Petroleum, literally rock oil from the Latin petra and oleum, has been a known and utilized natural resource for millennia. Only in the last century has it become the linchpin of the energy intensive industrialization of the modern world, the fuel on which our affluent lifestyle depends. It is a finite resource and it will eventually run out. The degree to which the inexorable depletion of petroleum is taken into consideration as a planned obsolescence will define the future as either a conflict over increasingly scarce resources or a gradual conversion to alternatives. The need to understand the nature of petroleum is necessary for an educated electorate to make informed decisions about the future. The geologic provenance of petroleum, the history of its exploitation, the extent of petroleum reserves, and the implications of its continued use are all aspects of this understanding.
The provenance of petroleum is subject to some speculation due to the complex variance of its composition and to the anomalous geology of its deposition. Unlike coal, whose origins are universally ascribed to the long term deposition of terrestrial phytomass during the Carboniferous Era, petroleum is thought to have its origins in the decomposition of marine organisms. This assertion is supported by geology, chemistry and physics. Petroleum deposits are geologically associated with sedimentary rock strata, those formed from the deposition of sediments in marine basins; conversely, igneous and metamorphic formations are virtually devoid of petroleum. Petroleum has complex hydrocarbon chemical constituents called porphyrins that are associated with the respiratory pigments (green chlorophyll and red hemin) of plants and animals and it has the isotopic carbon ratio (C13/C12) indicative of lipids, the fat, oil and wax constituents of both plant (mostly oil) and animal (mostly fat) living cells. Recently deposited marine sediments have similar hydrocarbon compositions as those found in ancient petroleum deposits. This would confirm James Hutton’s first geologic principle known as uniformitarianism: the present is the key to the past. That is to say that currently observable geologic marine deposition processes produce a similar chemical result as that found in the historic geologic record.
There is a theory that was advanced in Russia in the mid-20th Century based on the contention that petroleum originated from primordial carbon from deep within the earth’s core. The so-called abiogenic or non-organic theory is not considered plausible by geologists and earth scientists owing to the biogenic indicators that contradict it. The preponderance of the evidence is that petroleum is the end result of the demise and deposition of single-celled plants such as diatoms, algae and animal zooplankton such as foraminifera in marine sediments under anoxic (zero oxygen) conditions. The necessity of the anoxic environment predicated on the nature of bacterial action during the death and decay of petroleum’s organic precursors. Aerobic bacteria inhabit oxygen rich environments and rapidly decompose and destroy organic matter. Anaerobic bacteria exist in an oxygen free (anoxic) and maintain a reducing environment that is necessary for the accumulation of organic material. The postulated habitat is a marine basin at the bottom of a Precambrian or Paleozoic Era inland sea that spawned large volumes of the requisite single celled plants and animals that lived, died, and were then buried by fine-grained sediments inherent to these topologies. Based on the evidence afforded by the similarities between the C13/C12 ratio of petroleum and lipids, it is likely that water insoluble fats and fatty acids of the plants and animals are petroleum’s building blocks.
The deposition of dead marine organisms does not produce petroleum directly, but rather kerogen, a complex mixture of organic chemical compounds, the so-called “source rock” of geologic petroleum processing. Kerogen is from the Greek keros which means wax, a reference to its organic lipid origins. The kerogen must first be buried by sediment to protect the organic material from dissolution and consumption by aquatic bottom feeders and then buried by successive sedimentation. Over geologic time as the kerogen stratification areas are more deeply buried and subject to concomitant subsidence, the higher pressure caused by the buildup of overlying layers and the higher temperatures of deeper depths combine to convert the kerogen to petroleum. The process is known as diagenesis and occurs naturally in the temperature range of 60°C to 120°C, the “oil window.” At this point in the process, the kerogen – cum – petroleum admixture is still distributed over a wide geographic area in a relatively thin layer. Porous rock such as sandstone is necessary for the accumulation of sufficient quantities of the more fluid petroleum to percolate into reservoirs, water acting as the displacement vehicle. This is called primary migration. The accumulation of vast quantities of the now liquid petroleum into coherent reservoirs is dependent upon what is known as secondary migration; the hydrodynamic conveyance of the petroleum through porous rock is arrested by an impervious barrier rock that forms a trap repository. It is these reservoirs of migrated and collected petroleum that comprise the vast oil fields that provide the primary fuel resource of the world’s economy.
