Since our last edition of the BPS newsletter, Crazy is as crazy does, Part 1, new information has started pouring in on Shell’s recent Graff-1 discovery, indicating that find is indeed a huge game changer for the West Africa petroleum industry (Fig. 1).
Over the last two weeks, several articles were released in the press (e.g., Reuters, Namcor, Upstream, BPS Newsletter, Ministry of Mines and Energy of Namibia and Shell) announcing the discovery of a significant 250-300mn barrel reservoir of light oil by the Graff-1 well (total depth of 5,376 meters) drilled by Shell at a water depth of 1,900 meters in Block 2913A of the Orange sub-basin (Fig. 1). Meanwhile, Wood Mackenzie goes so far as to estimate around 700mn barrels of recoverable oil, mentioning that this would be Shell’s largest commercial find in Sub-Saharan Africa since Bonga in 1996. The oil was found in two Cretaceous sandstone turbidite targets. Not too shabby for Namibia’s first ever commercial oil discovery!!!
Since the breaking of the gas paradigm in 2013 by HRT Petroleum (today PetroRio), which found light oil (e.g., 31o API) in Albian sandstone turbidites in the Wingat-1 well (Fig. 1), most of the oil majors have taken note and started to look at Namibia with fresh eyes. In the year since, Shell, Galp, Total, ExxonMobil, Tullow and Qatar Energy, among others, have all acquired deep-water blocks in the Walvis and Orange basins.
After drilling three of the four intended deep-water wells in Namibia, namely Wingat-1, Murombe-1 and Moosehead-1 in the offshore Walvis & Orange basins, the results indicated the presence of multiple marine and lacustrine overcharged source rock systems (Figs. 1 and 2; Mello et al., 2012, 2014 and 2015). The most important among them were the Albo-Aptian (e.g., marine restricted black shales of the Kudu Formation) and Barremian (e.g., lacustrine brackish to saline black shales) systems (e.g., Fig. 2; Mello et al., 2012, 2014 and 2015).
More importantly, both systems identified in the Walvis and Orange basins were sourced from the same oil types as the ones found in the giant Santos and Campos Basins in Brazil (Fig. 3; Mello et al., 2011, 2012, 2014 and 2015). Meanwhile, gas occurrences resulting from high maturity levels of the marine and lacustrine source facies were collected and analyzed, showing several stages of oil and gas cracking and suggesting very high thermal evolution, which is favorable for generation, expulsion and migration of significant volumes of oil and gas, but also indicating a mainly light oil/condensate prone petroleum system (Fig. 4; Mello et al., 2012, 2014 and 2015).
Regarding reservoir systems, the presence of upper Cretaceous carbonates and upper to lower Cretaceous turbidite sandstone reservoirs were indicated in both HRT’s Murombe-1 and Shell’s Graff-1 wells, presenting very good permoporosity characteristics (Fig. 5 Mello et al., 2012, 2014 and 2015). Moreover, the drilled prospects and seismic interpretation in the blocks in the vicinity of Shell’s Block 2913A identified a huge number of structural, stratigraphic and mixed (structural/stratigraphic) leads and prospects with prospective resources in the billions of barrels (Fig. 6; Mello et al., 2012, 2014 and 2015).
Figure 7 illustrates a preliminary 3D petroleum system model of the Aptian to Barremian source rock interval of transgressive black shales from the Kudu Formation and the lacustrine Barremian source rocks in the western and northern portions of the Orange Basin in southern Namibia (taken from Mello et al., 2014 and 2015). Note the 3D petroleum system modeling results before and after the results of the drilling of the Moosehead-1 well. Also note that the modeling covers part of the block where the Graff-1 discovery occurred and suggests the area to be under the influence of a light oil/condensate to overmature oil window.
As stated by BPS President Marcio Rocha Mello in his paper presented at the African Week Oil Conference in Cape Town in 2011 and the Houston Conference and AAPG in 2016, the Namibian deep-water province is indeed a Land of Giants waiting to be awoken! Figure 8 has been presented by Dr. Mello since 2002 at several AAPG and African oil conferences, predicting how prolific the deep-water pre-salt Santos Basin in Brazil and the Cuanza (e.g., Angola) and Walvis & Orange basins (e.g., Namibia) in West Africa would prove to be, based on an original figure from Peter Szatmari in Mello and Katz, 2000 (AAPG Memoir 73). Peter was a genius geologist and considered one of the greatest in the history of Brazil. The plot was modified and presented at several AAPG events, as well as at Africa Oil Week, AAPG and the OTC Conference, among others.
The similarities between the Orange Basin and Santos Basin petroleum systems reflects the comparable source rock and depositional environments and, consequently, oil systems. Asymmetric rifting has, however, resulted in different sedimentary and subsidence histories that have, in turn, resulted in major differences in the distribution of reservoirs and light oil vs. gas and condensates, as well as in different reservoir types and depths along the margins. The syn-rift successions are, for example, deeper in the Brazilian marginal basins than in the West African margin (Mello et al., 1991). Consequently, when comparing the petroleum systems present around the South Atlantic Realm as possible exploration analogues, source rock presence and maturity must be considered. The results of the data from the drilling of the Wingat-1, Murombe-1 and Moosehead-1 wells in the offshore Walvis & Orange Basins provide strong evidence of the presence of at least two active petroleum systems in Namibia, with their respective hydrocarbon generation pods located deep offshore. The biomarker fingerprints of the migrated oils present in the sedimentary sections of several of the wells and the geochemical data of the Kudu 4 and Kudu 5 wells are just like those of the Santos, Campos and Cuanza basins (Fig. 3; Mello et al., 2011, 2012, 2014 and 2015).
In summary, the petroleum system concept, focusing on the nature and distribution of hydrocarbon fluids, places the Wingat-1, Murombe-1, Mosehead-1 (HRT) and Graff-1 (Shell) hydrocarbons into an interpretative framework that predicts it as the next “Land of Giants” in West Africa.
In summary, the petroleum system concept, focusing on the nature and distribution of hydrocarbon fluids, places the Wingat-1, Murombe-1, Moosehead-1 (HRT) and Graff-1 (Shell) hydrocarbons into an interpretative framework that predicts it as the next “Land of Giants” in West Africa.
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1991: Mello, M.R., Mohriak, W.U., Koutsoukos, E.A.M. & Figueira, J.C.A. Brazilian and West African oils: Generation, migration, accumulation, and correlation. Proceedings of the 13th World Petroleum Congress (Buenos Aires), 153-164.
2011: Mello, M.R., et.at., Correlation of the Petroleum systems from Santos and Namibian Offshore basins. OTC (Oil Technology Conference) Brazil
2012: Namibian Petroleum System: Land of Giants? Africa Week, Cape Town, South Africa
2012: Mello, M.R., Nilo Chagas de Azambuja Filho, Andre A. Bender, Silvana MariaBarbanti, Webster Mohriak, Priscila Scimitt, and Carlos Luciano, C, de Jesus: The Namibian and Brazilian southern South Atlantic petroleum systems: Are they comparable analogues? Geological Society, London Special Publications: Doi: 10.1144/SP369.18
2014: Mello, M.R., Operating in Africa is a return to our origins. Poster Publication African Week.
2015: Mello, M.R., Mohriak, W., Peres, W, ; Namibia: The last hunt for oil and gas continues in the land of giants. 34th Annual GCSSEPM Foundation Perkins-Rosen Research Conference, Houston, pp 919-963.
2016: Namibia: The hunt of Oil and Gas Continues in the land of giants. AAPG Conference, Houston.