According to an article in World Oil Magazine entitled, Three super-giant fields discovered offshore Brazil, by Arthur Berman; three new offshore oil fields have been discovered in Brazil's Santos Basin. The Brazilian oil company, Petrobas, announced, these fields, named Tupi, Jupiter and Carioca located 174 miles east of the State of Sao Paulo in the Atlantic Ocean.



Based on preliminary drilling, these new wells may redefine the Carioca geologic structure, in the Santos Basin. This area may cover an area of 1,000 square miles.

How does this new oil discovery compare with the largest oil field in the world, Ghawar in Saudi Arabia? Ghawar was discovered in 1951. It has produced an estimated 55 billion barrels of oil, averaging 5 million barrels per day.

Ghawar covers an area of about 2,000 square miles. It averages 31 miles wide by 174 miles long. It is located in the eastern part of Saudi Arabia, about 75 miles west of the Gulf of Bahrain. It has produced an estimated 55 to 65 percent of the total Saudi production.

Oil production from Ghawar comes from Jurassic age carbonate rocks. The average well depth is 6 to 7 thousand feet, with an oil thickness of 250 feet. This field has an inert anhydrous (calcium sulfate) seal.

The American Petroleum Institute (API) defines oil by its density. Light oil has a density of 38 to 34 API. Medium oil has a density of 32 API, and heavy oil has a density of 29 API or less. The light oils are the most energy efficient and the easiest to refine. The heaver the oil the more like tar it is. West Texas light sweet crude has been a standard by which oils have been compared for many years.

Preliminary results from Brazil's Santos Basin fields give a density ranging from 27API in the Carioca field to 30 API in the Tupi field. As you can see, this oil is significantly heaver than that of the Ghawar oil.

The oil bearing formations are Lower Cretaceous, almost 100 million years younger than the oil bearing strata of the Saudi fields.

In addition, the Santos Basin is entirely offshore. These wells will be drilled in 7,000 feet of water. They have an average total depth of over 22,000 feet. The oil thickness is estimated at 250 to 394 feet.

There are several major production challenges in the Santos Basin. One is the drilling in such deep water. Another problem is the extent and type of cap rock covering the oil layer. In Ghawar, the cap rock was a relatively inert anhydrite. However, in the Santos Basin the cap rock is corrosive salt. Drilling and maintaining casing in 6,500 feet of this salt layer is a significant technical challenge.

These three areas of the Santos Basin are estimated to contain almost 40 billion barrels of oil. If these estimates are true, then these fields will be the third largest ever discovered, and the largest discovered in the last 30 years. However, this oil is much harder to get out, is much higher density and therefore harder to refine.

While this discovery is good, it tends to give credibility that the days of cheap oil have passed. These new oil fields comprise a 40 billion barrel downturn when compared to the super giant fields of the past. The world needs to take notice and become much more aware of how we develop and use this increasingly hard to get resource.

Two sources must be credited for the technical and factual information in this article. These sources are Twilight in the Desert by Matthew R. Simmons and the article in World Oil Magazine noted at the beginning. I wanted to give you a quick and incisive overview of these important developments in the oil industry.