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120-796: The Oxnard Oil Field is a large and productive oil field in and adjacent to the city of Oxnard , in Ventura County, California in the United States. Its conventional oil reserves are close to exhaustion, with only an estimated one percent of the original oil recoverable with current technology remaining: 434,000 barrels (69,000 m) out of an original 43.5 million. However, the reservoir includes an enormous deposit of tar sands, ultra-heavy oil classed as an unconventional petroleum reserve, and potentially containing 600 million barrels (95,000,000 m) of oil equivalent, should it become economically feasible to extract. Present operators on

240-542: A broader aridification trend. The EMCI ended 18 million years ago, giving way to the Middle Miocene Warm Interval (MMWI), the warmest part of which was the MMCO that began 16 million years ago. As the world transitioned into the MMCO, carbon dioxide concentrations varied between 300 and 500 ppm. Global annual mean surface temperature during the MMCO was about 18.4 °C. MMCO warmth was driven by

360-445: A cap rock) is a fundamental part of the trap that prevents hydrocarbons from further upward migration. A capillary seal is formed when the capillary pressure across the pore throats is greater than or equal to the buoyancy pressure of the migrating hydrocarbons. They do not allow fluids to migrate across them until their integrity is disrupted, causing them to leak. There are two types of capillary seal whose classifications are based on

480-529: A clade of large terrestrial predatory crocodyliformes distantly related to modern crocodilians, from which they likely diverged over 180 million years ago, are known from the Miocene of South America. The last Desmostylians thrived during this period before becoming the only extinct marine mammal order. The pinnipeds , which appeared near the end of the Oligocene, became more aquatic. A prominent genus

600-406: A consequence, oil and natural gas are often found together. In common usage, deposits rich in oil are known as oil fields, and deposits rich in natural gas are called natural gas fields. In general, organic sediments buried in depths of 1,000 m to 6,000 m (at temperatures of 60 ° C to 150 °C) generate oil, while sediments buried deeper and at higher temperatures generate natural gas. The deeper

720-570: A cooler, drier climate. C 4 grasses, which are able to assimilate carbon dioxide and water more efficiently than C 3 grasses, expanded to become ecologically significant near the end of the Miocene between 6 and 7 million years ago, although they did not expand northward during the Late Miocene. The expansion of grasslands and radiations among terrestrial herbivores correlates to fluctuations in CO 2 . One study, however, has attributed

840-512: A depleted reservoir than to treat and release it on the surface. In 2008 only two wells remained active in the deep McInnes reservoir; all the others were in the shallow tar sands. Under the California Department of Conservation well adoption rule, Tri-Valley Oil & Gas Company acquired 20 wells formerly operated by defunct GEO Petroleum, Inc., which filed for Chapter 11 bankruptcy protection in 1998. Wells declared deserted by

960-407: A few, very large offshore drilling rigs, due to the cost and logistical difficulties in working over water. Rising gas prices in the early 21st century encouraged drillers to revisit fields that previously were not considered economically viable. For example, in 2008 McMoran Exploration passed a drilling depth of over 32,000 feet (9754 m) (the deepest test well in the history of gas production) at

1080-486: A good analogue for future warmer climates caused by anthropogenic global warming , with this being especially true of the global climate during the Middle Miocene Climatic Optimum (MMCO), because the last time carbon dioxide levels were comparable to projected future atmospheric carbon dioxide levels resulting from anthropogenic climate change was during the MMCO. The Ross Sea margin of

1200-435: A good model for a "living fossil". Eucalyptus fossil leaves occur in the Miocene of New Zealand , where the genus is not native today, but have been introduced from Australia . Both marine and continental fauna were fairly modern, although marine mammals were less numerous. Only in isolated South America and Australia did widely divergent fauna exist. In Eurasia, genus richness shifted southward to lower latitudes from

1320-491: A gravity higher than 45 API. Gas cycling is the process where dry gas is injected and produced along with condensed liquid. Miocene The Miocene ( / ˈ m aɪ . ə s iː n , - oʊ -/ MY -ə-seen, -⁠oh- ) is the first geological epoch of the Neogene Period and extends from about 23.03 to 5.333 million years ago (Ma). The Miocene was named by Scottish geologist Charles Lyell ;

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1440-598: A major expansion of Antarctic glaciers. This severed the connection between the Indian Ocean and the Mediterranean Sea and formed the present land connection between Afro-Arabia and Eurasia. The subsequent uplift of mountains in the western Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea (known as the Messinian salinity crisis ) near

1560-480: A major expansion of grass-grazer ecosystems . Herds of large, swift grazers were hunted by predators across broad sweeps of open grasslands , displacing desert, woodland, and browsers . The higher organic content and water retention of the deeper and richer grassland soils , with long-term burial of carbon in sediments, produced a carbon and water vapor sink. This, combined with higher surface albedo and lower evapotranspiration of grassland, contributed to

1680-471: A result of changes in the structure of the subsurface from processes such as folding and faulting , leading to the formation of domes , anticlines , and folds. Examples of this kind of trap are an anticline trap, a fault trap, and a salt dome trap. They are more easily delineated and more prospective than their stratigraphic counterparts, with the majority of the world's petroleum reserves being found in structural traps. Stratigraphic traps are formed as

1800-435: A result of lateral and vertical variations in the thickness, texture, porosity, or lithology of the reservoir rock. Examples of this type of trap are an unconformity trap, a lens trap and a reef trap. Hydrodynamic traps are a far less common type of trap. They are caused by the differences in water pressure, that are associated with water flow, creating a tilt of the hydrocarbon-water contact. The seal (also referred to as

