry of Energy, Ministry of Foreign Affairs, Regional Integration
& NEPAD (New Partnership for Africa Development), Ministry of Justice & Attorney General
Department, Ministry of Finance & Economic Planning, Ministry of National Security, and a
representative of H. E. the President of the Republic of Ghana.
The Steering Committee and the Technical Core Group are made up of representatives from the
Geological Survey Department, Survey Department, Ghana National Petroleum Corporation
(GNPC), Ministry of Justice & Attorney General Department, Ministry of Lands, Forestry &
Mines, Ministry of Foreign Affairs, Regional Integration & NEPAD, Ministry of Finance &
Economic Planning, Regional Maritime University and the University of Ghana.
Desktop study (DTS)
The delineation of the continental shelf of any coastal State beyond 200 nautical miles and the
subsequent preparation of a submission involves several stages of scientific, legal and diplomatic
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work. The preliminary stage which normally involves scanning and desktop study is the subject
of this paper.
The preliminary assessment of data and metadata necessary for the DTS of the Ghana continental
shelf project was carried out by the Geological Survey of Denmark and Greenland (GEUS), in
consultation with NCSAC, in March 2007, using mainly seismic data supplied by the national oil
company (GNPC). The seismic, which was scanned in Kingdom Suite, revealed that the FOS
could only be located in selected areas, thus identifying some data gaps (Figure 1).
The Project later received a report prepared by Robert van de Poll, of Fugro Pelagos Inc. under
the NEPAD sponsored African Shelf Project, initiated by Senegal and the Council for
Geoscience of South Africa (CGS) using Caris Lots and public domain datasets. This assessment
includes an earlier report (Report No. 2003-0233) on preliminary continental shelf assessment of
coastal African States by Dr. S. Perritt in which Ghana was quoted as having the potential to an
Extended Legal Continental Shelf of the order of 1,440 km² based on the 1% sediment thickness
formula (Figure 2). This report which considered the area of relevance from Sierra Leone to
Gabon, assumed normal baselines from the World Vector Shoreline 2 (WVS2) database except
for Gabon where straight baselines were applied. The public domain data employed in this report
are mainly Digital Chart of the World (DCW), WVS2, 2-minute gridded bathymetry (ETOPO-2)
and the NGDC gridded sediment thickness data.
At this point, it is essential to mention that no in-house proprietary data were included in this
assessment, giving rise to the hope that the extension area could be improved with the inclusion
of these datasets. The report also conclusively recommended the Gardiner Line and the 350
nautical miles limit as the optimal formula and constraint lines respectively for Ghana.
SEISMIC DATABASE
FOS outside existing seismic
coverage, more data needed
FOS can be determined
from existing seismic data in
this region and towards the
Ivory Coast
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Figure 1: Proprietary data available in GNPC showing seismic coverage of the entire coast. The
yellow ovals are areas where the FOS could be located as mapped by GEUS &
NCSAC, March 2007.
Figure 2: This figure shows the potential extension area of 1,440 km² for Ghana (red) as depicted
in Report No. 2003-0233
The GNCSDP considers the preliminary assessment contained in Report No. 2003-0233 as the
qualifying criteria for the Test of Appurtenance (TOA) under the requirements of Article 76.
Based on this, Robert van de Poll, Fugro Pelagos, was contracted to carry out the desktop study,
in consultation with the GNCSDP, under the following scope of work:
• Define the Territorial Sea Baseline (Normal Baseline) by generating base points from UK
Hydrographic Nautical Charts, Russian Nautical Charts, recently acquired 0.5 m resolution
Orthophotos of the entire coastline of Ghana and direct Field Observations.
• Delineate adjacent boundaries between Ghana and Cote d’Ivoire, Togo, Benin and Nigeria.
• Measure the 200 nautical mile limit and the 350 M constraint line from the baseline
• Locate the FOS at the maximum change in gradient at the base of the slope.
