Crude oil and natural gas

Petroleum, or crude oil, is an extremely complex mixture derived like coal from prehistoric vegetation. The components range from gaseous to semi-solid or solid hydrocarbons, with compounds of sulphur, nitrogen, oxygen and various metals as impurities. Distillation gives roughly the fractions shown in Table 12.1. The hydrocarbons are almost entirely saturated paraffins, cycloparaffins (naphthenes) and aromatics/polyaromatics the proportions vary enormously from one source to another. 

Methane dissolved in, or trapped above, the oil is referred to as associated gas ethane, propane, etc., are usually also present. Some of this gas separates at the well-head, and must be disengaged. Gas may also be found unassociated with oil. The gas may be wet , containing appreciable amounts of ethane and other hydrocarbons, but gas from the (southern) North Sea is dry , i.e. almost entirely methane. 

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Production of crude oil and natural gas involves technologies that have become increasingly complex as the remaining resources have become more difficult to locate and remove from their subsurface locations. Many new discoveries are made in sediments below the ocean floor in deep-water, and thus require removal of the oil and gas through long water columns. Other situations now require directional drilling of wells so that production involves transfers along wells that arc far from vertical. 

Most petroleum scientists believe that crude oil and natural gas formed over millions to tens of millions of years through the decomposition of organic matter buried by sediments. Generally, marine sediments have led to oil and gas, while freshwater... 

Petroleum engineers are traditionally involved in activities known in the oil industry as the front end of the petroleum fuel cycle (petroleum is either liquid or gaseous hydrocarbons derived from natural deposits—reservoirs—in the earth). These front end activities are namely exploration (locating and proving out the new geological provinces with petroleum reservoirs that may be exploited in the future), and development (the systematic drilling, well completion, and production of economically producible reservoirs). Once the raw petroleum fluids (e.g., crude oil and natural gas) have been produced from the earth, the back end of the fuel cycle takes the produced raw petroleum fluids and refines the.se fluids into useful products. 

Fitzpatrick, M., Common Misconceptions About the RCRA Subtitle C Exemption from Crude Oil and Natural Gas Exploration, Development and Production, Proceedings from the First International Symposium on Oil and Gas Exploration Waste Management Practices, pp. 169-179, 1990. 

The largest releases of polycyclic aromatic hydrocarbons (PAHs) are due to the incomplete combustion of organic compounds during the course of industrial processes and other human activities. Important sources include the combustion of coal, crude oil, and natural gas for both industrial and domestic purposes, the use of such materials in industrial processes (e.g., the smelting of iron ore), the operation of the internal combustion engine, and the combustion of refuse (see Environmental Health Criteria 202, 1998). The release of crude oil into the sea by the offshore oil industry and the wreckage of oil tankers are important sources of PAH in certain areas. Forest hres, which may or may not be the consequence of human activity, are a signihcant... 

This 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 sea floor 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. The remains of the dead organisms are then transformed into crude oil and natural gas. Usually the underground and formation pressure is sufficient for the natural release of hydrocarbon liquids and gases to the surface of the earth. 

Hexanc is a very volatile aliphatic hydrocarbon. It is a constituent in the paraffin fraction of crude oil and natural gas and is also used as an industrial chemical and laboratory reagent. Laboratory grade -hexane contains approximately 99% w-hexane. "Hexane" or "hexanes" is a commercial and industrial product consisting of a mixture of hydrocarbons with six carbon atoms and includes -hexane and its isomers 2-methylpentane and 3-methylpentane as well as small amounts of other hydrocarbons (Brugnone et al. 1991). Laboratory and industrial solvents such as "hexane" and petroleum ether contain -hexane from <0.1% to as much as 33% (Creaser et al. 1983). Information regarding the chemical identity of -hexane is located in Table 3-1. 

Very little information could be identified dealing with -hexane levels in sediments and soils. -Hexane has been identified among the contaminants in an offsite oilfield-disposal pit in New Mexico (Eiceman et al. 1986). Since w-hcxanc is a trace constituent of crude oil and natural gas, as well as a component of refined petroleum products, soil or sediment contamination with -hexane can be expected near oilfield production sites, large soil spills, slush pits and other areas around refineries, and in waste sites where petroleum products or other -hexane-containing wastes had been disposed. Detections would also be likely near many tank storage facilities, pipelines, truck or rail transfer sites, car repair facilities, automobile assembly or storage facilities, and auto and truck fueling facilities (DeLuchi 1993). 

Surfactants can be produced from both petrochemical resources and/or renewable, mostly oleochemical, feedstocks. Crude oil and natural gas make up the first class while palm oil (+kernel oil), tallow and coconut oil are the most relevant representatives of the group of renewable resources. Though the worldwide supplies of crude oil and natural gas are limited—estimated in 1996 at 131 X 1091 and 77 X 109 m3, respectively [28]—it is not expected that this will cause concern in the coming decades or even until the next century. In this respect it should be stressed that surfactant products only represent 1.5% of all petrochemical uses. Regarding the petrochemically derived raw materials, the main starting products comprise ethylene, n-paraffins and benzene obtained from crude oil by industrial processes such as distillation, cracking and adsorption/desorption. The primary products are subsequently converted to a series of intermediates like a-olefins, oxo-alcohols, primary alcohols, ethylene oxide and alkyl benzenes, which are then further modified to yield the desired surfactants. 

The source of these compounds is varied. The butanes are found naturally in crude oils and natural gas. They, plus the olefins, are products of various refinery processes and of olefins plants. They are separated by fractionation, except for butadiene and isobutylene, which are sometimes recovered by extractive distillation. They all vaporize at room temperature, so they are handled in closed, pressurized systems.. 

In addition to conventional crude oil and natural gas, the Province of Alberta, Canada, possesses substantial deposits of oil sands. The location of these deposits are indicated in Figure... 

Kim, Y. Y., and Thompson, R. G., "An Economic Model of New Crude Oil and Natural Gas Supplies in the Lower 48 States," Gulf Publishing Company, Houston, 1978... 

Trends in commercial fuel, eg, fossil fuel, hydroelectric power, nuclear power, production and consumption in the United States and in the Organization of Economic Cooperation and Development (OECD) countries, are shown in Tables 2 and 3. These trends indicate (6,13) (/) a significant resurgence in the production and use of coal throughout the U.S. economy (2) a continued decline in the domestic U.S. production of crude oil and natural gas leading to increased imports of these hydrocarbons (qv) and (5) a continued trend of energy conservation, expressed in terms of energy consumed per... 

Most of the crude oil currently recovered is produced from underground reservoirs. However, surface seepage of crude oil and natural gas is common in many regions. In fact, it is the surface seepage of oil that led to the first use of the high boiling material (bitumen) in the Fertile Crescent. It may also be stated that the presence of active seeps in an area is evidence that oil and gas is still migrating. 

The process of drilling for crude oil and natural gas generates waste drilling fluids or muds, which are often disposed of by land farming. Most of these fluids are water based and contain barite and other metal salts. Thus barium may be introduced into soils as the result of land farming these slurried reserve pit wastes (Bates 1988). 

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