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New E&P Blocks of Onshore and Offshore
Rank, Potential, Undeveloped Fields, Discoveries, and
Dry-holes
Target Exploration
TEL:
(+44) (0)2073712240
Abstract:
To speedup negotiation with the Libyan NOC we have
completed another update of our popular database review and rank of the new (early
2001) 139 offshore and onshore E&P blocks of Libya, which can be loaded on
a laptop and taken into the negotiation room.
In this study we used >666 well records, numerous
well logs, stratigraphic sections, structural sections, and stratigraphic, geochemical,
tectonic and structural maps of Cyrenaica, Ghadames, Murzuk, Sirt,
Tripolitania, and offshore basins of Libya. Due to the large number of
parameters, and to impartially assess, compare, and rank the E&P potentials
of the 139 blocks, one concession and well location map was drafted, two main
EXCEL© databases were compiled, and five subsidary EXCELÓ databases were generated to summarise well records,
exploration records, and geological, geochemical, and tectonic parameters of
the 139 new blocks:
Ø
A new well location map of the 139 Blocks (Scale 1/2500) was drafted to
illustrate the exploration or production status of the wells within the blocks.
Ø
The first E&P database lists drilling, engineering and geological
data, status and results of the 666 wells in all blocks (28*666 data entries).
One sort variation of the second database was generated to alphabetically list
wells per each block.
Ø
The second E&P database summarises the drilling, engineering and
geological data per block (31*139 data entries). An exploration risk equation
was modified to rank the relative E&P potential of the individual blocks,
via comparing the source, reservoirs, cap rocks, tectonics, remaining undrilled
anomalies, and exploration results of each block. Four sort variations of the
second database were generated in order to rank every one of the new 139
blocks, and to produce 51 charts illustrating the relative E&P ranks of the
blocks of every basin-province, the relative E&P rank of the blocks for all
basins-provinces in Libya, the relative size and distribution of the proven,
probable and possible discovered hydrocarbon reserves of all blocks, as well as
other parameters not included in the ranking equation.
1.
Introduction:
Apart from the surface stratigraphic divisions, there
are no less than 20 stratigraphic nomenclatures charts for
Published records of 666 wells (Figure 1) within the
new E&P Blocks of offshore and onshore Libya as published by the NOC in
early 2001 (Figure 2) were reviewed through this study, also a large number of
documents, well logs, cross-sections, and tectonic, stratigraphic, geochemical
and structural maps of onshore and offshore Libya as published in the Al Fateh
University series of conferences on the geology of Libya, (e.g. Wenneker et al
1996 and Ibrahim, 1992, 2000b, 2001a, 2001b).
The blocks are located -according to the Libyan NOC, in
six provinces. New block Ghadames 20 and a single large concession have
recently been delineated in the
Figure 2
After NOC 2000
The NOC’s tectonic elements map of
Table 1 Tectonic
Elements of the Main oil Provinces of Libya
1.1. Cyrenaica (Blocks
C1-C12): Inverted
Jabal 1.2. Ghadames
(Blocks G1-G20): 1.3. Murzuk
(Blocks M1-M16): 1.4. Offshore
(Blocks O1-O17): 1.5. Sirte
(Blocks S1-S70): Hon Graben, Dor Al Abd Trough, Zella Trough, Hagfa Trough, Bu Tumaym
Trough, Ajdabia Trough, Hameimat Trough, Maragh Trough, Sarir Trough and Siwa
Basin? 1.6. |
2. Geological Input
Proven source rocks of
More than 30 maps showing the regional tectonic
elements, thickness, distribution and structural configuration of source,
reservoir and cap rocks of onshore and offshore Libya were updated and used in
this study, including: large scale geological map sheets of Libya, and tectonic
elements map of Libya.
Regional structural maps includes: structural contour
map of Precambrian-Cambrian Basement rocks, structural contour map of top of
Hercynian unconformity, structural contour map of top of Mesozoic rocks,
lap-out map on top of Precambrian-Cambrian Basement.
Regional isopach maps are: isopach and facies map of
the Ordovician rocks, isopach and facies map of the Silurian rocks, isopach map
of the Devonian rocks, isopach map of the Permo-Carboniferous rocks, isopach
map of the Triassic rocks, isopach map of the Jurassic rocks, isopach map of
the Lower Cretaceous rocks, isopach map of the Upper Cretaceous rocks, facies
map of the Upper Cretaceous rocks, isopach and facies map of the Paleocene
rocks, isopach and facies map of the Eocene rocks, isopach and facies map of
the Oligocene rocks, isopach and facies map of the Miocene rocks.
