Thursday, September 25, 2008

Ghawar's Magnificent Five

This article is from the Saudi Aramco Web site. It's in their news section, but they have one of those dynamical-type sites that don't let you link directly to articles. So I decided to "liberate" it:

DHAHRAN, September 22, 2008 -- Ghawar remains the world’s largest oil field 70 years after its discovery. Its size and continuity were not initially apparent, but a series of early exploration wells, now called the Magnificent Five, put the pieces of the puzzle together.

A 3D rendering of the Ghawar reservoir shows the Magnificent 5 discovery wells.

Amid the important commercial oil discoveries of Dammam (1938), Abu Hadriyah (1940) and Abqaiq (1940), geologists were exploring surface features to get a better picture of the potential of the Eastern Province.

While mapping the surface outcrops, geologists Ernie Berg and Max Steineke excitedly identified a broad, low-relief dome (called an anticline). Subsequent exploration established that this En Nala anticline at Haradh continued northward all the way to Ain Dar and Shedgum and was filled with oil.

King Saud ibn Abdulaziz inaugurates the gas injection facilities at Ain Dar in 1958.

Ghawar helped catapult Saudi Arabia into its role as the world’s leading oil producer. The super-giant field is 280 kilometers in length and consists of five contiguous oil fields from north to south: Ain Dar, Shedgum, ‘Uthmaniyah, Hawiyah and Haradh.

In 1995, a comprehensive 3D seismic campaign was conducted across the Ghawar field. The equipment used is a stark contrast to the early exploration team shown in the left photo.

Ain Dar No. 1

After World War II and with the resumption of drilling, the most obvious location to resume wildcat drilling was the Ain Dar structure because of its proximity to producing facilities at Abqaiq. Ain Dar No. 1 was drilled in 1948 and flowed oil to the surface during testing. It was put on production in early 1951 and is still producing today with the original well casings.

This well has been producing for more than 58 years with the aid of best-in-class reservoir management practices. It has produced 152 million barrels of oil and is still producing 2,100 barrels per day (bpd).

Haradh No. 1

In 1949, Aramco engineers initially wanted to drill a step-out well, Ain Dar No. 2, about 12 km to the south of Ain Dar 1. Instead, a second wildcat was drilled 185 km to the south at Haradh. At that time, no one openly suggested that the En Nala anticline would prove to be one continuous field 280 km long and up to 30 km wide. That possibility became very real when the Haradh No. 1 wildcat struck oil in 1949.

The Haradh well was nearly 200 km south of Ain Dar production facilities and, therefore, was not brought onstream until 15 years later. Haradh No. 1 was put in production in 1964 but shut down during the mid-1980s because of low demand. In 1990, after acid stimulation, it resumed production.

Today, 44 years after its first production, Haradh No.1 has produced more than 24 million barrels of oil and continues to produce at a rate of 2,300 bpd.

‘Uthmaniyah No. 1

‘Uthmaniyah No.1 was important in establishing that the En Nala anticline was oil-filled between Ain Dar and Haradh. This wildcat well was successfully drilled and tested in 1951. As with the other Ghawar wells, oil gravity was in the range of 33 degrees API (Arabian Light Crude).

‘Uthmaniyah No. 1 was brought onstream in 1956 and has since produced more than 20 million barrels of oil. Located on the eastern flank of ‘Uthmaniyah, close to the water, this well was the first of the discovery wells to employ water shutoff techniques to limit water production.

Shedgum No. 1

The Shedgum No. 1 discovery well was drilled in 1952 to delineate the En Nala anticline to the east of Ain Dar. The well struck oil in the Arab-D carbonate and was later brought onstream in 1954.

In 1968, the wellbore rock matrix was acidized to improve the flow of oil from the carbonate formation. In 1989, liners were run across the open hole to address future water encroachment.

Recently, the oil production rate was enhanced greatly for Shedgum No. 1 by recompleting the well with a horizontal sidetrack complemented with inflow control device (ICD) technology. Not only was the oil rate increased to more than 3,700 bpd, but the water cut has also been lowered significantly.

Shedgum No. 1 has produced more than 98 million barrels of oil over the past 55 years, and the application of new technologies will keep it producing for many years to come.

Hawiyah No. 1

The final discovery well of the magnificent five was Hawiyah No.1, which confirmed that Ghawar held oil between ‘Uthmaniyah and Haradh. Drilling was completed in 1953, and the well was put onstream in 1966, when the Hawiyah Field was developed.

The well received an acid stimulation treatment in 1977. With Saudi Aramco’s superior reservoir management practices, Hawiyah No. 1 has produced 51 million barrels of oil, and continues to produce today at 4,600 bpd.

Reservoir management

Since the discovery of the Ghawar field in 1948, Saudi Aramco has implemented best-in-class reservoir management practices and leading technologies that have evolved over the years. As a result, the Magnificent Five have demonstrated extraordinary performance with extended lifecycles and outstanding oil recovery.

One of the first reservoir management initiatives was gas reinjection in Ain Dar. In 1958, King Saud ibn Abdulaziz inaugurated the gas injection facilities in Ain Dar. The primary purpose of the program was to reinject produced gas to sustain reservoir pressure. Gas injection began in 1959 and continued for 20 years.

Water injection began in Ghawar in 1964 to provide additional pressure support — to maintain reservoir capacity to push oil to the surface. That technology, known as secondary recovery, provided a stepwise improvement in pressure support and began the displacement of oil from the outer edges of the Ghawar field toward the central regions to sustain oil production, as demonstrated by the phenomenal performance of the discovery wells.

In 1995, a comprehensive 3-D seismic campaign was conducted across the Ghawar field. The seismic profiles provided vital information on reservoir structure and distribution of fractures, guiding development and recompletions across Ghawar. That information, for example, was used to guide the placement of the horizontal well trajectory for Shedgum No. 1.

The Ghawar discovery wells, Ain Dar No. 1, Shedgum No. 1, Haradh No. 1 and Hawiyah No. 1 are still producing today with the original well casings. That speaks to the quality of workmanship and materials that went into the original wells.

Altogether, the Magnificent Five have produced nearly 350 million barrels of oil. There’s no telling how much more they will produce — as the end of their story is not yet in sight.

(Article by Darryl B. Fischbuch and Adeyinka X. Soremi)

No comments: