Giant Oil and Gas Fields of the 2000s: A New Century Ushers in Deeper Water, Unconventionals, and More Gas

Abstract

Estimated recoverable oil and gas from giant field discoveries from 2000 through 2009 was 383 billion barrels of oil equivalent (BBOE)—a 92% increase from the prior decade and the largest addition from giant fields since the 1970s. This dramatic increase in giant field resources was driven by the emergence of shale gas and tight oil discoveries in North America. These so-called unconventional or continuous resource plays added almost 177 BBOE of new resources—mostly from super-giant plays like the Marcellus, Bakken-Three Forks, Eagle Ford, and Montney formations. In harmony with recent trends, giant natural gas discovery volumes greatly exceeded those of oil and contributed about 260 BBOE (1558 trillion cubic feet) of new resources. Traditional conventional giant discoveries added 198 BBOE of new resource—slightly less than in the prior decade and almost 55% of the total. Super-giant fields such as Galyknysh (Yoloten) with 67 BBOE gas and condensate in Turkmenistan, Kashagan in Kazakhstan; Lula in Brazil; and Kish 2 in Iran accounted for almost 60% of the giant conventional resources. The share of deepwater discoveries increased and contributed 23% of the conventional giant field volumes. The Santos Basin mega presalt and the Levantine Basin were the most important deepwater play openers.

Geochemical Characteristics and Distribution of the Subsalt Source Rocks in the Santos Basin, Brazil

“…Correspondingly, three sets of giant thick sedimentary sequences were developed, namely the continental giant sequences of the Guaratiba Group in the rift period, the evaporative salt giant sequences of the Ariri Formation in the transition period, and the marine giant sequences of the passive continental margin carbonates, deepsea mudstones, and deep-sea turbidite sandstones in the drift period (Figure 2). 16,27,28 From the bottom to the top, the basin mainly develops four sets of reservoirs: the lacustrine limestone of the Cretaceous Guaratiba Group, the shallow-sea sandstone, carbonate of the Florianopolis Group, the turbidite sandstones of Santos Group, and the turbidite sandstones of the Paleogene−Neogene Marambala Group. [13][14][15]27 Oil and gas are mainly enriched in the limestone reservoir of the subsalt Guaratiba Group.…”

“…Correspondingly, three sets of giant thick sedimentary sequences were developed, namely the continental giant sequences of the Guaratiba Group in the rift period, the evaporative salt giant sequences of the Ariri Formation in the transition period, and the marine giant sequences of the passive continental margin carbonates, deep-sea mudstones, and deep-sea turbidite sandstones in the drift period (Figure ). ,, From the bottom to the top, the basin mainly develops four sets of reservoirs: the lacustrine limestone of the Cretaceous Guaratiba Group, the shallow-sea sandstone, carbonate of the Florianopolis Group, the turbidite sandstones of Santos Group, and the turbidite sandstones of the Paleogene–Neogene Marambala Group. − , Oil and gas are mainly enriched in the limestone reservoir of the subsalt Guaratiba Group. Two sets of source rocks are mainly developed in the basin, one is the lacustrine source rocks of the Lower Cretaceous Barremian–Aptian Stage Guaratiba Group in the subsalt rift period, and the other is the marine source rocks of the Upper Cretaceous Cenomanian–Turonian Stage Itajai-Acu Formation in the postsalt drift period. ,, In recent years, the discoveries of a large amount of oil and gas have confirmed that the lacustrine mudstones of the Guaratiba Group deposited in the subsalt rift period are the main source rock of the basin. ,,, The lacustrine source rocks of the Guaratiba Group consist of the Picarras Formation and the Itapema Formation source rocks.…”

“…13 Since 2006, several giant oil and gas fields such as Lula, Jupiter, Sapinhoa, Franco, and Libra have been continuously discovered in the field of lacustrine carbonates of the subsalt strata in the deep-water area of the Santos Basin, revealing that the subsalt strata of the basin have rich oil and gas resources and great exploration potential. 14 − 16 …”

“…By the end of 2016, 38 oil and gas fields have been discovered in the subsalt strata of the basin, with a total proved recoverable reserves of about 30 billion barrels, accounting for 94% of the Santos Basin . Since 2006, several giant oil and gas fields such as Lula, Jupiter, Sapinhoa, Franco, and Libra have been continuously discovered in the field of lacustrine carbonates of the subsalt strata in the deep-water area of the Santos Basin, revealing that the subsalt strata of the basin have rich oil and gas resources and great exploration potential. − …”