Concept Of Drilling For Crude Oil example essay topic

Petroleum, or crude oil, is a naturally occurring oily liquid composed ofvarious organic chemicals. It is found in large quantities below the surface of the earth and is used as a fuel and as a raw material in the chemical industry. Modern industrial societies use it primarily to achieve a degreeof mobility on land, at sea, and in the air that was barely imaginable less than a hundred years ago. In addition, petroleum and its derivatives are used in the manufacture of medicines and fertilizers, foodstuffs, plastic ware, building materials, paints, and cloth and to generate electricity. In fact, modern industrial civilization depends on petroleum and its products; the physical structure and way of life of the suburban communities that surround the great cities are the result of an ample and inexpensive supply of petroleum. In addition, the goals of developing countries to exploit their natural resources and to supply foodstuffs for the underdeveloped populations, are based on the assumption of petroleum availability.

In recent years, however, the worldwide availability ofpetroleum has steadily declined and its relative cost has increased. Petroleum will probably no longer be a common commercial material bythe mid-21st century. Characteristics The chemical composition of all petroleum is principally hydrocarbons. Petroleum contains gaseous, liquid, and solid elements. The consistency ofpetroleum varies from liquid as thin as gasoline to liquid so thick that it will barely pour. Formation Petroleum is formed under the earth's surface by the decomposition of marine organisms.

The remains of tiny organisms that live in the sea and, to a lesser extent, those of land organisms that are carried down to these in rivers and of plants that grow on the ocean bottoms, are mixed withthe fine sands and silts that settle to the bottom in quiet sea basins. Such deposits, which are rich in organic materials, become the source rocks forthe making of crude oil. Th process began many millions of years ago with the development of abundant life, and it continues to this day. The sediments grow thicker and sink into the seafloor under their own weight. As additional deposits pile up, the pressure on the ones below increases several thousand times, and the temperature rises by several hundred degrees. The mud and sand harden into shale and sandstone; carbonate precipitates and skeletal shells harden into limestone; and the remains ofthe dead organisms are transformed into crude oil and natural gas.

Once the petroleum forms, it flows upward in the earth's crust because ith as a low density. The crude oil and natural gas rise into the microscopic pores of the coarser sediments lying above. Frequently, the rising material encounters a dense layer of rock that prevents further movement. In other words, the oil has become trapped, and a reservoir of petroleum is formed. A significant amount of the upward-migrating oil, however, does not encounter impermeable rock but instead flows out at the surface of the earth or onto the ocean floor. Historical Development These surface deposits of crude oil have been known to humans for thousands of years.

In the areas where they occurred, they were long used for such limited purposes as caulking boats, waterproofing cloth and fueling torches. By the time of the Renaissance, some surface deposits were being distilled to obtain lubricants and medicinal products, but the real exploitation of crude oil did not begin until the 19th century. The Industrial Revolution had by then brought about a search for new fuels, and the social changes it effected had produced a need for good, cheap oil for lamps. People wished to be able to work and read after dark. The search for a better lamp fuel led to a great demand for rock oil, that is, crude oil, and various scientists in the mid-19th century we redeveloping processes to make commercial use of it. Thus the quest for greater supplies of crude oil began.

For several years people had known that wells drilled for water and salt occasionally contained petroleum, so the concept of drilling for crude oil itself soon followed. The first such wells were dug in Germany in 1857-59, but the event that gained world fame was the drilling of an oil well near Oil Creek, Pennsylvania, by Colonel Edwin L. Drake in 1859. Exploration In order to find crude oil underground, geologists must search for a sedimentary basin in which shales rich in organic material have been buried for a sufficiently long time for petroleum to have formed. The petroleum must also have had an opportunity to migrate into porous traps that are capable of holding large amounts of fluid. The occurrence ofcrude oil in the earth's crust is limited both by these conditions, which must be met simultaneously, and by the time span of tens of millions to hundred million years required for the oil's formation. Petroleum geologists and geophysicists, however, have many tools at their disposal to assist in identifying potential areas for drilling.

Thus, surface mapping of sedimentary beds makes possible the interpretation of subsurface features, which can then be supplemented with information obtained by drilling into the crust and retrieving samples of the rock layers encountered. In addition, increasingly sophisticated scientific techniques, having to do with the reflection and refraction of sound waves propagated through the earth, reveal details of the structure and interrelationship ofvarious layers in the subsurface. Ultimately, however, the only way to prove that oil is present in the subsurface is to drill a well. An oil field, once found, may comprise more than one reservoir, that is, more than one single, continuous, bounded accumulation of oil. Indeed, several reservoirs may be stacked one above the other, isolated by intervening shales and impervious rock. Such reservoirs may vary in size from a few tens of hectares to tens of square kilometers, and from a few meters in thickness to several hundred or more.

