Finding Ghawar

Elephant Hid in Desert

The history of oil in the Middle East is essentially a story of giant oil fields (each containing over 500 million barrels).

Of the 932 known giants that researchers at the University of Texas in Austin have mapped, over 200 are located in the Persian Gulf region, which accounts for about 2 percent of Earth’s land area – and the “Elephant of All Elephants” (AAPG EXPLORER, January 2005) is Saudi Arabia’s Ghawar field.

Discovered in 1948, Ghawar started to produce oil in 1951 – 60 years ago – but to this day it remains the world’s richest and most productive oil field.


Today the oil industry in Saudi Arabia is in full control of a state-run company, Saudi Aramco. The company’s origin, however – as well as the history of oil discovery in the kingdom – dates back to the Arabian American Oil Company (Aramco).

The first oil field discovered in Saudi Arabia was not Ghawar but Dammam, in March 1938, followed by Abu Hadriyah (March 1940) and Abqaiq (December 1940). These fields are located in the Eastern Al Hasa region where pioneering mapping began by American geologists in the early 1930s.

Max Steineke
Max Steineke

The legendary Max Steineke and Tom Kock, both AAPG members with California Arabian Standard Oil Co. (Socal) in 1935 first spotted topographic indications of the En Nala anticline on which Ghawar sits.

In 1940, Ernie Berg, a young Aramco geologist who was mapping areas near the Abqaiq field, noted that the Wadi Sahaba, a seasonal river valley in the Haradh area, took a sudden bend from its east-west direction toward the south.

Berg related this wadi diversion to a north-south trending subsurface anticline. Steineke, his boss, supported the idea.

Shallow structural-stratigraphic drillings in the desert (a technique Steineke had developed to map the subsurface geology and collect pre-Neogene information) confirmed the existence of what came to be called the En Nala (“the Slippers”) anticline.


After World War II, exploration resumed on the Arabian Peninsula, and the information from shallow drillings were supplemented with gravity and magnetic surveys. The En Nala anticline was thus better imaged.

This“whale back” structure, about 280 kilometers long and 30 kilometers wide on average, contains six major structural culminations; from north to south, they are Fazran, Ain Dar, Shedgum, Uthmaniyah, Haradh and Hawiyah.

In 1948 Aramco drilled a test well at Ain Dar, which hit oil in June, marking the first post-war discovery in the kingdom. In a letter dated July 6, 1948, S.V. Campbell, an Aramco manager, reported the good news to the Saudi finance minister Shaikh Abdullah Sulaiman:

“In a 20-minute test at 6,685 to 6,746 feet, gas in the Ain Dar well rose to the surface in six minutes and oil rose to the surface in 11 minutes.”

More wildcats on the anticline, Haradh No. 1 (February 1949), Uthmaniyah No. 1 (April 1951), Shedgum No. 1 (August 1952) and Hawiyah No. 1 (1953) all discovered light crude (32-36° API) from the Upper Jurassic carbonate reservoir (the 100-meter Arab-D member) at depths of 2,000-2,330 meters.

By 1953, the geologists recognized that all these prospects were actually parts of a single field; they named it Ghawar, after the wide pastoral landscape that local Bedouins called Al Ghawar.

The northernmost part of the supergiant, Fazran, was discovered in 1957. By then 129 wells were producing 0.6 million barrels of oil per day. Except for Uthmaniyah No. 1, all the other discovery wells at Ghawar still produce oil.

The first detailed report about Ghawar by the Aramco geologists was presented at the AAPG convention in Los Angeles in March 1958 and published in AAPG BULLETIN in February 1959 – a report that, amazingly, remains the cornerstone of our knowledge of this field.


In the 1970s, deeper drillings in the Ghawar field discovered enormous volumes of natural gas from the Permian carbonates of the Khuf Formation.

Public knowledge about the world’s largest field ironically remains scanty. This has led to speculative debates about Ghawar’s peak production and near-future demise – for example, Matthew Simmon’s 2006 book Twilight in the Desert.

AAPG member Abdul Kader M. Al-Afifi, a senior geologist with Saudi Aramco, reported in his 2004 AAPG Distinguished Lecture that Ghawar produced 4.6-5.2 MMbopd from 1993 through 2003.

The Ghawar anticline is draped over a basement horst, which started to develop during the Late Carboniferous extensional uplift in the region, which, in turn, eroded the middle Paleozoic sediments at Ghawar. Bounding normal faults have throws as much as 3,000 feet at the Silurian level, but they die out in the Triassic section, according to Afifi, who is past president of the AAPG Middle East Region (AAPG EXPLORER, January 2005).

The Cenozoic anticline at Ghawar, called the En Nala structure, is asymmetrical with a steeper western flank, and a minor component of right lateral strike slip.

The oil at Ghawar was sourced from Jurassic organic-rich marlstone.

The producing oil reservoir is the late Jurassic Arab-D limestone, which is about 280 feet thick and occurs 6,000-7,000 feet beneath the surface. Afifi also noted that reactivation of the structure during Arab-D deposition localized grain-dominated shoals in the north, upgrading the quality of the reservoir, which improves upward as it progresses from lime mudstone to skeletal oolitic grainstone.

Fracture density increases going deeper in the section, enhancing permeability in the finer-grained mudstones and carbonates.

