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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 due 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.
H. Court Young
Geologist, author and publisher
Promoting awareness through the written word
http://www.hcourtyoung.com
http://www.tmcco.com
(303) 726 8320
©March, 2008 |
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