1920-602: A significant drop in atmospheric carbon dioxide levels. Both continental and oceanic thermal gradients in mid-latitudes during the Early Miocene were very similar to those in the present. Global cooling caused the East Asian Summer Monsoon (EASM) to begin to take on its modern form during the Early Miocene. From 22.1 to 19.7 Ma, the Xining Basin experienced relative warmth and humidity amidst

2040-700: A significant local decline along the northeastern coast of Australia during the Tortonian, most likely due to warming seawater. Cetaceans attained their greatest diversity during the Miocene, with over 20 recognized genera of baleen whales in comparison to only six living genera. This diversification correlates with emergence of gigantic macro-predators such as megatoothed sharks and raptorial sperm whales . Prominent examples are O. megalodon and L. melvillei . Other notable large sharks were O. chubutensis , Isurus hastalis , and Hemipristis serra . Crocodilians also showed signs of diversification during

2160-502: A significantly higher displacement pressure such that the pressure required for tension fracturing is actually lower than the pressure required for fluid displacement—for example, in evaporites or very tight shales. The rock will fracture when the pore pressure is greater than both its minimum stress and its tensile strength then reseal when the pressure reduces and the fractures close. Unconventional (oil & gas) reservoirs are accumulations where oil and gas phases are tightly bound to

2280-651: A zone of low rainfall in the Late Miocene. The Indian Plate continued to collide with the Eurasian Plate , creating new mountain ranges and uplifting the Tibetan Plateau , resulting in the rain shadowing and aridification of the Asian interior. The Tian Shan experienced significant uplift in the Late Miocene, blocking westerlies from coming into the Tarim Basin and drying it as a result. At

2400-400: Is also influential in creating traps for hydrocarbons. Where the sedimentary rocks are sandstones with high porosity, and the structure and stratigraphy allow hydrocarbons to be trapped on their upward migration, oilfields are found. As the oil field is in the center of a large flat alluvial floodplain, there is no surface expression of any anticlinal structure capable of holding oil. Under

2520-405: Is an area of accumulated liquid petroleum underground in multiple (potentially linked) reservoirs, trapped as it rises to impermeable rock formations. In industrial terms, an oil field implies that there is an economic benefit worthy of commercial attention. Oil fields may extend up to several hundred kilometers across the surface, meaning that extraction efforts can be large and spread out across

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2640-402: Is analogous to saying that the oil which can be extracted forms within the source rock itself, as opposed to accumulating under a cap rock. Oil sands are an example of an unconventional oil reservoir. Unconventional reservoirs and their associated unconventional oil encompass a broad spectrum of petroleum extraction and refinement techniques, as well as many different sources. Since the oil

2760-411: Is around 15 inches (380 mm), almost all in the winter, and all in the form of rain. The mean annual temperature is 56 to 60 °F (16 °C); freezes occur rarely. Elevations on the field range from about 40 to 60 feet (18 m) above sea level. It is mostly flat, with a very gentle slope to the south-southeast; drainage is along Revolon Slough to Calleguas Creek to Mugu Lagoon , and then to

2880-403: Is being pursued at a higher rate because of the scarcity of conventional reservoirs around the world. After the discovery of a reservoir, a petroleum engineer will seek to build a better picture of the accumulation. In a simple textbook example of a uniform reservoir, the first stage is to conduct a seismic survey to determine the possible size of the trap. Appraisal wells can be used to determine

3000-452: Is best to manage the gas cap effectively, that is, placing the oil wells such that the gas cap will not reach them until the maximum amount of oil is produced. Also a high production rate may cause the gas to migrate downward into the production interval. In this case, over time the reservoir pressure depletion is not as steep as in the case of solution-based gas drive. In this case, the oil rate will not decline as steeply but will depend also on

3120-426: Is called the stock tank oil initially in place . As a result of studying factors such as the permeability of the rock (how easily fluids can flow through the rock) and possible drive mechanisms, it is possible to estimate the recovery factor, or what proportion of oil in place can be reasonably expected to be produced. The recovery factor is commonly 30–35%, giving a value for the recoverable resources. The difficulty

3240-417: Is clustered together in a drilling island near the northeast corner of the intersection of Rose Avenue and Wooley Road. The total productive area of the field projected to the surface is 1,350 acres (546 ha). The climate in the region is Mediterranean , with cool, rainy winters and warm, rainless summers, in which the heat is moderated by frequent morning coastal low clouds and fog. Annual precipitation

3360-490: Is contained within the source rock, unconventional reservoirs require that the extracting entity function as a mining operation rather than drilling and pumping like a conventional reservoir. This has tradeoffs, with higher post-production costs associated with complete and clean extraction of oil being a factor of consideration for a company interested in pursuing a reservoir. Tailings are also left behind, increasing cleanup costs. Despite these tradeoffs, unconventional oil

3480-649: Is shared between Iran and Qatar . The second largest natural gas field is the Urengoy gas field , and the third largest is the Yamburg gas field , both in Russia . Like oil, natural gas is often found underwater in offshore gas fields such as the North Sea , Corrib Gas Field off Ireland , and near Sable Island . The technology to extract and transport offshore natural gas is different from land-based fields. It uses

3600-413: Is that reservoirs are not uniform. They have variable porosities and permeabilities and may be compartmentalized, with fractures and faults breaking them up and complicating fluid flow. For this reason, computer modeling of economically viable reservoirs is often carried out. Geologists, geophysicists, and reservoir engineers work together to build a model that allows simulation of the flow of fluids in

3720-940: Is usually necessary to drill into the Earth's crust, although surface oil seeps exist in some parts of the world, such as the La Brea Tar Pits in California and numerous seeps in Trinidad . Factors that affect the quantity of recoverable hydrocarbons in a reservoir include the fluid distribution in the reservoir, initial volumes of fluids in place, reservoir pressure, fluid and rock properties, reservoir geometry, well type, well count, well placement, development concept, and operating philosophy. Modern production includes thermal , gas injection , and chemical methods of extraction to enhance oil recovery. A virgin reservoir may be under sufficient pressure to push hydrocarbons to

