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85-558: Oil roustabout refers to a worker who maintains all things in the oil field . Roustabout is an official classification of natural gas and oil rig personnel. Roustabouts working in oil fields typically perform various jobs requiring little training. Drillers start off as roustabouts until they gain enough hands-on experience to move up to a roughneck or floorhand position, then to driller and rig supervisor. Roustabouts will set up oil well heads, maintain saltwater disposal pumps, lease roads, lease mowing, create dikes around tank batteries on

170-508: A "rouseabout" can be any worker with broad-based, non-specific skills, in any industry. However, rouseabouts or "rousies" most commonly work in rural employment, especially sheep farming , as in the film The Sundowners , where they leave town before the sun goes down. The term was discriminately used in Disney's 1941 animated film Dumbo , during a musical scene in which depicted a group of African-American laborers pulling circus materials off

255-445: 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

340-406: 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

425-407: 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

510-407: A gravity higher than 45 API. Gas cycling is the process where dry gas is injected and produced along with condensed liquid. Kerogen Kerogen is solid, insoluble organic matter in sedimentary rocks . It consists of a variety of organic materials, including dead plants, algae, and other microorganisms, that have been compressed and heated by geological processes. All the kerogen on earth

595-504: A lease, etc. An oil roustabout has no limits in the oil industry and can, and will do any and all oil field work, including roughneck drilling, oil well completion and well service, and even chemical work. An oil field roustabout will also do all things that an oil field pumper would have to do. However, they frequently turn out to be long-term employees and take on more difficult and sometimes dangerous jobs as they gain experience. Most go on to at least become “ roughnecks ” if they work for

680-471: 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

765-435: 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

850-475: A revival of research into the composition, structure, and properties of kerogen. Many studies have documented dramatic and systematic changes in kerogen composition across the range of thermal maturity relevant to the oil and gas industry. Analyses of kerogen are generally performed on samples prepared by acid demineralization with critical point drying , which isolates kerogen from the rock matrix without altering its chemical composition or microstructure. Kerogen

935-523: A shortening of carbon-carbon distances in covalently bonded carbons (related to the transition from primarily aliphatic to primarily aromatic bonding) but a lengthening of carbon-carbon distances in carbons at greater bond separations (related to the formation of kerogen-hosted porosity). This evolution is attributed to the formation of kerogen-hosted pores left behind as segments of the kerogen molecule are cracked off during thermal maturation. These changes in composition and microstructure result in changes in

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1020-502: 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

1105-555: Is Raman spectroscopy . Raman scattering is characteristic of, and can be used to identify, specific vibrational modes and symmetries of molecular bonds. The first-order Raman spectra of kerogen comprises two principal peaks; a so-called G band ("graphitic") attributed to in-plane vibrational modes of well-ordered sp carbon and a so-called D band ("disordered") from symmetric vibrational modes of sp carbon associated with lattice defects and discontinuities. The relative spectral position (Raman shift) and intensity of these carbon species

1190-506: Is a complex mixture of organic chemical compounds that make up the most abundant fraction of organic matter in sedimentary rocks . As kerogen is a mixture of organic materials, it is not defined by a single chemical formula. Its chemical composition varies substantially between and even within sedimentary formations. For example, kerogen from the Green River Formation oil shale deposit of western North America contains elements in

1275-428: 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 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

1360-402: 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

1445-403: 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

1530-452: 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

1615-426: 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

1700-490: 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

1785-452: Is created in surrounding rock by the presence of high heat and pressure in the Earth's crust . Reservoirs are broadly classified as conventional and unconventional reservoirs. In conventional reservoirs, 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

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1870-502: Is estimated to contain 10 tons of carbon. This makes it the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. The type of kerogen present in a particular rock formation depends on the type of organic material that was originally present. Kerogen can be classified by these origins: lacustrine (e.g., algal ), marine (e.g., planktonic ), and terrestrial (e.g., pollen and spores ). The type of kerogen depends also on

1955-403: Is formed during sedimentary diagenesis from the degradation of living matter. The original organic matter can comprise lacustrine and marine algae and plankton and terrestrial higher-order plants. During diagenesis, large biopolymers from, e.g., proteins , lipids , and carbohydrates in the original organic matter, decompose partially or completely. This breakdown process can be viewed as

2040-662: Is generally higher than in other kerogen types, and sulfur is found in substantial amounts in the associated bitumen. Although pyrolysis of type II kerogen yields less oil than type I, the amount yielded is still sufficient for type II-bearing sedimentary deposits to be petroleum source rocks. Similar to type II but with high sulfur content. Type III kerogens are characterized by low initial H/C ratios and high initial O/C ratios. Type III kerogens are derived from terrestrial plant matter, specifically from precursor compounds including cellulose , lignin (a non-carbohydrate polymer formed from phenyl-propane units that binds

