When one examines Saudi Arabia’s historical dominance over other oil-producing countries, it all comes down to one field—Ghawar. This massive structure is so productive that it typically gets compared to other countries, not other fields. In fact, according to the Energy Information Administration (EIA), the field has more oil reserves than all but seven countries.

The sheer size of the field—257 km (160 miles) long and 26 km (16 miles) wide by some estimates—makes it comparable to some of the large shale plays in North America. But this is a conventional oil field that, at its peak, produced 6.5 MMbbl/d, according to the EIA. Current production is still 5 MMbbl/d and 71 MMcm/d (2.5 Bcf/d), according to “Hydrocarbons Technology.”

That site also noted that Ghawar accounts for an estimated 6% of the world’s total daily crude output.

Humble beginnings

One must scare up some pretty distant history to harken back to a time when Saudi Arabia was not the dominant oil-producing giant that it is today. An article in the AAPG “Explorer” titled “Elephant hid in desert” did a pretty good job. The Arabian American Oil Co. (Aramco) began a series of discoveries in the 1930s and early ’40s in the Eastern Al Hasa region. American geologists had begun mapping the region in the early ’30s.

Geologists from California Arabian Standard Oil Co. (Socal), meanwhile, became interested in the topography near the En Nala anticline in 1935. Following their lead, Aramco geologists began examining the area, noting that the Wadi Sahaba, a seasonal river, took a sudden bend to the south. Shallow drilling confirmed the existence of the anticline.

World War II intervened, but afterward explorers returned to the region, acquiring gravity and magnetic surveys to better image the anticline. They determined that the anticline contained six major structural culminations. Aramco drilled a test well in 1948 and made the first post-war discovery in the Kingdom. The well, tested from 2,038 m to 2,056 m (6,685 ft to 6,746 ft), produced gas within six minutes and oil within 11 minutes, with initial production of 15,600 bbl/d.

More wildcats would follow: Haradh No. 1 in February 1949, Uthmaniyah No. 1 in April 1951, Shedgum No. 1 in August 1952 and Hawiyah No. 1 in 1953. All discovered light crude from Upper Jurassic carbonates, now known as the Arab-D member.

By the time of the final discovery, it was becoming clear that all of these discoveries were part of the same enormous field. It was named Ghawar based on the name the Bedouin tribes used for the region.

By 1957, when the northernmost discovery was made, there were 129 wells producing 600,000 bbl/d. All but one of the original discovery wells were still producing oil as of 2011, when this AAPG article was published.

“The first detailed report about Ghawar by the Aramco geologists was presented at the [American Association of Petroleum Geologists] 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,” the authors noted.

More recent deeper drilling has uncovered vast natural gas reserves in the Permian carbonates, and the development of the southern Hawiyah and Haradh areas during the mid-1990s has improved oil production rates, according to “Hydrocarbons Technology.”

The Late Carboniferous extensional uplift caused a basement horst to develop, and it is over this horst that the Ghawar anticline is draped. The asymmetrical En Nala structure has a steep western flank and “a minor component of right lateral strike-slip,” the authors noted. Oil is sourced from Jurassic marlstone.

The Arab-D member is about 85 m (280 ft) thick and improves in quality in the shallower sections.

Ghawar today

The Ghawar Field is located in the eastern portion of the Empty Quarter of the Arabian peninsula about 100 km (60 miles) southwest of Dhahran in the Al Hasa province in Saudi Arabia. It is operated by Saudi Aramco.

The field has long undergone secondary recovery methods. Gas injection was introduced in 1958, according to “Hydrocarbons Technology,” and water injection began in 1964 to provide pressure support. Today water is pumped by pipeline from the Qurayyah Seawater Treatment Plant.

In 1995 Aramco conducted a 3-D seismic survey to examine the reservoir structure and fracture distribution to guide future development of the field. More recently the company began the Haradh III project, which relies on maximum-reservoir-contact wells and downhole interval control valves for flow control. Geosteering also has been used, and wells have been equipped with intelligent sensors for continuous monitoring.

The site noted that Ghawar had more than 3,000 injector and oil producer wells by the end of 2012. Halliburton is the prime contractor and was awarded a five-year contract in 2009 to develop as many as 185 oil production, water injection and evaluation wells. Aramco also is working on a carbon capture and storage (CCS) strategy at Ghawar to combine CCS with EOR. The project, expected to be completed at the end of 2014, would require 1.1 MMcm/d (40 MMcf/d) to be pumped from the Hawiyah and Uthmaniyah gas processing plants. It also would require an 800,000 ton/year CCS facility and a 70-km (43-mile) pipeline to transport CO2 to the site.

Finally, the company is planning to award FEED contracts to develop three shale gas fields, one of which resides in the southern part of the Ghawar Field.

An aging giant?

Ghawar has been the world’s largest oil field for decades, a distinction that brings with it the ability to control, to some extent, the world’s supply of oil. But its dominance is waning as countries like the U.S. exploit their shale oil resources. And many question its ability to keep up the good work for much longer.

In an article on the “Energy and Capital” website posted in February of 2013, author Justin Williams discussed the debate on Ghawar’s future. “Some experts believe [that] Ghawar has reached its peak and is in decline,” Williams wrote. “Saudi Arabia will dispute that position every step of the way and assure the public that Ghawar will continue to produce at current levels for years to come. The nation claims the field most likely has 50 Bbbl left to extract.”

Many sources noted the difficulty of getting reliable data, or in fact any data, from Saudi Aramco statements.

While the field may play less of a role in world politics and economies in the future its stature as a game changer can’t be denied.