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3840-481: The International Commission on Stratigraphy : Regionally, other systems are used, based on characteristic land mammals; some of them overlap with the preceding Oligocene and following Pliocene Epochs: Continents continued to drift toward their present positions. Of the modern geologic features, only the land bridge between South America and North America was absent, although South America

3960-559: The Middle Miocene Climate Transition (MMCT). Abrupt increases in opal deposition indicate this cooling was driven by enhanced drawdown of carbon dioxide via silicate weathering. The MMCT caused a sea surface temperature (SST) drop of approximately 6 °C in the North Atlantic. The drop in benthic foraminiferal δ O values was most noticeable in the waters around Antarctica, suggesting cooling

4080-545: The Old World . Around the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees and had begun following their own evolutionary path during the final Messinian Stage (7.5–5.3 Ma) of the Miocene. As in the Oligocene before it, grasslands continued to expand, and forests to dwindle. In the seas of the Miocene, kelp forests made their first appearance and soon became one of Earth's most productive ecosystems. The plants and animals of

4200-560: The aquatic ecosystem , which is usually a sea but might also be a river, lake, coral reef, or algal mat , the formation of an oil or gas reservoir also requires a sedimentary basin that passes through four steps: Timing is also an important consideration; it is suggested that the Ohio River Valley could have had as much oil as the Middle East at one time, but that it escaped due to a lack of traps. The North Sea , on

4320-407: The buoyancy forces driving the upward migration of hydrocarbons through a permeable rock cannot overcome the capillary forces of a sealing medium. The timing of trap formation relative to that of petroleum generation and migration is crucial to ensuring a reservoir can form. Petroleum geologists broadly classify traps into three categories that are based on their geological characteristics:

4440-560: The carbon cycle occurred approximately 6 Ma, causing continental carbon reservoirs to no longer expand during cold spells, as they had done during cold periods in the Oligocene and most of the Miocene. At the end of the Miocene, global temperatures rose again as the amplitude of Earth's obliquity increased, which caused increased aridity in Central Asia. Around 5.5 Ma, the EAWM underwent a period of rapid intensification. Life during

4560-671: The Blackbeard site in the Gulf of Mexico. ExxonMobil 's drill rig there had reached 30,000 feet by 2006, without finding gas, before it abandoned the site. Crude oil is found in all oil reservoirs formed in the Earth's crust from the remains of once-living things. Evidence indicates that millions of years of heat and pressure changed the remains of microscopic plants and animals into oil and natural gas. Roy Nurmi, an interpretation adviser for Schlumberger oil field services company, described

4680-710: The Central Paratethys, cut off from sources of freshwater input by its separation from the Eastern Paratethys. From 13.36 to 12.65 Ma, the Central Paratethys was characterised by open marine conditions, before the reopening of the Bârlad Strait resulted in a shift to brackish-marine conditions in the Central Paratethys, causing the Badenian-Sarmatian Extinction Event. As a result of the Bârlad Strait's reopening,

4800-837: The Early to the Middle Miocene. Europe's large mammal diversity significantly declined during the Late Miocene. In the Early Miocene, several Oligocene groups were still diverse, including nimravids , entelodonts , and three-toed equids. As in the previous Oligocene Epoch, oreodonts were still diverse, only to disappear in the earliest Pliocene. During the later Miocene mammals were more modern, with easily recognizable canids , bears , red pandas , procyonids , equids , beavers , deer , camelids , and whales , along with now-extinct groups like borophagine canids , certain gomphotheres , three-toed horses , and hornless rhinos like Teleoceras and Aphelos . The late Miocene also marks

4920-720: The East Antarctic Ice Sheet (EAIS) was highly dynamic during the Early Miocene. The Miocene began with the Early Miocene Cool Event (Mi-1) around 23 million years ago, which marked the start of the Early Miocene Cool Interval (EMCI). This cool event occurred immediately after the Oligocene-Miocene Transition (OMT) during a major expansion of Antarctica's ice sheets, but was not associated with

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5040-601: The East Asian Winter Monsoon (EAWM) became stronger synchronously with a southward shift of the subarctic front. Greenland may have begun to have large glaciers as early as 8 to 7 Ma, although the climate for the most part remained warm enough to support forests there well into the Pliocene. Zhejiang, China was noticeably more humid than today. In the Great Rift Valley of Kenya , there

5160-460: The LMC; extratropical sea surface temperatures dropped substantially by approximately 7–9 °C. 41 kyr obliquity cycles became the dominant orbital climatic control 7.7 Ma and this dominance strengthened 6.4 Ma. Benthic δ O values show significant glaciation occurred from 6.26 to 5.50 Ma, during which glacial-interglacial cycles were governed by the 41 kyr obliquity cycle. A major reorganisation of

5280-579: The Late Cretaceous, are known from the Miocene of Patagonia, represented by the mole-like Necrolestes . The youngest known representatives of metatherians (the broader grouping to which marsupials belong) in Europe, Asia and Africa are known from the Miocene, including the European herpetotheriid Amphiperatherium , the peradectids Siamoperadectes and Sinoperadectes from Asia, and

5400-653: The Late Miocene, the Earth's climate began to display a high degree of similarity to that of the present day . The 173 kyr obliquity modulation cycle governed by Earth's interactions with Saturn became detectable in the Late Miocene. By 12 Ma, Oregon was a savanna akin to that of the western margins of the Sierra Nevada of northern California . Central Australia became progressively drier, although southwestern Australia experienced significant wettening from around 12 to 8 Ma. The South Asian Winter Monsoon (SAWM) underwent strengthening ~9.2–8.5 Ma. From 7.9 to 5.8 Ma,