Regional source rock maps used are: isopach map of
proven-possible Silurian source rocks, isopach map of probable-possible
Devonian source rocks, isopach map of proven-possible Triassic source rocks,
distribution map of proven-possible Lower Cretaceous source rocks, distribution
map of proven-possible Upper Cretaceous source rocks, and distribution map of
proven-possible Paleocene-Eocene source rocks. Added to all this geochemical
source rock analysis of Upper Cretaceous formations, and play fairway maps of
several formations.
The primary source of the above information are the
regional study the regional geology team of Sirte Oil Company (Wennekers et al.,
1996), and publications in Al Fateh University series of conferences on the
geology of Libya (such as Ibrahim 1992).
3. Using Databases to Rank E&P Blocks:
To impartially rank, and illustrate the reasons for
ranking the top most promising E&P Blocks; thirty regional source,
reservoir structural and tectonic maps of onshore and offshore
Libya were updated, and source, reservoir and seal rocks parameters, and past
exploration results of each block were listed and plotted.
The ranking of the Block was done objectively by using
a RLATIVE E&P POTENTIAL (SCORE); which is a modified risk equation,
modified to accommodate proven reserves within the blocks. This equation can be
changed should the priorities change (e.g. gas rather than oil), on the spot.
Due to the tripartite well classification of the
Libyan National Oil Corporation (Dry, Oil, Gas, with few Suspended Wells), a
new concessions map showing the location, status (dry hole, oil well, gas well
and shows) of 666 wells, undeveloped oil and gas fields, and discoveries within
the 139 new (2001) Blocks (Scale 1/2500).
Two Basic Excel Databases were compiled:
Ø
EXCELÓ Database 1: lists data, status and results of every
well in the 139 blocks as 666*28 data entries. A sort variation of this
database (Database 1A) lists the wells per each block.
Ø
EXCELÓ Database 2: summarises E&P data, exploration
histories, geological etc. and all parameters used in ranking the 139 New Block
as 139*31 data entries. Six sort variations of Database 2, which rank every one
of the new 139 blocks were used to produce 51 charts illustrating: the relative
E&P ranks of the blocks of every basin in database 2A, the proven, probable
and possibly discovered oil and gas reserves in dbase 2Bo and 2Bg for the
entire country with charts illustrating the size and distribution of the
proven, probable and possible discovered reserves of all the blocks. These sort
variations and other variations such as database 2D, and database 2E will be
discussed below.
4. Database Number 1: Wells, Undeveloped Fields, and Discoveries in the
139 New E&P Blocks of
Database
No. 1 is an Excel Database of 666*28 cells/entries (9 to 28 entries per every
one of the 666 wells in the 139 new E&P block in onshore and offshore
Libya), which summarises Target's information, as well as published technical
data on fields and wells in Libya. All information were checked for accuracy
and reliability or modified and corrected before using them in this study. The
titles of the 28 entries/well are: New (early 2001) EPSA Block, Well Name,
Longitude, Latitude, Well Number, Original Concession, Original Operator,
Location, Completion, Completion Date, TD in Meters, Formation at TD, Results.
If
the review proved that the well discovered commercial Oil and or Gas additional
entries are added: Field Name, Trap Type, Pay (s), Reservoir Lithology, Depth
of Reservoir in Meters, Net/Gross Pay Thickness, Reservoir (s) Age(s), Oil
density in °API, Reserves in MMSTBO/TCFG, Flow
Rate, Production Mechanism, Number of Wells in 1999, Number of Producing Wells,
Number of P&A Wells, Present Status of the Field/Discovery, and Comments.
4.1. Database 1A
This
is a modification of Database No. 1, in which the wells were sorted
alphabetically for each of the New E&P Blocks.
5. Database No. 2: Ranks, Relative E&P Potentials, and Undeveloped
Oil and Gas Fields and Discoveries of the 139 New E&P Blocks in Onshore and
Offshore
Database
No. 2 is an Excel database of 139*31 entries, which summarises all available
published information, and data on source facies, richness, and maturity,
reservoir rocks facies, and the structural configuration of on-and offshore
Libya. All information was checked for reliability and correctness before
synthesis.
