Geology and Paleontology
The predominant geologic feature, and the one that makes the McKittrick field distinctive, is the presence of a huge block of Monterey shale – more than 6 mi (9.7 km) long, approximately 1 mi (1.6 km) wide, and up to 2,000 ft (610 m) thick – which slipped off of the slopes of the adjacent Temblor Range during the Pleistocene and moved eastward onto the plain, almost entirely covering the field, and forming an impermeable cap over the oil-bearing rock. This mass of stone, consisting of over 3 cu mi (13 km3) of rock, moved 2 to 3 miles (3.2 to 4.8 km) from its source region, and down about two thousand feet in elevation. While it probably did not move into its present position all at once, the incident must have been dramatic.
Another unusual feature of the McKittrick field is its large tar seeps, points on the surface where petroleum has migrated upwards, forming pools. In California, the McKittrick Tar Pits are second only to the La Brea Tar Pits in fame, and have yielded dozens of skeletons of extinct megafauna with ages from about 10,000 to 40,000 years. The tar seeps outcrop in an area about 4 mi (6.4 km) long, adjacent to the McKittrick Thrust Fault, which defines the southwestern boundary of the oil field. They are found in areas where the overlying Monterey formation, which tumbled down the Temblors during the Pleistocene, eroded away, exposing the oil-bearing strata. When oil reaches the surface, it is exposed to biodegradation, evaporation, and oxidation, forming asphaltum. This series of tar seeps is the most extensive in the state, although none of the individual seeps are as large as the La Brea Tar Pits.
Oil in the McKittrick field is in 13 separate pools: 8 in the Northeast Area, and 5 in the Main Area. The most productive pools have been the Tulare-San Joaquin, Olig, and Basal Reef Ridge in the Main Area, and the Tulare-San Joaquin, Phacoides, and Oceanic in the Northeast Area. Oil API gravity varies between the different pools, with some bearing heavy crude of API gravity 12, and others with lighter oil, such as the Phacoides which reported an average value of 33. Enhanced recovery techniques such as fire flooding and steam flooding have been used since the 1960s to improve recovery of the heavier oils, while water flooding was used in the 1970s and early 1980s in the Phacoides to improve recovery (with limited success, as that pool peaked in 1966).
Major paleontological study of the remains in the tar pits began in 1921 with the first large road cut through the area. Skeletons of many now-extinct mammals have been recovered, including camels, mammoths, dire wolves, saber toothed cats, deer, and bison. Bird species found include ducks, storks, herons, and various shorebirds – mainly species adapted to forage in shallow water.
Read more about this topic: Mc Kittrick Oil Field