5520-508: The McInnes, Lucas, and Livingston pools were brought online, producing oil of API gravity 24, 32 and 25-36 respectively. Waterflooding operations in these deeper reservoirs in the 1960s assisted production, but most wells in these horizons were abandoned as the last economically recoverable oil was extracted; a few remained as water disposal wells, as it is usually both economically and environmentally preferable to reinject wastewater back into

5640-676: The Mediterranean Sea to almost completely evaporate. This event is referred to as the " Messinian salinity crisis ". Then, at the Miocene–Pliocene boundary, the Strait of Gibraltar opened, and the Mediterranean refilled. That event is referred to as the " Zanclean flood ". Also during the early Miocene (specifically the Aquitanian and Burdigalian Stages), the apes first evolved, began diversifying, and became widespread throughout

5760-574: The Miocene Epoch was mostly supported by the two newly formed biomes , kelp forests and grasslands . Grasslands allow for more grazers, such as horses , rhinoceroses , and hippos . Ninety-five percent of modern plants existed by the end of this epoch . Modern bony fish genera were established. A modern-style latitudinal biodiversity gradient appeared ~15 Ma. The coevolution of gritty , fibrous, fire-tolerant grasses and long-legged gregarious ungulates with high-crowned teeth , led to

5880-590: The Miocene were recognizably modern. Mammals and birds were well established. Whales , pinnipeds , and kelp spread. The Miocene is of particular interest to geologists and palaeoclimatologists because major phases of the geology of the Himalaya occurred during that epoch, affecting monsoonal patterns in Asia, which were interlinked with glacial periods in the northern hemisphere. The Miocene faunal stages from youngest to oldest are typically named according to

6000-449: The Miocene. The largest form among them was a gigantic caiman Purussaurus which inhabited South America. Another gigantic form was a false gharial Rhamphosuchus , which inhabited modern age India . A strange form, Mourasuchus also thrived alongside Purussaurus . This species developed a specialized filter-feeding mechanism, and it likely preyed upon small fauna despite its gigantic size. The youngest members of Sebecidae ,

6120-550: The North American Great Plains and in Argentina . The global trend was towards increasing aridity caused primarily by global cooling reducing the ability of the atmosphere to absorb moisture, particularly after 7 to 8 million years ago. Uplift of East Africa in the late Miocene was partly responsible for the shrinking of tropical rain forests in that region, and Australia got drier as it entered

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6240-656: The Oligocene–Miocene transgression. As the southern Andes rose in the Middle Miocene (14–12 million years ago) the resulting rain shadow originated the Patagonian Desert to the east. Far northern Australia was monsoonal during the Miocene. Although northern Australia is often believed to have been much wetter during the Miocene, this interpretation may be an artefact of preservation bias of riparian and lacustrine plants; this finding has itself been challenged by other papers. Western Australia, like today,

6360-457: The Oxnard city limits. This Canadian firm accepted waste from other oil field operators, mostly brine, and injects it thousands of feet into the ground. This permit held by Anterra will expire in 2018 and the commercial oil disposal sites in agricultural land are no longer permitted by county zoning law. The county Board of Supervisors eliminated such a use in farmland two years after the 1998 permit

6480-602: The Pacific Ocean. The Oxnard field is within the Ventura Basin Province of southern California. Geologically, this area is part of a structural downwarp that occurred during the late Pliocene . Rocks within the region are all sedimentary and mostly marine. Oil accumulations, of which there are many in the Ventura province, mainly occur in anticlinal settings modified by faulting; stratigraphy

6600-617: The Qiongdongnan Basin in the northern South China Sea indicates the Pearl River was a major source of sediment flux into the sea during the Early Miocene and was a major fluvial system as in the present. During the Oligocene and Early Miocene, the coast of northern Brazil, Colombia, south-central Peru , central Chile and large swathes of inland Patagonia were subject to a marine transgression . The transgressions in

6720-539: The State ;– typically due to the dissolution of the operator – are open to adoption and redevelopment under the "orphan well" rule, with the written consent of the owner of the mineral rights to the property as well as the State Department of Oil, Gas, and Geothermal Resources. In 2008 Tri-Valley began redeveloping these wells and bringing them back to production. Oil produced in the field goes to

6840-497: The activity of the Columbia River Basalts and enhanced by decreased albedo from the reduction of deserts and expansion of forests. Climate modelling suggests additional, currently unknown, factors also worked to create the warm conditions of the MMCO. The MMCO saw the expansion of the tropical climatic zone to much larger than its current size. The July ITCZ, the zone of maximal monsoonal rainfall, moved to

6960-410: The actual capacity. Laboratory testing can determine the characteristics of the reservoir fluids, particularly the expansion factor of the oil, or how much the oil expands when brought from the high pressure and high temperature of the reservoir to a "stock tank" at the surface. With such information, it is possible to estimate how many "stock tank" barrels of oil are located in the reservoir. Such oil

7080-449: The area. In addition to extraction equipment, there may be exploratory wells probing the edges to find more reservoir area, pipelines to transport the oil elsewhere, and support facilities. Oil fields can occur anywhere that the geology of the underlying rock allows, meaning that certain fields can be far away from civilization, including at sea. Creating an operation at an oil field can be a logistically complex undertaking, as it involves

7200-472: The aridity of the former. Unequivocally-recognizable dabbling ducks , plovers , typical owls , cockatoos and crows appear during the Miocene. By the epoch's end, all or almost all modern bird groups are believed to have been present; the few post-Miocene bird fossils which cannot be placed in the evolutionary tree with full confidence are simply too badly preserved, rather than too equivocal in character. Marine birds reached their highest diversity ever in

