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.
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.
Apart from the surface stratigraphic divisions, there are no less than 20 stratigraphic nomenclatures charts for Sirte Basin alone, for almost every one of the early operating companies has one or several charts of the encountered subsurface stratigraphic units. Similar situations, though to a lesser magnitudes exist for other sedimentary basins of Libya. This E&P history produced variegated stratigraphic correlation levels, which are hard to correlate without the actual lithologic and electric logs.
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 Kufra Basin, which is now also open for exploration, (both are not shown in figure 2).
1.1. Cyrenaica (Blocks C1-C12): Inverted Jabal Akhdar Basin, Cyrenaica Platform, Marmarica Trough As-Solouq Depression.
1.2. Ghadames (Blocks G1-G20): Ghadames Basin, Al Hamra High.
1.3. Murzuk (Blocks M1-M16): Murzuk Basin, Dor El Gussa Trough and Gargaf Uplift.
1.4. Offshore (Blocks O1-O17): Sebratah Basin, Offshore Hagfa Trough, Offshore Agdabia Trough, Benghazi Basin and Offshore Al Bottnan Basin?
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. Tripolitania (Blocks T1-T3): Jeffara Trough and Zamzam Trough.
Proven source rocks of Libya were found in the Silurian, Devonian, Carboniferous, Triassic, Lower and Upper Cretaceous, Paleocene and Eocene Rocks. Proven reservoir rocks of Libya are in Basement, Ordovician, Silurian, Devonian, Carboniferous, Triassic, Cretaceous, Paleocene, Eocene and Oligocene Rocks, (Winnekers, 1996).
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).
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).
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.
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.
This is a modification of Database No. 1, in which the wells were sorted alphabetically for each of the New E&P Blocks.
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).
1. Ranks and relative E&P potential of the new blocks of Cyrenaica.
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 Tripolitania.
9. Ranks and relative E&P potential of the new blocks of Cyrenaica.
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 Tripolitania, shown in figure 4.
17. Proven, probable and possible discovered Gas Fields in all 139 new blocks, Libya, figure 5.
18. Proven, probable and possible discovered Oil Fields in all 139 new blocks, Libya, figure 6.
19. Relative ranks and E&P Potential of the 139 new blocks, Libya.
20. Relative E&P potential of the first 20 new blocks, Libya.
21. Relative E&P potential of the second 20 new blocks, Libya.
22. Relative E&P potential of the third 20 new blocks, Libya.
23. Relative E&P potential of the fourth 20 new blocks, Libya.
24. Relative E&P potential of the fifth 20 new blocks, Libya.
25. Relative E&P potential of the sixth 20 new blocks, Libya.
26. Relative E&P potential of the last 19 new blocks, Libya, figure 7.
27. Block area vs. relative E&P potential of the 139 new blocks, Libya (Area in Km2).
28. Block area vs. relative E&P potential of the 139 new blocks, Libya (Blocks).
29. Total number of wells vs. relative E&P potential of the 139 new blocks, Libya.
30. Well / Kms vs. relative E&P potential of the 139 new blocks, Libya.
31. Discovery / dry hole ratio vs. relative E&P potential of the 139 new blocks, Libya.
32. Number of remaining undrilled anomalies vs. relative E&P potential of the 139 new blocks, Libya.
33. Average depth of primary reservoirs (in m) vs. relative E&P potential of the 139 new blocks, Libya.
34. Distance to nearest oil pipeline vs. relative E&P potential of the 139 new blocks, Libya.
35 Number of discovered oil and gas fields vs. relative E&P potential of the 139 new blocks, Libya.
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, Libya.
38. Number of proven and potential Reservoir Rocks vs. relative E&P Potential of the 139 new blocks, Libya.
39. Maximum size Factor of the remaining undrilled anomalies VS relative E&P potential of the 139 new Blocks, Libya.
39. Relative ranks and E&P Potential of the 139 new blocks, with the maximum sizes of the remaining undrilled structures in each block, Libya.
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, Libya, figure 8.
41. Relative ranks and E&P Potential of second 20 new blocks, with the maximum sizes of the remaining undrilled structures in each block, Libya.
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, Libya.
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, Libya.
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, Libya.
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, Libya.
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, Libya, figure 9.
47. Location and relative E&P potential of every Block of the 139 New Blocks, Libya.
48, Locations and number of discovered Oil and Gas fields in every Block of the 139 New Blocks, Libya.
49. Locations and volume of discovered Oil reserves (MMSTBIIP) within the 139 New Blocks, Libya.
50. Locations and number of remaining undrilled anomalies (RUAs) of the 139 New Blocks, Libya.
51. Locations and maximum size factors (MSFs) of the remaining undrilled anomalies of the 139 New Blocks, Libya, figure 10.
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.
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 Sirte Basin. It is part of relinquished areas of older Concessions (Conc. 59 of Oasis Oil, and Conc. 126 of Mobil Oil Libya). There are 9 wells drilled in the sixties and early seventies which fall within the present Block boundaries, two dry holes SS1-59, and X1-59 drilled by Oasis, and 7 wells (A1, A2, A3, B1, B1a, I1, and K1-126) drilled by Mobil Oil. Mobil well A1-126 (drilled at Lt.28, 09 49 °N and Long. 20, 49 46 °E to a total depth of 3400 meters) discovered and tested commercial oil from the continental Nubian (Lower Cretaceous) sandstone at about 3000 m. below KB. Probable source rocks of the oil are the Upper Cretaceous Sirte shale and the Lower Cretaceous Nubian shale.
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 Sirte Basin average. There is probably still one more drillable anomaly in the block.
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, Cyrenaica, Sirte, Murzuk, Kufra and Tripolitania Blocks.
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 Estimated total number of remaining undrilled anomalies is around 765.
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.
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 Libya, (Abstract). AAPG Annual Convention, 16-19 April 2000, Louisiana, p. A-72.
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 Sirte Basin: A Synopsis. In Volume 1, The Geology of Sirte Basin, M. J. Salem et al, Edit, Elsevier Pub. Co. P3-56.