The process of petroleum formation into coherent reservoirs is thus a complex process that requires four sequenced events: the creation of source rock from expired marine organisms, heat-induced diagenesis, hydrologic percolation of the now fluidized petroleum and finally its coalescence into a coherent oil field under a trap rock. When kerogen is formed but is never processed by geothermal heating, oil shale results. Both of these terms are misnomers, since the kerogen is not oil but a petroleum progenitor and the rock formation in which it is deposited is not shale which is a specific clay sedimentary rock but a more variegated mixture of clay, sand and limestone called marl. The world’s largest oil shale deposits are the Green River Formation underlying parts of Colorado, Wyoming and Utah. When the diagenetic process has been completed such that petroleum is formed but there is no secondary migration for its coalescence, oil sands or tar sands result. Oil sands is descriptively appropriate since it consists of sand or sandstone cemented together with an asphaltic residue of petroleum called bitumen. Tar sands is a term that was used in the 19th and early 20th centuries due to the resemblance of oil sands to the then common coal based tars. The Athabasca Tar Sands of Alberta Canada and the heavy oil of the Orinoco valley in Venezuela are the world’s two predominant sites of oil sand bitumen deposits. Oil shales and oil sands, known collectively as non-conventional oils, have become increasingly important in the last twenty years due to the decreasing reserves of conventional reservoir fluid petroleum sources.
The use of petroleum by man extends to prehistory; the Sumerians, Babylonians and Assyrians are known to have used seepages in the Mesopotamian region 5,000 years ago. The Dead Sea was once called Lake Asphaltites which is considered to be the etymological root of the word asphalt, as petroleum washed up on its shores from submerged sources. Due to the dearth of timber and natural stone resources in the Tigris and Euphrates river basins of Mesopotamia (literally Greek for ‘between the rivers’), the petroleum asphalt was mixed with fiber and sand to make a construction material for bricks and levees. It may well be that the “cradle of civilization” was in part engendered by the availability of petroleum seepages. The use of petroleum from seepages eventually extended to ship caulking, road building, waterproofing, paints and, when ignited, as an “eternal flame” for religious shrines. In the 1st Century, the Persians discovered that petroleum could be distilled to produce a functional illuminant. The Iberian advances of the Moslems in the 7th and 8th Centuries brought the distillation of petroleum to Spain from which it spread to Western Europe. Seepages were discovered in the New World in locations ranging from Trinidad to Pennsylvania, where the Native Americans purportedly used them for medicinal purposes. When the whale oil that originally served the purpose of urban illumination in North America became increasingly scarce, the need for an alternative ultimately sparked the completion of the first well drilled for oil in the United States by Colonel Edwin L. Drake at Oil Creek, Pennsylvania on August 27, 1859.
The modern age of petroleum began on January 10, 1901 near Beaumont Texas at a place called Spindletop, a small mound created by the upward movement of a subterranean saline deposit called a salt dome. Geologically, East Texas had originally been an inland sea in which the marine organisms that formed the oil grew and died. As the sea receded, a two hundred foot salt deposit formed on top of the nascent kerogen which served as containment for the formation of petroleum. The gradual buildup of pressure from the blocked oil and gas caused the salt layer to buckle, forming Spindletop, and trapping a vast reservoir of petroleum beneath a one thousand foot layer of impervious limestone. Al and Curt Hammil employed the new technology of an engine driven rotary drill that replaced the percussion drilling technology of Drake’s day to drive a shaft 1,100 feet through the limestone to create the first “gusher.” Before Spindletop, oil wells only produced about one hundred barrels a day. The one hundred thousand barrels of oil a day pumped from Spindletop was more than all of the other wells operating throughout the world at that time. Subsequent major discoveries in Venezuela, Romania, Baku, Azerbaijan, and Sumatra, Indonesia established the potential of oil to serve the world’s energy needs. In 1908, the Masjid-e-Suleiman well was drilled in Iran, the first oil from the Middle East.
