Thermal Cracking
In an effort to increase the yield from distillation, the thermal cracking process was developed. In this process, the heavier portions of the crude oil were heated under pressure and at higher temperatures. This resulted in the large hydrocarbon molecules being split into smaller ones, so that the yield of gasoline from a barrel of crude oil was increased. The efficiency of the process was limited, however, because at the high temperatures and pressures that were used, a large amount of coke was deposited in the reactors. This in turn required the use of still higher temperatures and pressures to crack the crude oil. A coking process was then invented in which fluids were recirculated; the process ran for a much longer time, with far less buildup of coke. Many refiners quickly adopted the process of thermal cracking.
Alkylation and Catalytic Cracking
Two additional basic processes, alkylation and catalytic cracking, were introduced in the 1930s and further increased the gasoline yield from a barrel of crude oil. In alkylation small molecules produced by thermal cracking are recombined in the presence of a catalyst. This produces branched molecules in the gasoline boiling range that have superior properties for example, higher antiknock ratings as a fuel for high-powered engines such as those used in today s commercial planes.
In the catalytic-cracking process, the crude oil is cracked in the presence of a finely divided catalyst. This permits the refiner to produce many diverse hydrocarbons that can then be recombined by alkylation, isomerization, and catalytic reforming to produce high antiknock engine fuels and specialty chemicals. The production of these chemicals has given birth to the gigantic petrochemical industry, which turns out alcohols, detergents, synthetic rubber, glycerin, fertilizers, sulfur, solvents, and the feedstocks for the manufacture of drugs, nylon, plastics, paints, polyesters, food additives and supplements, explosives, dyes, and insulating materials. The petrochemical industry uses about 5 percent of the total supply of oil and gas in the U.S.
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 disciplines employed by exploration and 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 afford 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 wire line. Seismologists interpret sophisticated signals returning to the surface from sound waves that are propagated through the earth s crust. Geochemists 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, petrophysical and geological analysis of the reservoir, reserve estimation and specification of optimal development practices, or production control and surveillance. Again, 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.
The drilling engineer specifies and supervises the actual program by which a well will be bored into the earth, the kind of drilling mud to be used, the way in which the steel casing that isolates the productive strata from all other subsurface strata will be cemented, and how the productive strata will be exposed to the well bore. The facilities-engineering specialists specify and design the surface equipment that must be installed to support the production operation, the well-head pumps, the field measurement and collection of produced fluids and gas separation systems, the storage tankage, the dehydration system for removing water from the produced oil, and the facilities for enhanced recovery programs.
The petrophysical and geological engineer, after interpreting the data supplied by analysis of cores and by various logging devices, develops a description of the reservoir rock and its permeability, porosity, and continuity. The reservoir engineer then develops the plan for the number and location of the wells to be drilled into the reservoir, the rates of production that can be sustained for optimum recovery, and the need for supplementary recovery technology. The reservoir engineer also estimates the productivity and ultimate recovery (reserves) that can be achieved from the reservoir, in terms of time, operating costs, and value of the crude oil produced.
Finally, the production engineer monitors the performance of the wells. The engineer recommends and implements remedial tasks such as fracturing, acidizing, deepening, adjusting gas to oil and water to oil ratios, and any other measures that will improve the economic performance of the reservoir.
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 of petroleum 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 can be 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 the recovery 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 1970s.
Alternatives
In light of the reserves available and the dismal projections, it is apparent that alternative energy sources will be required to sustain the civilized societies of the world in the future. The options are indeed few, however, when the massive energy requirements of the industrial world come to be appreciated. Commercial oil shale recovery and the production of a synthetic crude oil have yet to be demonstrated successfully, and serious questions exist as to the competitiveness of production costs and production volumes that can be achieved by these potential new sources.
The various problems and potentials involved in such alternative sources as geothermal energy, solar energy, and nuclear energy are discussed in see Energy Supply, World. The only other 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. Adequate safeguards can perhaps be set on its use by modern engineering technology, with little increase in capital and operating costs.