• Choose the points where the sediment thickness is 1% of the distance to the FOS
• Determine the approximate extension area
• Recommend any extra data needs for the preparation of the submission to the CLCS
Legal Limits
The 1986 Maritime Zones (Delimitation) Law, PNDC Law 159, which incorporated the
UNCLOS provisions into Ghana’s domestic legislation, declared the following Maritime Zones
measured from the Territorial Sea Baseline (TSB):
• A Territorial Sea of 12 M,
• A Contiguous Zone of 24 M,
• An Exclusive Economic Zone (EEZ) not exceeding 200 M, and
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• A Continental Shelf of up to 200 M.
By the same legislation, the Normal Baseline was declared as the official Territorial Sea Baseline
as published in the United Nations ‘Table of Claims to Maritime Jurisdiction’, May 2008.
Territorial Sea Baseline
To proceed with the desktop study, a base map of the area (Figure 3) had to be generated. The
2006 National Geospatial Agency (NGA) WVS2 dataset was used to mimic the coastline at an
approximate scale of 1:75000 and an accuracy of ±100 m. This new NGA WVS2 dataset was
collected from present-day LANDSAT TM7 Satellite Imagery (14.25 m resolution, accuracy ±50
m, September 2003).
It must be pointed out that published base points of coastal States in the study area were not
available. However, Cote d’Ivoire and Nigeria have legal legislations for the use of both straight
and normal baselines while Togo and Benin have legislations for the use of normal baselines as
the TSB. For this reason, ‘hypothetical’ base points and baselines were produced for respective
adjacent coasts by digitizing the straight and normal baselines in Caris Lots with the help of
nautical charts, satellite imagery and orthophotos.
Strenuous efforts were made to generate base points for the Ghana TSB. Initially, two United
Kingdom Hydrographic Office Nautical Charts Nos.1383 and 1384, published on July 11, 2004
and May 12, 2005 respectively, were used. They are both regional Nautical Charts of 1:350,000
scale, showing generalized coastline with some isolated low water line information (Figure 4).
No datum was supplied for these charts and a note on the charts themselves cautions their
accuracy. Therefore, a resort was made to three larger scale Russian Nautical Charts (Chart 3500
in 1:150000, Chart 35001 in 1:150,000 and Chart 35005 in 1:50000). Recently acquired 111 0.5
m resolution orthophotos were also supplied by the Survey Department of Ghana to improve the
quality of the base points.
In the final analysis, 335 base points were computed as geographic coordinates in WGS84
Datum and are now being edited to be submitted to the United Nations for publication and also
to be used in adjacent maritime boundary delineation neighbouring coastal States (Cote d’Ivoire
to the west, and Togo, Benin and Nigeria to the east).
Out of the 335 base points, 28 were collected from the Russian Nautical Charts (see Figure 5 for
examples). The remaining 307 were collected from the Orthophotos, examples of which are
shown in figures 6 & 7.
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Figure 3: Base Map of study area showing World Vector Shoreline 2 coastline in green.
Figure 4: Example of the UKHO Nautical Charts showing the coastline at Cape Three points.
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Figure 5: Russian Nautical Charts (1:150000) of the coastline of Ghana showing low water
elevations and two base points.
Figure 6: Examples of the 0.5 meter high-resolution Orthophotos showing interpreted normal
baseline (red) and 2 base points (red dots).
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Figure 7: Examples of the 0.5 meter high-resolution Orthophotos showing interpreted normal
baselines (red) and 3 base points (red dots). In this figure, numerous offshore low
water elevations (rocks and reefs?) can clearly be seen.
Maritime Boundaries
Ghana shares maritime space with Cote d’Ivore to the West and Togo, Benin and Nigeria to the
East. Maritime boundary treaty lines (bi- or multi-lateral agreements) for these States are not
available. For this reason, the United Nations’ best practices for Law of the Sea methodologies
were followed and a “hypothetical” set of Geographic Coordinates were generated in Caris Lots
as the base points. This baseline information was then used to produce “hypothetical” maritime
boundaries between Ghana and her neighbours using the Equidistance Method (Figure 8).