2125-577: Is insoluble in normal organic solvents and it does not have a specific chemical formula . Upon heating, kerogen converts in part to liquid and gaseous hydrocarbons. Petroleum and natural gas form from kerogen. The name "kerogen" was introduced by the Scottish organic chemist Alexander Crum Brown in 1906, derived from the Greek for "wax birth" (Greek: κηρός "wax" and -gen, γένεση "birth"). The increased production of hydrocarbons from shale has motivated

2210-431: 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 the globe, on land and offshore. The largest are

2295-740: Is sensitive to sulfur-containing functional groups such as sulfides , thiophenes , and sulfoxides . Sulfur content in kerogen generally decreases with thermal maturity, and sulfur speciation includes a mix of sulfides and thiophenes at low thermal maturities and is further enriched in thiophenes at high maturities. Overall, changes in kerogen composition with respect to heteroatom chemistry occur predominantly at low thermal maturities (bitumen and oil windows), while changes with respect to carbon chemistry occur predominantly at high thermal maturities (oil and gas windows). The microstructure of kerogen also evolves during thermal maturation, as has been inferred by scanning electron microscopy (SEM) imaging showing

2380-630: 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

2465-412: Is shown to correlate to thermal maturity, with kerogens of higher thermal maturity having higher abundance of graphitic/ordered aromatic carbons. Complementary and consistent results have been obtained with infrared (IR) spectroscopy , which show that kerogen has higher fraction of aromatic carbon and shorter lengths of aliphatic chains at higher thermal maturities. These results can be explained by

2550-413: 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

2635-737: Is thought to have formed the terrestrial planets . Kerogenous materials have been detected also in interstellar clouds and dust around stars . The Curiosity rover has detected organic deposits similar to kerogen in mudstone samples in Gale Crater on Mars using a revised drilling technique. The presence of benzene and propane also indicates the possible presence of kerogen-like materials, from which hydrocarbons are derived. Helgeson, H.C.et al. (2009). "A chemical and thermodynamic model of oil generation in hydrocarbon source rocks". Geochim. Cosmochim. Acta. 73 , 594–695. Marakushev, S.A.; Belonogova, O.V. (2021), "An inorganic origin of

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2720-917: 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

2805-612: 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

2890-546: 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

2975-407: 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:

3060-610: 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

3145-410: 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

3230-564: The conversion of aliphatic bonds (such as alicyclic rings) to aromatic bonds. IR spectroscopy is sensitive to carbon-oxygen bonds such as quinones , ketones , and esters , so the technique can also be used to investigate oxygen speciation. It is found that the oxygen content of kerogen decreases during thermal maturation (as has also been observed by elemental analysis), with relatively little observable change in oxygen speciation. Similarly, sulfur speciation can be investigated with X-ray absorption near edge structure (XANES) spectroscopy, which

3315-435: The core out of chlorin -based compounds such as the magnesium in chlorophyll and replace it with their vanadium center in order to attach and harvest energy via light-harvesting complexes . It is theorized that the bacteria contained in worm castings, Rhodopseudomonas palustris , do this during its photoautotrophism mode of metabolism. Over time colonies of light harvesting bacteria solidify, forming kerogen . Kerogen

3400-500: The degree of heat and pressure it has been subjected to, and the length of time the geological processes ran. The result is that a complex mixture of organic compounds reside in sedimentary rocks, serving as the precursor for the formation of hydrocarbons such as oil and gas. In short, kerogen amounts to fossilized organic matter that has been buried and subjected to high temperatures and pressures over millions of years, resulting in various chemical reactions and transformations. Kerogen

3485-438: The different components of kerogen can be identified by microscopic inspection and are classified as macerals . This classification was developed originally for coal (a sedimentary rock that is rich in organic matter of terrestrial origin) but is now applied to the study of other kerogen-rich sedimentary deposits. The Van Krevelen diagram is one method of classifying kerogen by "types", where kerogens form distinct groups when

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3570-654: The formation and/or sedimentation of one or more mineral components resulting in a sedimentary rock like oil shale . When kerogen is contemporaneously deposited with geologic material, subsequent sedimentation and progressive burial or overburden provide elevated pressure and temperature owing to lithostatic and geothermal gradients in Earth's crust. Resulting changes in the burial temperatures and pressures lead to further changes in kerogen composition including loss of hydrogen , oxygen , nitrogen , sulfur , and their associated functional groups , and subsequent isomerization and aromatization Such changes are indicative of

