Traps anticlinal
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Most of the world's oil deposits are found trapped in upward folds in rock called anticlines. Oil accumulates in these structures when impermeable rock above traps oil and gas that has migrated upward from its source rock. The document describes various geological processes that can form anticlines, such as igneous intrusions, settling of sediments, salt tectonics, and deposition along an uneven seafloor. It then analyzes several major oil fields around the world defined by anticline traps, including Ghawar in Saudi Arabia, the largest oil field, and Burgan in Kuwait, once the highest producing field.
Traps anticlinal
- 1. Traps: Anticlinal Most of the world's known oil deposits are trapped in anticlines. (About 80%) Origin of Folds: 1. Igneous Intrusions may arch overlying rock. An unusually symmetrical dome, thought to be the result of laccolithic intrusion.
- 2. 2. Settling or subsidence may produce folds, providing that it is differential in character. 3. When soluble rocks occur in the section, leaching followed by slumping may produce sagging in the overlying strata, with arching over the blocks that have not collapsed. 4. Residual structural highs may also possibly result from the plastic flow of salt. 5. Horizontal movements are at their maximum in orogenic belts where the earth's crust is under compression. Pseudo-Folds, so called because they look like folds but are not the result of any movement, are formed by deposition parallel to an uneven ocean floor. If the deposition is from suspension, and the slopes are not steeper than the angle of repose of the unconsolidated sediment, the layers may be deposited with initial dips which conform to the topography of the submerged surface. Anticlines come in all sizes. The length varies from less than a mile to many miles and the amount of closure ranges from tens of feet to thousands of feet. As a general rule, the larger anticlines do not carry oil the entire length. Instead, the superimposed domes or nodes are oil-bearing and the intervening saddles contain only water. The larger anticlines are also less likely to be filled with hydrocarbons to the spill point.
- 3. Trap Case Study 1-San Pedro field, Argentina. Location: In Salta Province in northern Argentina. Type: (Elongate Anticline) It occurs along the crest of a partly eroded, tightly folded anticline which makes a ridge in the San Antonio range. Beginning: 1921 Discovery well: 1928 Commercial production: 1930 2-Ghawar Oil Field, Saudi Arabia. It is one of the largest oil fields in the world. It is the result of the merger of five oil fields along a great anticlinal arch. Type: Elongate Anticline.
- 5. 3-Cumberland Oil Field, Oklahoma, U.S.A. Location: Lies on the south flank of the Arbuckle Mountain system in southern Oklahoma. Type: (Anticline) A closed faulted anticline which lies within a down-faulted block of sedimentary rock. Discovery well: 1940 4-Cymric Oil Field, California, U.S.A. Location: Lies in Kern County, California, on the west side of the San Joaquin Valley. Type: (Anticline) it is elliptical in plan and unusually symmetrical. Discovery well: 1916 5-Rangely Field, Colorado. Location: Lies in northwestern Colorado on the northeastern edge of the Unita basin. Type: (Anticline) Asymmetrical. Beginning: 1878 Discovery well: 1902 6-Augusta Field, Kansas, U.S.A. Location: Lies in Butler County, Kansas, extending from 3 miles north of the city of Augusta to 7 miles south of it.
- 6. Type: (Anticline) divided by a saddle into the north Augusta and south Augusta. First well: 1914 7-Bahrain Field, Bahrain. Location: Lies in the central part of Bahrain Island, which lies at the mouth of the bay between Qatar Peninsula and the mainland of Saudi Arabia. Type: (Anticline) Elliptical in plan. Size: 12 miles long and 4 miles wide. Production: 32000 barrels a day during 1957 Commercial production: 1932 8-Santa Fe Springs Oil Field, California, U.S.A. Location: Lies in Los Angeles County, about 12 miles southeast of the center of the city of Los Angeles. Type: (Dome) an unusually elliptical dome. Area: 1500 acres.
- 7. Discovery well: 1919 9-Big Lake Pool, Texas, U.S.A. Location: Lies in the southwestern corner of Regan County, in west Texas. Type: (Dome) Discovery well: 1923 10- San Joaquin Field, Venezuela. Location: Lies in the central part of the state of Anzoátegui, in eastern Venezuela. Type: (Dome) Beginning: 1934 Discovery well: 1936 Commercial production: 1939 11- Burgan Field, Kuwait. It, along with the adjoining Magwa and Ahmadi fields, has for some years been the largest source of petroleum in the world, with a daily output of over one million barrels. Type: (Dome) Faulted elliptical dome with the major axis trending almost north-south. Size: 15 miles long and 10 miles wide. Beginning: 1932 Discovery well: 1938 Commercial production: 1945