The
titles of the 31 entries for each Block are: New (early 2001) EPSA Block,
Decimal Long. °E. of the block centre, Decimal Lat. °N.
of the block centre, Relative Prospectivity Score (RLATIVE E&P POTENTIAL
(SCORE) a modified risk equation to accommodate proven reserves, it can be
changed should priorities change, on the spot), Area of the Block in Kms 2,
Proven Oil Reserves (in MMBbls) of undeveloped fields/discoveries if present
within the block, Estimated Oil Reserves, (to quantify Probable Oil Reserves =2
MMBbls and Possible oil reserves =1 MMBbls), Proven Gas Reserves (in TCF) of
undeveloped fields/discoveries if present within the block, Estimated Gas
Reserves, (to quantify probable Gas Reserves =0.02 TCF and possible Gas
Reserves =0.01 TCF), Total Number of
Wells in the Block, Number of Discovery
and/or Suspended Wells, Number of Delineation Wells, Number of Producible
Wells. (Wells judged to be completed as a producer), Number of Wells Which Encountered
HC Shows, Number of Dry and/or Junked Wells, Kms 2/Exploration Well (Area in Sq
Km/((Total Number of Wells in the Block+1)-Delineation Wells), Discovery / Dry
holes Ratio of the Wells in the Block= 0.1+(Discovery + Suspended Wells) / (Dry
Holes-Delineation Wells). Hence, if there are no wells or there is no discovery
in the Block 0.1 was used as the average of Libya, Proven and Potential Mature
and Spent Source Rocks (by age within charging distance), Number of Proven and
Potential Source Rocks (to quantify the relative source potential), Proven and
Potential Reservoir Rocks (by age within the block), Number of Proven and
Potential Reservoir Rocks (to quantify relative reservoir availability),
Estimated Number of Undrilled Anomalies (estimate of number of anomaly in the
area - drilled wells), Estimated Maximum Size Factor of the Undrilled Anomalies
(Small (less than 100 MMBO Eq in Place)=1, Medium (>100<300 MMSTBO Eq in
Place) =1.5, and Large (>300 MMSTBO Equivalent in place)=2), Depth of Proven and/or deepest Potential
Reservoirs (in meters), Name of Nearest
Field or Discovery, Number of Nearest Fields and Discoveries, UNDEVELOPED FIELD
AND/OR DISCOVERIES WITHIN, Number of
Undeveloped Fields and Discoveries within the Block, Distance to the Nearest Oil Pipeline (in Kms
from the edge of the block), Logistics,
water depth and Terrain, Expected Hydrocarbon (from source rocks maturity and
nearby fields or fields within the block).
Database
2 is a sequential and un-sorted listing of the relative E&P potential per
basin/area; it includes relative E&P potential charts:
1.
Ranks and relative E&P potential of the new blocks of
2.
Ranks and relative E&P potential of the new blocks of Ghadames.
3.
Ranks and relative E&P potential of the new blocks of Murzuk.
4.
Ranks and relative E&P potential of the new blocks of Offshore Libya.
5.
Ranks and relative E&P potential of the top 25 new blocks of Sirte.
6.
Ranks and relative E&P potential of the middle 25 blocks of Sirte.
7.
Ranks and relative E&P potential of the last 25 blocks of Sirte.
8.
Ranks and relative E&P potential of the new blocks of
5.1. Database 2A
This
is a sort variation of Database 2, in which the new blocks of each basin were
sorted according to their relative E&P potential per basin/area. This Excel
database includes the following relative E&P potential charts:
9.
Ranks and relative E&P potential of the new blocks of
10.
Ranks and relative E&P potential of the new blocks of Ghadames.
11.
Ranks and relative E&P potential of the new blocks of Murzuk.
12.
Ranks and relative E&P potential of the new blocks of Offshore Libya.
13.
Ranks and relative E&P potential of the top 23 new blocks of Sirte.
14.
Ranks and relative E&P potential of the middle 23 blocks of Sirte.
15.
Ranks and relative E&P potential of the last 24 blocks of Sirte, shown
in figure 3.
16.
Ranks and relative E&P potential of the new blocks of
Fig. 3
5.2. Database 2Bg
This
is another sort variation of Database 2 in which the Blocks were sorted
according to their proven, probable and possible gas rather than oil reserves
in all of the 139 blocks. This variation of Database 2 includes chart:
17.