3655-402: 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

3740-407: 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 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

3825-406: The kerogen-rich source rock (i.e. the source rock is also the reservoir rock). Much of the porosity in these shales is found to be hosted within the kerogen, rather than between mineral grains as occurs in conventional reservoir rocks. Thus, kerogen controls much of the storage and transport of oil and gas in shale. Another possible method of formation is that vanabin -containing organisms cleave

3910-484: The largest quantity of hydrocarbons upon pyrolysis . Hence, from the theoretical view, shales containing type I kerogen are the most promising deposits in terms of conventional oil retorting. Type II kerogens are characterized by intermediate initial H/C ratios and intermediate initial O/C ratios. Type II kerogen is principally derived from marine organic materials, which are deposited in reducing sedimentary environments. The sulfur content of type II kerogen

3995-425: The lead character Chad is often referred to as a roustabout. Roughnecks and Roustabouts is the second album by Pete Williams, formerly bassist and vocalist with Dexys Midnight Runners , and currently performing as The Pete Williams Band. In the sci-fi short story Big Sam Was My Friend , Harlan Ellison refers to roustabout robots as "roustabots". In a 1995 episode of BBC TV comedy series "Bottom" titled "Hole",

4080-434: 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

4165-438: 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

4250-1141: The nature of the minerals surrounding different particles. Measurements performed with atomic force microscopy coupled to infrared spectroscopy (AFM-IR) and correlated with organic petrography have analyzed the evolution of the chemical composition and mechanical properties of individual macerals of kerogen with thermal maturation at the nanoscale. These results indicate that all macerals decrease in oxygen content and increase in aromaticity (decrease in aliphalicity) during thermal maturation, but some macerals undergo large changes while other macerals undergo relatively small changes. In addition, macerals that are richer in aromatic carbon are mechanically stiffer than macerals that are richer in aliphatic carbon, as expected because highly aromatic forms of carbon (such as graphite) are stiffer than highly aliphatic forms of carbon (such as wax). Labile kerogen breaks down to generate principally liquid hydrocarbons (i.e., oil ), refractory kerogen breaks down to generate principally gaseous hydrocarbons, and inert kerogen generates no hydrocarbons but forms graphite . In organic petrography,

4335-412: The nature of the product, with lower thermal maturities yielding mainly bitumen/oil and higher thermal maturities yielding gas. These generated species are partially expelled from the kerogen-rich source rock and in some cases can charge into a reservoir rock. Kerogen takes on additional importance in unconventional resources , particularly shale. In these formations, oil and gas are produced directly from

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4420-438: 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

4505-436: 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 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

4590-724: 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

4675-406: 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,

4760-431: 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

4845-444: The preferential removal of aliphatic carbons by cracking reactions during pyrolysis, where the cracking typically occurs at weak C–C bonds beta to aromatic rings and results in the replacement of a long aliphatic chain with a methyl group. At higher maturities, when all labile aliphatic carbons have already been removed—in other words, when the kerogen has no remaining oil-generation potential—further increase in aromaticity can occur from

4930-412: The presence of abundant internal pore networks within the lattice of thermally mature kerogen. Analysis by gas sorption demonstrated that the internal specific surface area of kerogen increases by an order of magnitude (~ 40 to 400 m /g) during thermal maturation. X-ray and neutron diffraction studies have examined the spacing between carbon atoms in kerogen, revealing during thermal maturation

5015-429: 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

5100-485: 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

5185-471: The properties of kerogen. For example, the skeletal density of kerogen increases from approximately 1.1 g/ml at low thermal maturity to 1.7 g/ml at high thermal maturity. This evolution is consistent with the change in carbon speciation from predominantly aliphatic (similar to wax, density < 1 g/ml) to predominantly aromatic (similar to graphite, density > 2 g/ml) with increasing thermal maturity. Additional studies have explored

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5270-447: The proportions carbon 215 : hydrogen 330 : oxygen 12 : nitrogen 5 : sulfur 1. Kerogen is insoluble in normal organic solvents in part because of the high molecular weight of its component compounds. The soluble portion is known as bitumen . When heated to the right temperatures in the earth's crust , ( oil window c. 50–150  °C , gas window c. 150–200 °C, both depending on how quickly

5355-406: The ratios of hydrogen to carbon and oxygen to carbon are compared. Type I kerogens are characterized by high initial hydrogen-to-carbon (H/C) ratios and low initial oxygen-to-carbon (O/C) ratios. This kerogen is rich in lipid-derived material and is commonly, but not always, from algal organic matter in lacustrine (freshwater) environments. On a mass basis, rocks containing type I kerogen yield