7320-638: The beginning of the Miocene, the northern margin of the Arabian plate, then part of the African landmass, collided with Eurasia; as a result, the Tethys seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish – Arabian region. The first step of this closure occurred 20 Ma, reducing water mass exchange by 90%, while the second step occurred around 13.8 Ma, coincident with

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7440-577: The course of this epoch . The youngest representatives of Choristodera , an extinct order of aquatic reptiles that first appeared in the Middle Jurassic , are known from the Miocene of Europe, belonging to the genus Lazarussuchus , which had been the only known surviving genus of the group since the beginning of the Eocene. The last known representatives of the archaic primitive mammal order Meridiolestida , which dominated South America during

7560-488: The current level when the permit expires. The Santa Clara Wastewater Facility , established in 1959 about 2 miles (3.2 km) southwest of Santa Paula , accepted such waste but without injection wells on site until it closed in 2014. 34°11′53″N 119°08′09″W  /  34.1980°N 119.1357°W  / 34.1980; -119.1357 Oil field Reservoirs are broadly classified as conventional and unconventional reservoirs. In conventional reservoirs,

7680-578: The end of the Miocene due to increased habitat uniformity. The expansion of grasslands in North America also led to an explosive radiation among snakes. Previously, snakes were a minor component of the North American fauna, but during the Miocene, the number of species and their prevalence increased dramatically with the first appearances of vipers and elapids in North America and the significant diversification of Colubridae (including

7800-422: The end of the Miocene. The Paratethys underwent a significant transgression during the early Middle Miocene. Around 13.8 Ma, during a global sea level drop, the Eastern Paratethys was cut off from the global ocean by the closure of the Bârlad Strait, effectively turning it into a saltwater lake. From 13.8 to 13.36 Ma, an evaporite period similar to the later Messinian salinity crisis in the Mediterranean ensued in

7920-637: The enigmatic Saint Bathans Mammal . Microbial life in the igneous crust of the Fennoscandian Shield shifted from being dominated by methanogens to being primarily composed of sulphate-reducing prokaryotes . The change resulted from fracture reactivation during the Pyrenean-Alpine orogeny, enabling sulphate-reducing microbes to permeate into the Fennoscandian Shield via descending surficial waters. Diatom diversity

8040-430: The equipment associated with extraction and transportation, as well as infrastructure such as roads and housing for workers. This infrastructure has to be designed with the lifespan of the oil field in mind, as production can last many years. Several companies, such as Hill International , Bechtel , Esso , Weatherford International , Schlumberger , Baker Hughes and Halliburton , have organizations that specialize in

8160-461: The evolution of both groups into modern representatives. The early Miocene Saint Bathans Fauna is the only Cenozoic terrestrial fossil record of the landmass, showcasing a wide variety of not only bird species, including early representatives of clades such as moa , kiwi and adzebills , but also a diverse herpetofauna of sphenodontians , crocodiles and turtles as well as a rich terrestrial mammal fauna composed of various species of bats and

8280-499: The expansion of grasslands not to a CO 2 drop but to the increasing seasonality and aridity, coupled with a monsoon climate, which made wildfires highly prevalent compared to before. The Late Miocene expansion of grasslands had cascading effects on the global carbon cycle, evidenced by the imprint it left in carbon isotope records. Cycads between 11.5 and 5 million years ago began to rediversify after previous declines in variety due to climatic changes, and thus modern cycads are not

8400-718: The extinction of the last-surviving members of the hyaenodonts . Islands began to form between South and North America in the Late Miocene, allowing ground sloths like Thinobadistes to island-hop to North America. The expansion of silica-rich C 4 grasses led to worldwide extinctions of herbivorous species without high-crowned teeth . Mustelids diversified into their largest forms as terrestrial predators like Ekorus , Eomellivora , and Megalictis and bunodont otters like Enhydriodon and Sivaonyx appeared. Eulipotyphlans were widespread in Europe, being less diverse in Southern Europe than farther north due to

8520-481: The extremely viscous petroleum deposits in the producing formation, which they named after their firm – the Pliocene "Vaca" Tar Sand – they were able to produce about 50 barrels per day (7.9 m/d). In May of that same year they discovered tar sands in the underlying Monterey Formation from which they were able to produce about 90 barrels (14 m) of oil per day. More adventurous drillers found deeper producing horizons with lighter oil. In 1953 and 1954

8640-501: The field include Tri-Valley Oil & Gas Co., Anterra Energy Services, Inc., Chase Production Co., and Occidental Petroleum through its Vintage Production subsidiary. As of the beginning of 2009, there were 34 active wells on the field. The Oxnard Oil Field is one of several beneath the Oxnard Plain , an area mostly protected agricultural land with the communities of Ventura , Oxnard, and Camarillo separated by greenbelts. In

8760-402: The field on the north; California State Route 34 (Oxnard's East 5th Street) cuts across it from east to west, and Rice Avenue crosses it from north to south. Most of the currently active oil wells are in the eastern portion of the field, west of the intersection of 5th Street and Pleasant Valley Road. Some active wells remain west of Rice Avenue, and a group of wells using directional drilling

8880-574: The field. The quality of the oil from the lower pools is good and the gravity medium, at 24 to 38 API , while the oil from the tar sand is extremely heavy and of poor quality, with an extraordinarily high sulfur content – API gravity of 5-7, viscosity of 28,000 to 33,000 centipoise , and sulfur content of between 5 and 7.5 percent by weight. The field was discovered in January 1937 by Vaca Oil Exploration Co., which drilled into tar sands about 2,800 feet (850 m) below ground surface. In spite of