Discussions are now underway with a view to signing maritime boundary treaties with Cote
d’Ivoire and Nigeria as part of the submission process. Those boundaries relating to Togo and
Benin are yet to be considered as they have not responded to Notes Verbale sent to them last
year.
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Figure 8: Diagram detailing the baselines, normal, (blue), straight (red), “hypothetical” maritime
boundary lines (orange), and the 200 M EEZ (red, offshore).
The Outer Limits of the Continental Shelf beyond 200 M
As already stated, the determination of the outer limit of the continental shelf of Ghana beyond
200 M is a straight function of the 1% sediment thickness line (which depends on the FOS) and
the 350 nautical miles constraint line.
Article 76 paragraph 4b states that “…in the absence of evidence to the contrary, the foot of the
continental slope shall be determined as the point of maximum change in the gradient at its
base...”.
Therefore, sediment thickness analysis of the sub-surface to determine the 1% sediment
thickness points relative to the Foot of the Slope (FOS) was carried out. The bathymetric echosounding
information compiled in the determination of the FOS was primarily collected from the
GEODAS database of the National Geophysical Data Center (NDGC) (Figure 9). Selected
bathymetric profiles were assembled across the continental margin of Ghana from the ETOPO2
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Digital Atlas for the purpose of illustrating the general slope morphology and selecting optimal
FOS points.
Figure 9: Result of the GEODAS database bathymetric & geophysical cruise survey search in the
Gulf of Guinea by institution source.
The FOS profile line can be drawn in the Caris Lots software. Each profile line was analyzed
using the underlying Raster bathymetric data sources (ETOPO2, and GEBCO1) and the
GEODAS ship tracks. In all, 65 lines were chosen from four different GEODAS databases to
cover the entire continental margin and the abyssal plain. The Douglas-Peucker filter from the
Caris Lots software’s ‘Foot of the Slope Tool’ which applies a linear approximation of
bathymetric profiles was applied to identify the FOS markers.
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A review of the over 700 2D SEGY lines supplied by the Ghana National Petroleum Corporation
(GNPC), showed that some of these lines could well be used to locate the FOS positions in some
areas. Unfortunately, these data were not incorporated into this study due to lack of time.
The 1% sediment thickness Formula Line (Gardiner Line)
The Caris Lots software was used to calculate the sediment thickness position at each point along
the FOS profiles and 1% sediment thickness points were determined. The individual 1%
sediment point markers were then connected together to form the 1% sediment thickness line
commonly referred to as the Gardiner Line (Figure 10).
Figure 10: The Gardiner Formula line showing SED Profile lines closely spaced yellow lines)
and the individual FOS markers (yellow and black circles). The black circles are
from the coarse-gridded sediment model.
The individual 1% sediment markers (black triangles on the yellow lines) are the individual
results of the 1% sediment positions. In this DTS, two individual sediment models were used and
these two models produced different results. The inner row of 1% sediment thickness came from
the analysis of the Fine Sediment Raster Model; the outer row of 1% sediment points came from
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the second sediment - Coarse Raster Model. It must be stated that these analyses are for
demonstration only as gridded datasets are not accepted by the Commission for submissions.
Establishment of the 350 Nautical Miles Limit
As already stated the constraint line was computed for only the 350 M as this portion of the
Eastern Equatorial Atlantic has a rather narrow continental shelf and a very steep continental
slope. The 2,500 meter isobath is very close to shore, and in no location of the study area did it
protrude seaward of the 350 M (Figure 11).
Figure 11: This figure illustrates the positions of the 2,500 m isobath (light grey line), the 2,500
m + 100 M constraint line (light green, offshore) and the 350 M line (dark blue, offshore).
Delimitation of the Potential Extension area
Based on the analyses of the two sediment datasets discussed above, two sets of results were
computed. The Fine Sediment Datasets show that Ghana’s extended continental shelf lies only to
the eastern portion of the study area with an approximate area of 6,148 km² (Figure 12).
