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Introduction (Figures 1 and 2)The two sessions comprising the symposium, entitled Giant Oil and Gas Fields of the Decade 1990-2000, represent the fourth of a four-decade series, each commemorating important giant discoveries, and resulting in the publication of AAPG memoirs, rich in their geologic detail. Presentations at the Denver 2001 symposium represent case histories of giant fields in 14 countries:
We are most grateful for the authors and their respective companies for their contributions to the success of this important series. As you probably know, I have been privileged to be associated with this series during its more than forty-year span, and I have been very proud of all those who have been played a part in its longevity and accomplishments.
Scope and Definitions (Figures 3 and 4) In our study we use the definitions that a giant oil field contains more than 500 million barrels of oil recoverable, and a giant gas field contains more than 3 trillion cubic feet of gas (Figure 3). During the 1990’s 37 giant oil fields were discovered, and 40 giant gas fields were also discovered (Figure 4). Let us now review these discoveries in the context of their global location. Middle East –Asian Giant Oil Fields (Figure 5)This region contains the largest oil field found in the 1990’s: Azadegan, with 6 billion barrels of oil. The field is located in southwestern Iran, near Iraq. Last November, Iran and Japan reached an agreement allowing Tokyo priority bidding rights to develop the field, a key goal for oil-dependent Japan. The Saudi 1990’s giants include Hazmiyah and Raghib, examples of Paleozoic exploration success in central Arabia. The Chinese giant field is Peng Lai (Patton et al., 2001). African Giant Oil Fields (Figure 6)During the 1990’s African giant oil fields were discovered in Angola, Nigeria, Algeria, Libya, and Equatorial Guinea. Case history of Kizomba Field, offshore Angola, is given by Reechmann et al. (2001); Nigerian fields are characterized by Eyer and Saugy (2001). Africa contains the fifth largest oil field discovered in the 1990’s: Ourhoud in Algeria (Lunn et al., 2001). Production is from Triassic reservoirs at approximately 3000 meters. European Giant Oil Fields (Figure 7)Only one country was represented by discoveries of giant fields in the 1990’s: Norway, with three giant offshore fields--Grane, Norn, and Skarv-Idun. Grane, the most southern of the three, is the largest with 700 million barrels recoverable. Production is from Paleocene submarine fan systems.North American Giant Oil Fields (Figure 8) The deepwater fields, Crazy Horse and Mad Dog, represent the United States’ giant discoveries. Crazy Horse was the fourth largest oil field found in the 1990’s. Lawrence (2001) describes exploration and development in this area. Mexican 1990 giant discoveries are Zaap and Sihil (Aquino et al., 2001). Rosillo et al. (2001) characterizes the Jujo-Taecominoacan Field, and Cabrera-Cuervo (2001) also describes offshore Litoral de Tabasco fields. South American Giant Oil Fields (Figure 9) During the 1990’s two giant oil fields were discovered in onshore Colombia (Cusiana [Warren et al., 2001] and Cupiagua); and three giants discovered offshore Brazil are Roncador (Guimaraes et al., 2001), Albacora East, and 1-RJS-539. Two of the five largest global oil discoveries in the 1990’s occurred in South America: Roncador (2nd largest) and Cusiana (3rd largest). Southeast Asia – Australian Giant Oil Field (Figure 10)Only one giant oil field was discovered in the 1990’s in the SE Asia – Australian region: West Seno in Indonesia. This is in sharp contrast to the several gas discoveries in the region, as is noted below.
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Figure 1—AAPG’s symposia of giant oil and gas fields: a four-decade
series.
Figure 3—Definitions of giant oil and gas fields.
Figure 4—1990’s discoveries of giant oil vs. gas fields.
Figure 6—1990’s giant oil fields, Africa.
Figure 7—1990’s giant oil fields, Europe.
Figure 8—1990’s giant oil fields, North America. 
Figure 9—1990’s giant oil fields, South America.
Figure 10—1990’s giant oil field, Southeast Asia – Australia.
Figure 11—1990’s giant gas fields, Middle East – Asia.
Figure 12—1990’s giant gas fields, Africa.
Figure 13—1990’s giant gas fields, Europe.
Figure 14—1990’s giant gas fields, South America.
Figure 15—1990’s giant gas fields, Southeast Asia – Australia.
Figure 16—Giant field trends: 1990’s deepwater discoveries.
Figure 17—Giant field trends: gas discoveries, total discoveries, and
stratigraphic emplacement.