Print this pageGiant Oil and Gas Fields of the Decade 1990-2000: An Introduction*
M.T. Halbouty
Michel T. Halbouty Energy Company, Houston, TX.
Search and Discovery Article #20005 (2001)
*Online version of presentation at Symposium, Giant Oil and Gas Fields of the Decade 1990-2000, AAPG Convention, Denver, CO, June 5, 2001. Appreciation is expressed to Mr. Halbouty for permission to publish this version and to M.K. Horn for providing the material in digital formats.
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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.
Middle East – Asia Giant Gas Fields (Figure 11) There were 14 giant gas fields discovered in the Middle East and Asia during 1990’s, including four of the five largest discoveries of all regions, three of which are in Iran, the other being in Azerbaijan. The largest, South Pars field of Iran, “discovered” in 1991, is the across-border extension of the supergiant North Field of Qatar, discovered in 1971. African Giant Gas Fields (Figure 12) There were 3 giant gas fields discovered in Africa during the 1990’s, two of which are located offshore Nile Delta, Africa. The third giant gas field is located in western Libya. European Giant Gas Fields (Figure 13) There were three European giant fields discovered in the 1990’s, all located in the Voring and More Norwegian frontier basins. The largest gas field -- the deepwater Ormen Lange -- is the result of post-break-up compression, which has formed some of the most attractive structural traps in this Norwegian frontier area. South American Giant Gas Fields (Figure 14) The six South American giants appear to lie in an arc described by the deeper portions of the foredeep basins that run north-south against the South American Cordillera. The largest gas field discovery, Itau-San Alberto, is in Bolivia. With 14 tcf, it ranks as the fifth largest gas discovery of the 1990’s. Southeast Asia – Australian Giant Gas Fields (Figure 15) There were thirteen giant gas fields discovered in the 1990’s, spread out over this large area. All are offshore, with the exception of Sumpal, which is in onshore South Sumatra. The largest discovered field in the region is Tangguh-Vorwata with 11 tcf, in the Bintuni basin (located in the westernmost part of Irian Jaya, Indonesia). Our Indonesian case history is Peciko (Lambert et al., 2001), which produces gas from Upper Miocene deltaic reservoirs. It is located in the prolific Kutei basin. Deepwater Discoveries (Figure 16) Due to advancing technology, there was and is a clear shift toward the search and discovery below the deep waters surrounding the global continents. During the 1990’s, giant deepwater discoveries were made in offshore Brazil, Angola, United States, Indonesia, Australia, Norway, Philippines, and Russia. More Giants, Greater Percentage of Giant Gas Fields (Figures 17 and 18) Over the 30-year course of our study of giant fields, and as documented in the associated AAPG memoirs, we have seem some remarkable changes, two of which are: 1. There has been a 53% increase in the number of giant fields during the 30-year time period. 2. Within this inventory of fields, gas discoveries are increasing at an accelerated rate when compared to oil discoveries. This trend continued in the year 2000, when 8 giants were discovered, seven of which were gas. The lone oil discovery was the supergiant East Kashagan found in the Caspian Sea. Stratigraphic-controlled giant fields (Figures 17 and 18) Our final giant field trend is the increase of stratigraphic-controlled traps as a percentage of all traps. The data used for this comparison are our original giant field tables published in 1968 in Memoir 14, compared with present-day data provided by the IHS Group. Historically, many stratigraphic traps were found accidentally while drilling for a structural objective. As pointed out by Dolson et al. (1999) in the AAPG Treatise of Petroleum Geology, this was due to (1) an historical emphasis on structures and (2) the difficulty in seismically imaging stratigraphic-trap components. Hence 30 years ago only about 10% of the giants were stratigraphically controlled. However, seismic imaging of stratigraphic-trap components has become a reality. This has led to a major increase of giant field discoveries with a strong stratigraphic component. Ninety-three of the 427 giants fields on our 2000 list contain strong stratigraphic components. We believe this trend will continue into the future, tracking the on-going improvements in seismic technology. Summary and Conclusions (Figure 19) Deepwater areas are increasingly important settings for giant fields. Discoveries of gas fields are increasing with respect to giant oil fields. Seismic imaging has been critical to discovery of giants and will continue in that role. A major result has been an increase in stratigraphic emplacement, and that trend also will continue. I would like to acknowledge Jerry Eyer, my co-chairman of the first session of the symposium, and Bob Merrill and Mike Horn, chairmen for the second session; also, Henry Pettinghill is acknowledged for his input in constructing the giant field summaries used in this study. (Clicking on a reference will open it in PDF format) Dolson, J.C., M.S. Bahorich, R.C. Tobin, E.A. Beaumont, L.J. Terlikoski, and M.L. Hendricks, 1999, Exploring for stratigraphic traps, in Exploring for oil and gas traps: AAPG Treatise of Petroleum Geology / Handbook of Petroleum Geology, p. 21-1 – 21-68. |
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.
Figure 18—Giant field inventory—30-year comparison (1970-2000)—oil
vs. gas giants and structural vs. stratigraphic.
Figure 19—Summary: factors related to 1990’s giant fields.