Proven, probable and possible discovered Gas Fields in all 139 new blocks,
Fig. 5
5.3. Database 2Bo
Another
sort variation of Database 2, in which the Blocks were sorted according to their
proven, probable and possible oil rather than gas reserves in all of the 139
blocks, it includes chart:
18.
Proven, probable and possible discovered Oil Fields in all 139 new blocks,
Fig. 6
5.4. Database 2C
Another
variation of Database 2, in which the Blocks were sorted according to their
relative E&P potential. This Database includes the following charts:
19.
Relative ranks and E&P Potential of the 139 new blocks,
20.
Relative E&P potential of the first 20 new blocks,
21.
Relative E&P potential of the second 20 new blocks,
22.
Relative E&P potential of the third 20 new blocks,
23.
Relative E&P potential of the fourth 20 new blocks,
24.
Relative E&P potential of the fifth 20 new blocks,
25.
Relative E&P potential of the sixth 20 new blocks,
26.
Relative E&P potential of the last 19 new blocks,
Fig. 7
27. Block area vs. relative E&P potential of the
139 new blocks,
28. Block area vs. relative E&P potential of the
139 new blocks,
29. Total number of wells vs. relative E&P
potential of the 139 new blocks,
30. Well / Kms vs. relative E&P potential of the
139 new blocks,
31. Discovery / dry hole ratio vs. relative E&P
potential of the 139 new blocks,
32. Number of remaining undrilled anomalies vs.
relative E&P potential of the 139 new blocks,
33. Average depth of primary reservoirs (in m) vs.
relative E&P potential of the 139 new blocks,
34. Distance to nearest oil pipeline vs. relative
E&P potential of the 139 new blocks,
35 Number of discovered oil and gas fields vs.
relative E&P potential of the 139 new blocks,
36. Discovered oil reserves (MMSTBIIP) within the
Blocks VS relative E&P potential of all new blocks.
37 Number of proven and potential Source Rocks vs.
relative E&P potential of the 139 new blocks,
38.
Number of proven and potential Reservoir Rocks vs. relative E&P Potential
of the 139 new blocks,
39.
Maximum size Factor of the remaining undrilled anomalies VS relative E&P
potential of the 139 new Blocks,
5.5. Database 2D
This is another variation of
Database 2C, which is showing the relative maximum size factors (MSFs) of
remaining undrilled structural anomalies (RUAs) within each Block. This was
done to highlight blocks with potential for undiscovered giant oil and gas
fields. This database includes charts:
Fig. 8
39. Relative ranks and E&P
Potential of the 139 new blocks, with the maximum sizes of the remaining
undrilled structures in each block,
40. Relative ranks and E&P
Potential of the first 20 new blocks, with the maximum sizes of the remaining
undrilled structures in each block,
41. Relative ranks and E&P
Potential of second 20 new blocks, with the maximum sizes of the remaining
undrilled structures in each block,
42. Relative ranks and E&P
Potential of the third 20 new blocks, with the maximum sizes of the remaining
undrilled structures in each block,
43. Relative ranks and E&P
Potential of the fourth 20 new blocks, with the maximum sizes of the remaining
undrilled structures in each block,
44. Relative ranks and E&P
Potential of the fifth 20 new blocks, with the maximum sizes of the remaining
undrilled structures in each block,
45. Relative ranks and E&P
Potential of the sixth 20 new blocks, with the maximum sizes of the remaining undrilled
structures in each block,
46. Relative ranks and E&P
Potential of the last 19 new blocks, with the maximum sizes of the remaining
undrilled structures in each block,
5.6. Database 2E
A
variation in plotting the Blocks of Database 2, in which the Blocks are plotted
at their central locations on a grid of decimal latitudes and longitudes. These
locations can be superimposed on the concession base map (figure 2), this
database contain charts:
47.
Location and relative E&P potential of every Block of the 139 New Blocks,
48,
Locations and number of discovered Oil and Gas fields in every Block of the 139
New Blocks,
49.
Locations and volume of discovered Oil reserves (MMSTBIIP) within the 139 New
Blocks,
50.
Locations and number of remaining undrilled anomalies (RUAs) of the 139 New
Blocks,
51.