5440-491: 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

5525-408: 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

5610-409: 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

5695-414: The reverse of photosynthesis . These resulting units can then polycondense to form geopolymers . The formation of geopolymers in this way accounts for the large molecular weights and diverse chemical compositions associated with kerogen. The smallest units are the fulvic acids , the medium units are the humic acids , and the largest units are the humins . This polymerization usually happens alongside

5780-417: The rig company for more than a few months. An early 2010 survey by Careercast.com of the best and worst jobs based on five criteria—environment, income, employment outlook, physical demands and stress—rated 'roustabout' as the worst job. Nonetheless, the anecdotal and subjective experience of an actual roustabout suggests that for some, it can be a challenging, adventurous job. In Australia and New Zealand

5865-496: The right shows the organic carbon cycle with the flow of kerogen (black solid lines) and the flow of biospheric carbon (green solid lines), showing both the fixation of atmospheric CO 2 by terrestrial and marine primary productivity . The combined flux of reworked kerogen and biospheric carbon into ocean sediments constitutes total organic carbon burial entering the endogenous kerogen pool. Carbonaceous chondrite meteorites contain kerogen-like components. Such material

5950-410: 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

6035-419: 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 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

6120-560: The source rock is heated) some types of kerogen release crude oil or natural gas , collectively known as hydrocarbons ( fossil fuels ). When such kerogens are present in high concentration in rocks such as organic-rich mudrocks shale , they form possible source rocks . Shales that are rich in kerogen but have not been heated to required temperature to generate hydrocarbons instead may form oil shale deposits. The chemical composition of kerogen has been analyzed by several forms of solid state spectroscopy. These experiments typically measure

6205-410: 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

6290-490: The spatial heterogeneity of kerogen at small length scales. Individual particles of kerogen arising from different inputs are identified and assigned as different macerals . This variation in starting material may lead to variations in composition between different kerogen particles, leading to spatial heterogeneity in kerogen composition at the micron length scale. Heterogeneity between kerogen particles may also arise from local variations in catalysis of pyrolysis reactions due to

6375-432: The speciations (bonding environments) of different types of atoms in kerogen. One technique is C NMR spectroscopy , which measures carbon speciation. NMR experiments have found that carbon in kerogen can range from almost entirely aliphatic ( sp hybridized ) to almost entirely aromatic ( sp hybridized ), with kerogens of higher thermal maturity typically having higher abundance of aromatic carbon. Another technique

6460-428: The strings of cellulose together); terpenes and phenols . Coal is an organic-rich sedimentary rock that is composed predominantly of this kerogen type. On a mass basis, type III kerogens generate the lowest oil yield of principal kerogen types. Type IV kerogen comprises mostly inert organic matter in the form of polycyclic aromatic hydrocarbons . They have no potential to produce hydrocarbons. The diagram on

6545-454: 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

6630-452: 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

6715-549: The thermal maturity state of kerogen. Aromatization allows for molecular stacking in sheets, which in turn drives changes in physical characteristics of kerogen, such as increasing molecular density, vitrinite reflectance , and spore coloration (yellow to orange to brown to black with increasing depth/thermal maturity). During the process of thermal maturation , kerogen breaks down in high-temperature pyrolysis reactions to form lower-molecular-weight products including bitumen, oil, and gas. The extent of thermal maturation controls

6800-469: The train for construction. Roustabout was a 1964 musical movie starring Elvis Presley , Barbara Stanwyck , and Joan Freeman , in a story set in a traveling carnival — for which Presley recorded the song titled "Roustabout". Farley Granger 's character, Arthur "Bowie" Bowers, in Nicholas Ray 's 1948 film noir They Live By Night , tells Catherine "Keeetchie" Mobley ( Cathy O'Donnell ) that he

6885-539: The two main characters Richie and Eddie are deliberately left at the very top of a fairground ferris wheel, after Richie sexually approached the attendant. When it is noticed they are the only ones on the ride and left up there, Richie goes into a rant referring to those on the ground below as roustabouts. Oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter)

6970-407: 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

7055-431: 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

7140-442: 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

7225-431: Was a roustabout with a circus. The term is used in the song " The Mariner's Revenge Song ", by The Decemberists . "Roustabout" is also the name of a song recorded by the bluegrass band, Open Road , on their album Lucky Drive . The term is also used by Beats Antique for two songs on their album Collide . The Slamball team Rousties is named after a roustabout. In the musical theater production All Shook Up ,

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