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Figure 12: Results of the Fine Sediment Dataset showing the continental shelf extension area of
approximately 6,148 km² (red filled).
The second set of results was produced from the Coarse Sediment Datasets, which shows an
UNCLOS Article 76 extension covering the entire offshore beyond the 200 M of approximately
40,504 km² (Figure 13).
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Figure 13: This figure shows the potential UNCLOS Article 76 area of approximately 40,504
km² (red filled) based on the coarse-gridded sediment data.
Survey Planning
It has been noted that several East-West prominent linear Fracture Zones are present and very
well documented in this transform margin setting. This is critical from an analysis point of view
and for planning purposes. If these linear trends are seen to “pop through” the sediments on the
seabed, the continuity of the sediment plume seaward of the FOS, as required by CLCS, cannot
be established.
Due to these uncertainties, a multi-variate approach to seismic data planning was adopted. Two
seismic survey plans have been suggested. Plan A consists of 10 proposed lines spaced 50 M
apart with a total of 4,189 km. Survey plan B consists of 20 proposed lines, spaced at 30 M with
a total of 6,529 km. These plans were contingent on the continuity of sediments and were
designed such that the survey could be called off after a minimum of 3,777 km. These plans were
then run by Prof. Karl Hinz, courtesy the Commonwealth Secretariat, who felt that only three
seismic lines, each 300 km long, from the Ghanaian slope into the eastern potential extension
area and a maximum of three tie-lines, each about 110 km long, i.e. a total of about 1,250 km,
are sufficient (Figure 14).
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However, the GNCSDP, desirous to maximize territorial gains, has advised the government to
tender for a minimum of 2000 km that would allow for an additional strike line to test the
western corridor of our basin (Figure 14).
In line with this, several quotations have already been received, including those from SeaBird
Exploration, TGS-NOPEC, GEMS, etc. These are now being evaluated and the field work is
scheduled for November.
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Figure 14: Final seismic outline for tender. Courtesy Professor Karl Hinz.
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Conclusions and Recommendations
The results of the examinations and analyses of available public and proprietary data sources
allow the following conclusions to be made:
• Ghana can meet the test of appurtenance to extend the outer limit of the continental shelf
beyond 200 nautical miles;
• the determination of the outer limit of the continental shelf beyond 200 M is a function of
one formula line, the 1 per cent sediment thickness line, and one constraint, the 350 M line;
• the potential extended continental shelf area to the east probably overlaps with an extended
continental shelf area to which a neighbouring State, especially Nigeria, may want to lay
claim under UNCLOS. More work is required to ascertain this which would be processed as
part of the submission.
• the acquisition of some new geophysical data, in particular multi-channel seismic reflection
data appears essential in order to establish continuity of the sediments between the foot of the
slope and the outer limit points.
• in order to meet the time line of May 13, 2009 for submission, on-board processing, using the
Caris Lots and the geophysical and geological interpretation Kingdom Suite Softwares, have
been designed to simultaneously process and interprete real time data.
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BIBLIOGRAPHY
Divins, D.L., NGDC Total Sediment Thickness of the World's Oceans and Marginal Seas, Gulf
of Guinea.
http://www.ngdc.noaa.gov/mgg/sedthick/sedthick.html
GEODAS. Geodas marine geological and geophysical data from U.S. Department of Commerce,
NOAA and NGDC.
Laske, G. and G. Masters (1997). A Global Digital Map of Sediment Thickness, EOS Trans.
AGU, 78, F483.
United Nations (1999a). Scientific and Technical Guidelines of the Commission on the Limits of
the Continental Shelf. CLCS/11, 13 May 1999.
Graham Davis, 1989. Geological and Tectonic Framework of the Republic of Ghana and
Petroleum Geology of the Tano Basin, Southernwestern Ghana. Vol. 1 & 2.
Geo-Marine Letters, Vol. 17, No. 1, 1997, p1-19, 31-86
Division of Ocean Affairs and Law of the Sea Table of claims to maritime jurisdiction, May 28,
2008.
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