Most of the oil that has been discovered and exploited in the world has been found in a relatively few large reservoirs. In the U.S., for example, 60 of approximately 10,000 oil fields have accounted for half of the productive capacity and reserves. Primary Production Most oil wells in the U.S. are drilled by the rotary method that was first described in a British patent in 1844 assigned to R. Be art. In rotary drilling, the drill string, a series of connected pipes, is supported by a derrick. The string is rotated by being coupled to the rotating table on the derrick floor. The drill bit at the end of the string is generally designed with three cone-shaped wheels tipped with hardened teeth.

Drill cuttings are lifted continually to the surface by a circulating-fluid system driven by pump. Trapped crude oil is under pressure. Thus, when a well bore is drilled into this pressured accumulation of oil, the oil expands into the low-pressure sink created by the well bore in communication with the earth's surface. As the well fills up with fluid, however, a back pressure is exerted on the reservoir, and the flow of additional fluid into the well bore would soon stop, were no other conditions involved.

Most crude oils, however, contain significant amount of natural gas in solution, and this gas is kept in solution by the high pressure in the reservoir. The gas comes out of solution when the low pressure in the well bore is encountered and the gas, once liberated, immediately begins to expand. This expansion, together with the dilution of the column of oil by the less dense gas, results in the transporting of oil up to the earth's surface. The fluid may not reach the surface, so that a pump (artificial lift) must be installed in the well bore to continue producing the crude oil.

Eventually, the flow rate of the crude oil becomes so small, and the cost of lifting the oil to the surface becomes so great, that the well costs more to operate than the revenues that can be gained from selling the crude oil. The well's economic limit has then been reached and it is abandoned. Oil Drill Rig and Reservoir The rotary drilling rig uses a series of rotating pipes, called the drill string, to tap into oil reservoirs. The drill string is supported by a derrick, and turned by the rotary table on its floor. Circulating, mud like fluid driven by a pump removes cuttings as the teeth of the drill bit dig into the rock around the reservoir. Reservoirs occur in many places.

They form as a result of intense pressure on top of layers of dead marine and land organisms mixed with sand or silt. This reservoir abuts a salt dome, which has trapped a layer of oil and natural gas between itself and nonporous rock. Because they have no place to expand, the gas and crude oil are under high pressure and will tend to rush explosively out the channel opened by the drill rig. Enhanced Oil Recovery The oil industry has developed schemes for supplementing the production of crude oil that can be obtained mostly by taking advantage of the natural reservoir energy. Such supplementary schemes, collectively known as enhanced oil recovery technology, can increase the recovery ofcrude oil, but only at the additional cost of supplying extraneous energy tothe reservoir. In this way, the recovery of crude oil has been increased toan overall average of 33 percent of the original oil.

Two successful supplementary schemes are in use at this time: water injection and steam injection. Water Injection In a completely developed oil field, the wells may be drilled anywhere from 60 to 600 m (200 to 2000 ft) from one another, depending on the nature of the reservoir. If water is pumped into alternate wells in such afield, the pressure in the reservoir as a whole can be maintained or even increased. In this way the rate of production of the crude oil also can be increased; in addition, the water physically displaces the oil, thus increasing the recovery efficiency. In some reservoirs with a high degreeof uniformity and little clay content, water flooding may increase therecovery efficiency to as much as 60 percent or more of the original oil in place.

Water flooding was first introduced in the Pennsylvania oil fields, more or less accidentally, in the late 19th century, and it has since spread throughout the world. Steam Injection Steam injection is used in reservoirs that contain very viscous oils, those that are thick and flow slowly. The steam not only provides a source of energy to displace the oil, it also causes a marked reduction in viscosity (by raising the temperature of the reservoir), so that the crude oil flows faster under any given pressure. This scheme has been used extensively inthe states of California, in the United States, and of Zu lia, in Venezuela, where large reservoirs exist that contain viscous oil. Offshore Drilling Another method to increase oil-field production and one of the most exciting engineering achievements in recent decades has been the construction and operation of offshore drilling rigs. The drilling rigs a reinstalled, operated, and serviced on an offshore platform in water up to a depth of several hundred meters; the platform may either float or sit on legs planted on the ocean floor, where it is capable of resisting waves, wind, and in Arctic regions ice floes.

Refining Once oil has been produced from an oil field, it is treated with chemicals and heat to remove water and solids, and the natural gas is separated. The oil is then stored in a tank, or battery of tanks, and later transported to a refinery by truck, railroad tank car or pipeline. Large oil fields all have direct outlets to major, common-carrier pipelines. Basic Distillation The basic refining tool is the distillation unit. In the U.S., after the Civil War, more than 100 still refineries were already in operation.