9000-629: The findings of marine invertebrate fossils of both Atlantic and Pacific affinity in La Cascada Formation . Connection would have occurred through narrow epicontinental seaways that formed channels in a dissected topography . The Antarctic Plate started to subduct beneath South America 14 million years ago in the Miocene, forming the Chile Triple Junction . At first the Antarctic Plate subducted only in

9120-402: The gas bubbles drive the oil to the surface. The bubbles then reach critical saturation and flow together as a single gas phase. Beyond this point and below this pressure, the gas phase flows out more rapidly than the oil because of its lowered viscosity. More free gas is produced, and eventually the energy source is depleted. In some cases depending on the geology the gas may migrate to the top of

9240-684: The globe, on land and offshore. The largest are the Ghawar Field in Saudi Arabia and the Burgan Field in Kuwait , with more than 66 to 104 billion barrels (9.5×10 m ) estimated in each. In the modern age, the location of oil fields with proven oil reserves is a key underlying factor in many geopolitical conflicts. Natural gas originates by the same geological thermal cracking process that converts kerogen to petroleum. As

9360-464: The human lineage) appeared in Africa at the very end of the Miocene, including Sahelanthropus , Orrorin , and an early form of Ardipithecus ( A. kadabba ). The chimpanzee–human divergence is thought to have occurred at this time. The evolution of bipedalism in apes at the end of the Miocene instigated an increased rate of faunal turnover in Africa. In contrast, European apes met their end at

9480-606: The lake levels of the Eastern Paratethys dropped as it once again became a sea. The Fram Strait opened during the Miocene and acted as the only throughflow for Atlantic Water into the Arctic Ocean until the Quaternary period. Due to regional uplift of the continental shelf, this water could not move through the Barents Seaway in the Miocene. The modern day Mekong Delta took shape after 8 Ma. Geochemistry of

9600-575: The large-scale construction of the infrastructure to support oil field exploitation. The term "oilfield" can be used as a shorthand to refer to the entire petroleum industry . However, it is more accurate to divide the oil industry into three sectors: upstream ( crude oil production from wells and separation of water from oil ), midstream (pipeline and tanker transport of crude oil) and downstream ( refining of crude oil to products, marketing of refined products, and transportation to oil stations). More than 65,000 oil fields are scattered around

9720-434: The liquid sections applying extra pressure. This is present in the reservoir if there is more gas than can be dissolved in the reservoir. The gas will often migrate to the crest of the structure. It is compressed on top of the oil reserve, as the oil is produced the cap helps to push the oil out. Over time the gas cap moves down and infiltrates the oil, and the well will produce more and more gas until it produces only gas. It

9840-438: The location of oil-water contact and with it the height of the oil bearing sands. Often coupled with seismic data, it is possible to estimate the volume of an oil-bearing reservoir. The next step is to use information from appraisal wells to estimate the porosity of the rock. The porosity of an oil field, or the percentage of the total volume that contains fluids rather than solid rock, is 20–35% or less. It can give information on

9960-627: The name comes from the Greek words μείων ( meíōn , "less") and καινός ( kainós , "new") and means "less recent" because it has 18% fewer modern marine invertebrates than the Pliocene has. The Miocene followed the Oligocene and preceded the Pliocene. As Earth went from the Oligocene through the Miocene and into the Pliocene, the climate slowly cooled towards a series of ice ages . The Miocene boundaries are not marked by distinct global events but by regionally defined transitions from

10080-403: The naturally occurring hydrocarbons, such as crude oil ( petroleum ) or natural gas , are trapped by overlying rock formations with lower permeability , while in unconventional reservoirs the rocks have high porosity and low permeability, which keeps the hydrocarbons trapped in place, therefore not requiring a cap rock . Reservoirs are found using hydrocarbon exploration methods. An oil field

10200-547: The north, increasing precipitation over southern China whilst simultaneously decreasing it over Indochina during the EASM. Western Australia was at this time characterised by exceptional aridity. In Antarctica, average summer temperatures on land reached 10 °C. In the oceans, the lysocline shoaled by approximately half of a kilometre during warm phases that corresponded to orbital eccentricity maxima. The MMCO ended around 14 million years ago, when global temperatures fell in

10320-438: The oil and form a secondary gas cap. Some energy may be supplied by water, gas in water, or compressed rock. These are usually minor contributions with respect to hydrocarbon expansion. By properly managing the production rates, greater benefits can be had from solution-gas drives. Secondary recovery involves the injection of gas or water to maintain reservoir pressure. The gas/oil ratio and the oil production rate are stable until

10440-523: The origin of many modern genera such as Nerodia , Lampropeltis , Pituophis and Pantherophis ). Arthropods were abundant, including in areas such as Tibet where they have traditionally been thought to be undiverse. Neoisopterans diversified and expanded into areas they previously were absent from, such as Madagascar and Australia. In the oceans, brown algae , called kelp , proliferated, supporting new species of sea life, including otters , fish and various invertebrates . Corals suffered

10560-724: The other hand, endured millions of years of sea level changes that successfully resulted in the formation of more than 150 oil fields. Although the process is generally the same, various environmental factors lead to the creation of a wide variety of reservoirs. Reservoirs exist anywhere from the land surface to 30,000 ft (9,000 m) below the surface and are a variety of shapes, sizes, and ages. In recent years, igneous reservoirs have become an important new field of oil exploration, especially in trachyte and basalt formations. These two types of reservoirs differ in oil content and physical properties like fracture connectivity, pore connectivity, and rock porosity . A trap forms when

10680-406: The placement of the well with respect to the gas cap. As with other drive mechanisms, water or gas injection can be used to maintain reservoir pressure. When a gas cap is coupled with water influx, the recovery mechanism can be highly efficient. Water (usually salty) may be present below the hydrocarbons. Water, as with all liquids, is compressible to a small degree. As the hydrocarbons are depleted,

