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Geological Features and Distribution Patterns of Giant Fields Discovered in the New Century

Abstract

This study attempts to document the geological features, distribution patterns, and discovery trends of 120 giants (recoverable reserves of 500 MMboe or greater) discovered in the period of 2000–2012. At the same time, we discuss how future exploration will identify additional giant fields along several trends related to basin types, stratigraphic intervals, reservoir and trap types, and other indicators. Giant fields discovered in the new century are concentrated in seven dominant clusters: Middle East (28), offshore Brazil (19), offshore East Africa (13), Central Asia (9), Northwest Shelf of Australia (8), offshore West Africa (6), and Gulf of Mexico (5). The top six basins with the largest share of total giant proved plus probable petroleum reserves are the Amu-Darya (accounting for 27.0%), Santos (13.2%), Arabian (9.8%), North Caspian (7.6%), Zagros (6.9%), and Tanzania (6.8%) basins. Marine carbonate reservoirs host 54.5% of the total; they are followed by turbidites (17.6%), clastics (15.9%), and lacustrine carbonates (12.0%). The combination trap is the dominant trap type and entraps 64.6% of the total. Passive margin basins host 74 giants and account for 43.4% of the total giant reserves. They are followed by rift basins with 13 giants and 39.9% of the total and foreland basins with 28 giants and 12.9% of the total. Stratigraphically, the reserves are concentrated in two intervals: the Jurassic and the Cretaceous, which host 35.4% and 22.7% of the total, respectively. In terms of physical environment, 50.1% of the giant 2P reserves are distributed in 40 onshore giants, 25.7% in 53 deepwater fields, 16.3% in 17 shallow-water giants, and 7.9% in 10 ultradeepwater giants. Compared with giants discovered in previous decades, the giants of the new century show five discovery trends. Firstly, giant fields are continuously found in areas with previously discovered giants. The Tanzania, Santos, Levantine, and Krishna basins where no giants had ever been discovered prior to 2000, have emerged as the major frontiers with three or more giant discoveries. Secondly, deep and ultradeep water has been increasing in importance as the domain for discovering new giants. Thirdly, more gas giants and more gas reserves have been found in the new century. Fourthly, stratigraphic traps entrap an increasing proportion of the total reserves in giant fields. Finally, more giants and more reserves are discovered in deep reservoirs with a burial depth of 15,000 ft or more.