Crude oil begins to vaporize at a temperature somewhat less than that required to boil water. Hydrocarbons with the lowest molecular weight vaporize at the lowest temperatures, whereas successively higher temperatures are required to distill larger molecules. The first material to be distilled from crude oil is the gasoline fraction, followed in turn by naphtha and then by kerosine. The residue in the kettle, in the old still refineries, was then treated with caustic and sulfuric acid, and finally steam distilled thereafter. Lubricants and distillate fuel oils were obtained from the upper regions and waxes and asphalt from the lower regions of the distillation apparatus. In the later 19th century the gasoline and naphtha fractions were actually considered a nuisance because little need for them existed, and the demand for kerosine also began to decline because of the growing production of electricity and the use of electric lights.

With the introduction of the automobile, however, the demand for gasoline suddenly burgeoned, and the need for greater supplies of crude oil increased accordingly. Oil Refining and Fractional Distillation Crude oil is refined into products such as gasoline, asphalt, and waxes by a process called fractional distillation. During the process, the parts, or fractions, of crude oil are divided out successively by their increasing molecular weight. For instance, gasoline has a low molecular weight and vaporizes at a fairly low temperature. This means that at the appropriate temperature, while all of the rest of the oil is still in liquid form, gasoline may be separated out. The remaining oil goes through the same process at a slightly higher temperature, and jet fuel is divided out.

Repeating the distillation process several times will separate out several constituents of crude oil, which are then processed and put to a wide range of uses. Product Percentages In 1920 a U.S. barrel of crude oil, containing 42 gallons, yielded 11 gallons of gasoline, 5.3 gallons of kerosine, 20.4 gallons of gas oil and distillates, and 5.3 gallons of heavier distillates. In recent years, by contrast, the yield of crude oil has increased to almost 21 gallons of gasoline, 3 gallons of jet fuel, 9 gallons of gas oil and distillates, and somewhat less than 4 gallons of lubricants and 3 gallons of heavier residues. Petroleum Engineering The studies and tasks carried out by petroleum engineers are drawn from virtually every field of science and engineering. Thus the exploration staffs include geologists who specialize in surface mapping in order to try to reconstruct the subsurface configuration of the various sedimentary strata that will provide clues to the presence of petroleum traps.

Subsurface specialists then study drill cuttings and interpret data on the subsurface formations that is relayed to surface recorders from electrical, sonic, and nuclear logging devices lowered into the bore hole on a wireline. Seismologists interpret sophisticated signals returning to the surface from sound waves that are propagated through the earth's crust. Geochemist's study the transformation of organic matter and the means for detecting and predicting the occurrence of such matter in subsurface strata. In addition, physicists, chemists, biologists, and mathematicians all support the basic research and development of sophisticated exploration techniques. Petroleum engineers are responsible for the development of discovered oil accumulations. They usually specialize in one of the important categories of production operation: drilling and surface facilities, petro physical and geological analysis of the reservoir, reserve estimation and specification of optimal development practices, or production control and surveillance.

Although many of these specialists have formal training as petroleum engineers, many others are drawn from the ranks of chemical, mechanical, electrical, and civil engineers; physicists, chemists, and mathematicians; and geologists. Production Volumes and Reserves Crude oil is perhaps the most useful and versatile raw material that has become available for exploitation. By 1995, the United States was using 7 billion barrels of petroleum per year, and worldwide consumption ofpetroleum was 25 billion barrels per year. Reserves The world's technically recoverable reserves of crude oil the amount of oil that experts are certain of being able to extract without regard to cost from the earth add up to about 2300 billion barrels, of which some 110 billion barrels are in the United States. However, only a small fraction of this can be extracted at current prices.

Of the known oil reserves that cane profitably extracted at current prices, more than half are in the Middle East; only 2 percent are in the United States. Projections It is likely that some additional discoveries will be made of new reserves in coming years, and new technologies will be developed that permit therecovery efficiency from already known resources to be increased. The supply of crude oil will at any rate extend into the early decades of the 21st century. Virtually no expectation exists among experts, however, that discoveries and inventions will extend the availability of cheap crude oil much beyond that period. For example, the Prudhoe Bay field on the North Slope of Alaska is the largest field ever discovered in the western hemisphere. The ultimate recovery of crude oil from this field is anticipated to be about 10 billion barrels, which is sufficient to supply the current needs of the U.S. for less than two years, but only one such field was discovered in the West in more than a century of exploration.

Furthermore, drilling activity has not halted the steady decline of U.S. crude oil reserves that began during the 1970's. Alternatives The only alternative fuel that is capable of supplying the huge energy needs of today's world is coal, the availability of which in the U.S. and elsewhere throughout the world is well established. Associated with its projected increased utilization would be an increase in the use of coal-based electrical power to do more and more of the chores of industrialized nations.