Locations and maximum size factors (MSFs) of the remaining undrilled anomalies
of the 139 New Blocks,
Fig. 9
6. Translating the Database
into Evaluation Report, Block S25 (
Libya is like any other oil and gas-producing country had its share of
“undiscovery wells”, (Ibrahim, 2000a), hence to illustrate the importance of
critically reviewing exploration records, and versatility of the databases as
source of information as well as a ranking method; a summary of Block S25 of
Sirte Basin was compiled from the data listed in database 1 and database 2.
Fig. 11
Block S25 (Figure 2, at the
intersection of Lat. 28º N and Long. 21º E) ranks 88 among the 139 new E&P
Blocks, however it is one of the Blocks assessed to have proven, probable and
possible undeveloped discovered oil and/or gas fields and/or discoveries, figure
11.
Block S25 (about 435 Kms2.
in area) is located in southeastern
The A1-26 discovery was
delineated by two wells: A2-126 (oil well) and A3-126 (dry) both drilled to
Basement. The discovery was significant enough to merit upgrading it to field
status; hence it was named the Chadar Oil Field, a structural trap estimated to
have about 35 MMBbls of 45 ° API oil.
Other exploration wells of
Mobil within the present boundaries of Block S25 failed to encounter commercial
oil: B1-126 (junked) B1a-126 (dry), I1-126 (dry), and K1-126 (dry). Block S25
is 15 Kms from the nearest pipeline, and the field itself is 35 Kms from the
same pipeline. The exploration record of the block reflects discovery/dry ratio
of 0.15, which is above the
7. Epilogue:
Ø
Results indicate that database analysis produces an impartial ranking of
the relative E&P potentialities of a large number of blocks in several
types of basins, and can graphically illustrate the reasons for ranking the
blocks, per basin, as well as per several basins. Combined with well data
databases, a review of any of the listed blocks is also feasible.
Ø
The new offshore E&P
Blocks of Libya rank higher than the new Ghadames,
Ø
More than 19 new Blocks have
proven undeveloped oil and gas fields/oil and gas discoveries within.
Ø
Estimated total discovered oil
within the new E&P Blocks to be more than 1361 MMSTBOIIP.
Ø
More than 19 Blocks have
probable and/or possible oil and gas discoveries/oil and gas fields within.
Ø
Estimated total discovered gas
within the new E&P Blocks to be more than 0.67 TCF IIP.
Ø
Up
to 300 MMBSTB oil, or 0.4 TCF gas of proven undeveloped reserves are within
some of the “new blocks”.
Ø
Total area of the new E&P Blocks is around 1,110,200.00 Km²
Ø
Estimated
total number of remaining undrilled anomalies is around 765.
Fig. 12
Ø
There is a relationship between the relative E&P score and the
volume of proven oil reserves in the blocks where oil has been discovered, Figure
12.
Ø
High-ranking
Blocks with high maximum size factors (MSFs) of remaining undrilled anomalies
(RUAs) should be the preferential areas for future giant gas and oil
discoveries.
8. Selected
References:
Ibrahim M.W. 1992, Petroleum geology of the Sirt group Sandstones, eastern
Sirte basin. In 3rd Symposium of the Geology of Libya, 27-30 September 1987,
College of Science, Al-Fateh University, Tripoli, Libya, Vol. 7, pp 2757-2779.
Ibrahim, M.W 2000a,
Missed, By-passed, and Under-estimated Hydrocarbon Traps: Examination of Basic
Exploration Records Reveals Potential "Un-Discovery" Wells in
Ibrahim, M.W. 2000b, Rank,
Potential, Dry holes, Undeveloped Fields and Discoveries of the 97 New E&P
Blocks of Onshore and Offshore Libya, Paper Presented to MENA 2000 Oil and Gas
Conference, September 18-19, 2000, Imperial College, London, UK, 13 p.
Ibrahim, M.W., 2001a,
Rank, Potential, Undeveloped Fields and Discoveries of the 137 New E&P
Blocks of Onshore and Offshore Libya, Abstract, 2001 AAPG Annual Convention,
June 3-6, 2001,Denver, Colorado, PA97.
Ibrahim, M.W. 2001b, New
E&P Blocks of Onshore and Offshore Libya, Report and Databases, Target
Exploration, London, UK 15p, 52 figures, 7 Excel Spreadsheets and one CD-ROM.
Wennekers, J. et al. 1996,
The Geology and Hydrocarbons of the
For full list of it’s contents and to purchase your
copy:
M. Casey
Target Exploration
TEL:
(+44)(0)2073712240