10800-463: The possible herpetotheriid Morotodon from the late Early Miocene of Uganda. Approximately 100 species of apes lived during this time , ranging throughout Africa, Asia and Europe and varying widely in size, diet, and anatomy. Due to scanty fossil evidence it is unclear which ape or apes contributed to the modern hominid clade, but molecular evidence indicates this ape lived between 18 and 13 million years ago. The first hominins ( bipedal apes of

10920-431: The preferential mechanism of leaking: the hydraulic seal and the membrane seal. A membrane seal will leak whenever the pressure differential across the seal exceeds the threshold displacement pressure, allowing fluids to migrate through the pore spaces in the seal. It will leak just enough to bring the pressure differential below that of the displacement pressure and will reseal. A hydraulic seal occurs in rocks that have

11040-429: The pressure. As the reservoir depletes, the pressure falls below the bubble point , and the gas comes out of solution to form a gas cap at the top. This gas cap pushes down on the liquid helping to maintain pressure. This occurs when the natural gas is in a cap below the oil. When the well is drilled the lowered pressure above means that the oil expands. As the pressure is reduced it reaches bubble point, and subsequently

11160-485: The process as follows: Plankton and algae, proteins and the life that's floating in the sea, as it dies, falls to the bottom, and these organisms are going to be the source of our oil and gas. When they're buried with the accumulating sediment and reach an adequate temperature, something above 50 to 70 °C they start to cook. This transformation, this change, changes them into the liquid hydrocarbons that move and migrate, will become our oil and gas reservoir. In addition to

11280-491: The reduction in pressure in the reservoir allows the water to expand slightly. Although this unit expansion is minute, if the aquifer is large enough this will translate into a large increase in volume, which will push up on the hydrocarbons, maintaining pressure. With a water-drive reservoir, the decline in reservoir pressure is very slight; in some cases, the reservoir pressure may remain unchanged. The gas/oil ratio also remains stable. The oil rate will remain fairly stable until

11400-462: The relatively impermeable Conejo -Topanga Formation, which caps the faulted anticlinal structure containing medium-grade oil about 6,500 feet (2,000 m) below ground surface. This producing horizon is named the "McInnes" pool, and is in the Oligocene -age Sespe Formation . The Oxnard field contains a large quantity of tar sand , a type of bitumen which is categorized as an unconventional oil deposit. The average depth below ground surface of

11520-408: The reservoir pressure drops below the bubble point when critical gas saturation is reached. When the gas is exhausted, the gas/oil ratio and the oil rate drops, the reservoir pressure has been reduced, and the reservoir energy is exhausted. In reservoirs already having a gas cap (the virgin pressure is already below bubble point), the gas cap expands with the depletion of the reservoir, pushing down on

11640-409: The reservoir, leading to an improved estimate of the recoverable resources. Reserves are only the part of those recoverable resources that will be developed through identified and approved development projects. Because the evaluation of reserves has a direct impact on the company or the asset value, it usually follows a strict set of rules or guidelines. To obtain the contents of the oil reservoir, it

11760-410: The rock fabric by strong capillary forces, requiring specialised measures for evaluation and extraction. Unconventional reservoirs form in completely different ways to conventional reservoirs, the main difference being that they do not have "traps". This type of reservoir can be driven in a unique way as well, as buoyancy might not be the driving force for oil and gas accumulation in such reservoirs. This

11880-504: The small (2,800-barrel (450 m)-per-day) Oxnard Refinery, owned by Tenby, Inc., in an unincorporated area south of Fifth Street near the eastern Oxnard city limit. This refinery also processes oil from the West Montalvo field on the coast directly west of the Oxnard field. Between 1950 and 1981 Mandalay Bay was a permitted oil field waste disposal site which caused the release of numerous hazardous chemicals. The records of what

12000-410: The source, the "drier" the gas (that is, the smaller the proportion of condensates in the gas). Because both oil and natural gas are lighter than water, they tend to rise from their sources until they either seep to the surface or are trapped by a non-permeable stratigraphic trap. They can be extracted from the trap by drilling. The largest natural gas field is South Pars/Asalouyeh gas field, which

12120-714: The southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the Strait of Magellan . As the southern part of Nazca Plate and the Chile Rise became consumed by subduction the more northerly regions of the Antarctic Plate begun to subduct beneath Patagonia so that the Chile Triple Junction advanced to the north over time. The asthenospheric window associated to the triple junction disturbed previous patterns of mantle convection beneath Patagonia inducing an uplift of ca. 1 km that reversed

12240-454: The structural trap, the stratigraphic trap, and the far less common hydrodynamic trap . The trapping mechanisms for many petroleum reservoirs have characteristics from several categories and can be known as a combination trap. Traps are described as structural traps (in deformed strata such as folds and faults) or stratigraphic traps (in areas where rock types change, such as unconformities, pinch-outs and reefs). Structural traps are formed as

12360-745: The surface alluvium , a series of relatively impermeable sedimentary units cap the petroleum-bearing formation. On top are the Pleistocene San Pedro and Pleistocene-upper Pliocene Santa Barbara formations ; under that the Pico Sands , of Pliocene age, which contain areas of tar sands ; under that, separated by an unconformity, the Monterey Formation , of Miocene age, which also contains tar sands (the Vaca Tar Sand); under that, again separated by an unconformity,

12480-401: The surface to date, although Tri-Valley Corporation is actively developing the unit by drilling horizontal wells through the sands and subjecting them to the cyclic steam process. According to Tri-Valley, some of the test wells have shown production rates of 1,000 barrels per day (160 m/d), and can be brought online as soon as the steam generators and storage infrastructure are in place on