Overall, 50-60 percent of Saudi oil production has historically come from Ghawar. The field’s highest production was 5.7 MMbopd in 1981. Water cut (ratio of water to total liquid production) in the field was about 35 percent in 2003. Gas production was about eight billion cubic feet per day, out of which two billion was associated gas and six billion non-associated gas.

The International Energy Agency has placed Ghawar’s ultimate oil reserves at 140 billion barrels, including 66 billion barrels already produced and 74 billion barrels remaining oil.

How accurate these estimates are remains to be seen – but to put these figures in context, consider that the proven U.S. oil reserves currently stand at about 22.3 billion barrels.

It is apt to end this essay with a note on Steineke, a Stanford graduate and Aramco’s chief geologist, who contributed so much for the early oil discoveries in Saudi Arabia. He died in 1952, one year after Ghawar came onstream.

Comments (0)

 

Historical Highlights

Historical Highlights - Rasoul Sorkhabi

Rasoul Sorkhabi is a research professor at the University of Utah’s Energy and Geoscience Institute and is co-author of “Geological Excursions Around Miri, Sarawak” (Ecomedia, Malaysia, 2010). This paper was presented in the History of Petroleum Geology session at AAPG’s annual convention in New Orleans in 2010

Historical Highlights

Historical Highlights - Hans Krause

Hans Krause is an AAPG Honorary Member, Distinguished Service Award winner and former chair of the AAPG History of Petroleum Geology Committee.

Historical Highlights

A History-Based Series, Historical Highlights is an ongoing EXPLORER series that celebrates the "eureka" moments of petroleum geology, the rise of key concepts, the discoveries that made a difference, the perseverance and ingenuity of our colleagues – and/or their luck! – through stories that emphasize the anecdotes, the good yarns and the human interest side of our E&P profession. If you have such a story – and who doesn't? – and you'd like to share it with your fellow AAPG members, contact the editor.

View column archives

Image Gallery

See Also: Book

Desktop /Portals/0/images/_site/AAPG-newlogo-vertical-morepadding.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 4232 Book

See Also: Bulletin Article

Sequence stratigraphy and coal cycles based on accommodation trends were investigated in the coal-bearing Lower Cretaceous Mannville Group in the Lloydminster heavy oil field, eastern Alberta. The study area is in a low accommodation setting on the cratonic margin of the Western Canada sedimentary basin. Geophysical log correlation of coal seams, shoreface facies, and the identification of incised valleys has produced a sequence-stratigraphic framework for petrographic data from 3 cored and 115 geophysical-logged wells. Maceral analysis, telovitrinite reflectance, and fluorescence measurements were taken from a total of 206 samples. Three terrestrial depositional environments were interpreted from the petrographic data: ombrotrophic mire coal, limnotelmatic mire coal, and carbonaceous shale horizons. Accommodation-based coal (wetting- and drying-upward) cycles represent trends in depositional environment shifts, and these cycles were used to investigate the development and preservation of the coal seams across the study area.

The low-accommodation strata are characterized by a high-frequency occurrence of significant surfaces, coal seam splitting, paleosol, and incised-valley development. Three sequence boundary unconformities are identified in only 20 m (66 ft) of strata. Coal cycle correlations illustrate that each coal seam in this study area was not produced by a single peat-accumulation episode but as an amalgamation of a series of depositional events. Complex relations between the Cummings and Lloydminster coal seams are caused by the lateral fragmentation of strata resulting from the removal of sediment by subaerial erosion or periods of nondeposition. Syndepositional faulting of the underlying basement rock changed local accommodation space and increased the complexity of the coal cycle development.

This study represents a low-accommodation example from a spectrum of stratigraphic studies that have been used to establish a terrestrial sequence-stratigraphic model. The frequency of changes in coal seam quality is an important control on methane distribution within coalbed methane reservoirs and resource calculations in coal mining. A depositional model based on the coal cycle correlations, as shown by this study, can provide coal quality prediction for coalbed methane exploration, reservoir completions, and coal mining.

Desktop /Portals/0/PackFlashItemImages/WebReady/accommodation-based-coal-cycles-and-significant.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 5686 Bulletin Article

See Also: DL Abstract

The enhanced production of unconventional hydrocarbons, the mitigation of biosourcing, and the advancement of carbon capture and storage, now combine to create significant financial and technical challenges to the global oil and gas industry.  Emerging and especially promising Geobiology approaches to these issues include utilization of the physical and biogeochemical activity of microorganisms that inhabit deeply buried hydrocarbon reservoirs.

Desktop /Portals/0/images/_site/AAPG-newlogo-vertical-morepadding.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 11396 DL Abstract

See Also: Field Seminar

This field seminar offers an excellent opportunity for the students to walk on a variety of modern terrigenous clastic depositional systems while observing sedimentary processes, modern sedimentary structures, and numerous trenches illuminating the three-dimensional architecture of each area.

Desktop /Portals/0/PackFlashItemImages/WebReady/fs-Modern-Terrigenous-Clastic-Depositional-Systems.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 2575 Field Seminar

See Also: Short Course

This course will address integration of source rock, produced oil and gas, and mud gas data to better understand and exploit 3-dimensional details of petroleum systems. Carbon isotope and oil biomarker geochemistry will be stressed as a way to determine quantity and type of generated hydrocarbons and migration distance and direction within source rock and tight oil plays.

Desktop /Portals/0/PackFlashItemImages/WebReady/Practical-Aspects-Of-Petroleum-Geochemistry-For-Resource-Plays-hero.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 13514 Short Course