Crude oil or Petroleum is a complex mixture of hydrocarbons of various compositions along with other organic compounds found in the different rock formations in the Earth. The flammability and its natural existence are the main properties that contribute to its importance. The crude oil production, over the years has varied for different countries but in the recent past Saudi Arabia has been the leading oil producer in the world with its reserves estimated to be around 267 billion barrels.
In the mid of 2008, the total production of oil from Saudi Arabia was estimated to be around 11 million barrels per day and now they have plans to increase it to around 12. 5 million barrels per day (US_Energy_Intelligence_Administration, 2008). Over 90% of the total oil production from Saudi Arabia is dominated my five large fields and nearly 60% of it comes from Ghawar Field (IAGS, 2004) as it has a production of nearly 5 million barrels per day. Ghawar Field The Ghawar field is the largest oil field in the world with a daily production of nearly 5.
5% of the world’s total oil produced per day (Morton, 2004). It stretches 174 miles in length and 16 miles across to cover 1. 3 million acres. This enormous area is divided into six regions from the north to south namely Fazran, Ain Dar, Shedgum, Uthmaniyah, Haradh and Hawiyah. The Arab-D reservoir accounts for almost all of the reserves and production. This field was discovered in 1948 and the production started in 1951. It reached its peak in 1981 with a production of 5. 7 million barrels per day (Al-Anazi, 2007).
In the mid eighties, the production from Samotlor Field in Russia started dominating the world market but with the development of southern Haradh and Hawiyah fields in 1996, the Ghawar Field again reached the peak of 5 billion barrels per day. Figure taken from a article from Abdulkader M. Afifi, Saudi Aramco, Dhahran, Saudi Arabia (Afifi, 2005). The Ghawar fields is entirely owned and driven by Saudi Aramco, which is the national oil company of Saudi Arabia. It is also the largest oil corporation in the world. Geology The Arab-D reservoir is the main oil producing reservoir in the Ghawar field.
Mainly constituting of limestone with some traces dolomite, it is stratigraphically the D member of the Arab Formation and also the upper part of Jubalia Formation. These formations are believed to be Upper Jurassic, Kimmeridgian in age based on the ammonite and benthonic foraminiferal evidences (Robert F. Lindsay). The Figure shows the contour for the Top Arab-D depth Structure. The Jurassic Arab-D reservoirs have a thickness of above 200feets which occurs at a depth of around 6000 to 7000feets. The average porosity in this region is nearly 15% (Robert F. Lindsay) but at some places the porosity goes as high as 30%.
It has an abundance of interparticle porosity along with some moldic porosity. The microporosity is common in both the dolomite as well as limestone lithologies. It is believed that Arab-D is outstanding both in terms of porosity and permeability. Ranging from highest quality to the lowest quality, the rock facies consist of: 1. Skeletal Oolitic grainstone and mud packstone. 2. Stromatoporoid-red and green algae-coral rudstone and floatstone. 3. Cladocoropsis rudstone and floatstone. 4. Porous and locally extremely permeable to nonporous dolomite. 5. Bivalve-coated grainintraclast rudstone and floatstone.
6. Micritic to very fine-grained deposits (Robert F. Lindsay). Figure shows East-west seismic depth section, south Ghawar, showing the structure as a drape anticline over a basement fault (Afifi, 2005). These oil rich Jurassic Arab-D reservoirs are effectively sealed under a massive layer of anhydrite. The integrity of the anhydrite top seal is maintained by the in general absence of faults in Arab-D. According to the Klemme’s Basin classification, the Arabian Ghawar field is classified under Class IICa. These are the most important types of heavy oil basins.
The type IICa basins incorporate nearly 18% of the world’s total basin area but they contain nearly half of the world’s total oil and gas reserves (Richard F. Meyer, 2007). The diagram of Klemme basin type IICa. Work Cited Afifi, A. M. (2005). Ghawar: The Anatomy of the World’s Largest Oil Field. Search and Discovery Article #20026 , #20026. Al-Anazi, B. D. (2007, April). What you know about The Ghawar Oil Field ? CSEG RECORDER , 40-43. IAGS. (2004, March 31). New study raises doubts about Saudi oil reserves .
Retrieved March 31, 2009, from Institute for the Analysis of Global Security: http://www. iags. org/n0331043. htm Morton, G. (2004). Trouble in World’s Largest Oil Field-Ghawar. DMD Publishing. Richard F. Meyer, E. D. (2007). Heavy Oil and Natural Bitumen Resources in Geological Basins of the World. Virginia: U. S. Geological Survey. Robert F. Lindsay, D. L. Ghawar Arab-D Reservoir: Porous Shoaling-upward Carbonate Cycles, Saudi Arabia. Dhahran, Saudi Arabia: Saudi Aramco,. US_Energy_Intelligence_Administration. (2008, August). Saudi Arabia Oil Statistics. Retrieved March 31, 2009, from Energy Information Administration, U. S. Government: http://www. eia. doe. gov/emeu/cabs/Saudi_Arabia/Oil. html