12600-452: The surface. As the fluids are produced, the pressure will often decline, and production will falter. The reservoir may respond to the withdrawal of fluid in a way that tends to maintain the pressure. Artificial drive methods may be necessary. This mechanism (also known as depletion drive) depends on the associated gas of the oil. The virgin reservoir may be entirely semi-liquid but will be expected to have gaseous hydrocarbons in solution due to

12720-545: The tar sands – both the Vaca Sand, and the Pico Sand ;– is about 2,500 feet (760 m), and their thickness ranges from 0 to 600 feet (180 m), representing a total volume of 405,000 acre-feet (500,000,000 m), equivalent to approximately 565 million barrels (89,800,000 m) of oil for both units, were it possible to recover their petroleum content. Only a tiny fraction of this has been brought to

12840-431: The vicinity of the oil field, agriculture remains the predominant land use, and oil wells, processing facilities, and associated infrastructure are interspersed with fields planted with crops such as strawberries, broccoli, and onions. Parts of the field, particularly on the west, have been given over to light industrial and commercial development as the Oxnard metropolitan area expands to the east. U.S. Highway 101 bounds

12960-474: The warmer Oligocene to the cooler Pliocene Epoch. During the Early Miocene, Afro-Arabia collided with Eurasia, severing the connection between the Mediterranean and Indian Oceans, and allowing the interchange of fauna between Eurasia and Africa, including the dispersal of proboscideans and hominoids into Eurasia. During the late Miocene, the connections between the Atlantic and Mediterranean closed, causing

13080-407: The water begins to be produced along with the oil, the recovery rate may become uneconomical owing to the higher lifting and water disposal costs. If the natural drives are insufficient, as they very often are, then the pressure can be artificially maintained by injecting water into the aquifer or gas into the gas cap. The force of gravity will cause the oil to move downward of the gas and upward of

13200-431: The water reaches the well. In time, the water cut will increase, and the well will be watered out. The water may be present in an aquifer (but rarely one replenished with surface water ). This water gradually replaces the volume of oil and gas that is produced out of the well, given that the production rate is equivalent to the aquifer activity. That is, the aquifer is being replenished from some natural water influx. If

13320-442: The water. If vertical permeability exists then recovery rates may be even better. These occur if the reservoir conditions allow the hydrocarbons to exist as a gas. Retrieval is a matter of gas expansion. Recovery from a closed reservoir (i.e., no water drive) is very good, especially if bottom hole pressure is reduced to a minimum (usually done with compressors at the wellhead). Any produced liquids are light-colored to colorless, with

13440-604: The west coast of South America are thought to be caused by a regional phenomenon while the steadily rising central segment of the Andes represents an exception. While there are numerous registers of Oligocene–Miocene transgressions around the world it is doubtful that these correlate. It is thought that the Oligocene–Miocene transgression in Patagonia could have temporarily linked the Pacific and Atlantic Oceans, as inferred from

13560-423: Was Allodesmus . A ferocious walrus , Pelagiarctos may have preyed upon other species of pinnipeds including Allodesmus . Furthermore, South American waters witnessed the arrival of Megapiranha paranensis , which were considerably larger than modern age piranhas . New Zealand 's Miocene fossil record is particularly rich. Marine deposits showcase a variety of cetaceans and penguins , illustrating

13680-624: Was a gradual and progressive trend of increasing aridification, though it was not unidirectional, and wet humid episodes continued to occur. Between 7 and 5.3 Ma, temperatures dropped sharply again in the Late Miocene Cooling (LMC), most likely as a result of a decline in atmospheric carbon dioxide and a drop in the amplitude of Earth's obliquity, and the Antarctic ice sheet was approaching its present-day size and thickness. Ocean temperatures plummeted to near-modern values during

13800-591: Was approaching the western subduction zone in the Pacific Ocean , causing both the rise of the Andes and a southward extension of the Meso-American peninsula. Mountain building took place in western North America , Europe , and East Asia . Both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in

13920-464: Was arid, particularly so during the Middle Miocene. Climates remained moderately warm, although the slow global cooling that eventually led to the Pleistocene glaciations continued. Although a long-term cooling trend was well underway, there is evidence of a warm period during the Miocene when the global climate rivalled that of the Oligocene . The climate of the Miocene has been suggested as

14040-446: Was dumped were subsequently lost, resulting in calls for an investigation and millions of dollars in lawsuits from home buyers who were told the area was safe for habitation. Anterra operates the only commercial facility that disposes oil field waste through injection wells in the county. In 1998, Anadime Energy Services Inc. applied for permission from the county of Ventura to operate a commercial disposal site at 1933 E. Wooley Road near

14160-688: Was inversely correlated with carbon dioxide levels and global temperatures during the Miocene. Most modern lineages of diatoms appeared by the Late Miocene. There is evidence from oxygen isotopes at Deep Sea Drilling Program sites that ice began to build up in Antarctica about 36 Ma during the Eocene . Further marked decreases in temperature during the Middle Miocene at 15 Ma probably reflect increased ice growth in Antarctica. It can therefore be assumed that East Antarctica had some glaciers during

14280-441: Was issued. They also denied a zoning change in 2015 that would have allowed expansion of the facility citing the many places of open space and industrial zones where the oil field disposal sites are permitted. They were unconvinced by the testimony that Ventura County, as the third-largest oil-producing region in the state, needs to allow brines to be disposed of effectively and cheaply. Anterra can still apply to continue operations at

14400-646: Was most intense there. Around this time the Mi3b glacial event (a massive expansion of Antarctic glaciers) occurred. The East Antarctic Ice Sheet (EAIS) markedly stabilised following the MMCT. The intensification of glaciation caused a decoherence of sediment deposition from the 405 kyr eccentricity cycle. The MMWI ended about 11 Ma, when the Late Miocene Cool Interval (LMCI) started. A major but transient warming occurred around 10.8-10.7 Ma. During

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