Petroleum consists mostly of hydrogen (11%-15%) and carbon (83%-87%). The hydrogen and carbon combine into a wide variety of chemical compounds called hydrocarbons that fall into three homologous (structurally similar) groupings or series: alkanes or paraffins, cycloalkanes or naphthenes and arenes or aromatics. The alkanes are classified by their covalent bonding according to the formula CnH2n+2 and include methane (CH4), the primary constituent of natural gas in addition to the larger molecules that are liquids at room temperature but boil between 100°F and 400°F. These liquid alkanes range from pentane (C5H12) and octane (C8H18), which are the primary constituents of gasoline to sequentially larger compounds that are the constituents of the thicker and denser distillate fuel oils (including diesel), kerosene, and lubricating oil. Cycloalkanes have the formula CnH2n and make up the bulk of most petroleums. They are broken down by the refining process into the lighter, liquid compounds; the residue from this processing is used in the production of asphalt. The aromatics are characterized by the ring-shaped benzene molecule C6H6 and are the least important of the primary petroleum compounds, the name corresponds to the fact that many of these compounds have a characteristic sweet, “aromatic” smell. Petroleum is measured in barrels – a barrel (abbreviated bbl) is 42 gallons, an anomalous unit thought to have originated in Pennsylvania where dubious buyers demanded a standard; the producers settled on adding 2 gallons to the standard 40 gallon whiskey barrel, the extra margin offered as an added incentive – like the 13 units in a baker’s dozen. A 42 gallon barrel of oil is refined into many derivative products including approximately 19 gallons of gasoline, 9 gallons of distillate fuel oil (including diesel), 4 gallons of jet fuel, 1.3 gallons of asphalt and 1.3 gallons of feedstock for things like plastics. Petroleum has earned the sobriquet “Black Gold.”
The term “peak oil” is used to define the point in time at which half of the world’s oil is pumped out of the ground and half remains. It was popularized by M. King Hubbert who predicted in 1956 that the United States output of oil would reach a peak in 1971, which it did. In that the world’s recoverable petroleum resources are finite, it is inevitable that there will be a peak in global oil, after which a gradual rise in prices will indicate a decline in availability. The question of when peak oil will occur will have a different answer according to the nature of the assumptions. In essence, peak oil timing is a simple matter of comparing known reserves of petroleum to the annual rate of consumption of petroleum. Complications arise when one considers the variability inherent in the estimation of known reserves, potential discoveries of future new oil reserves and the vicissitudes of global economics and demographics that define the rate of oil consumption over time. If one takes a snapshot of current estimates, there are about 1.2 trillion barrels of known petroleum reserves which is being consumed at the rate of about 80 million barrels a day. If the consumption rates were to stay constant and the reserves prove exact, then one half of the oil will have been consumed in about 20 years, which means peak oil in 2030 or so.
The estimation of oil reserves is fraught with inconsistencies since there are no universally established international standards. It is as much a qualitative art as a quantitative science. It may involve the economics of recovery as one of its parameters since oil that is too expensive to extract is not really available – unless the price goes up. There is even a lack of agreement as to the definition of reserves; a dichotomy exists between proven reserves which are known and the more nebulous combination of probable reserves (50% likelihood) and possible reserves (10% likelihood). Reserves are not static, as new oil fields have been and are continuing to be discovered at a rate that has historically outpaced consumption – a relationship that cannot be sustained indefinitely. Petroleum reserves were estimated at 85 billion barrels in 1950, 715 billion barrels in 1974. The estimate has been abouve1 trillion barrels since the mid 1990’s and currently stands at about 1.3 trillion barrels. The growth of oil reserves was the result of several enabling technologies that revolutionized petroleum extraction science and engineering. Seismic images used in conjunction with advanced computer three dimensional graphics have provided detailed maps of underground geologic formations. Years of experience in oil field exploration have provided the knowledge base for the use of the enhanced underground images to identify those that have promise. Improved materials and engineering of drills and drill components have made drilling to depths in excess of ten miles possible with the added capability of moving horizontally from any vertical penetration with sensors that can detect the presence of petroleum. The upshot of these improved technologies is that drilling can now occur in virtually any environment from the frozen tundra of Siberia to the deep waters of the North Sea. A secondary factor is that the new seismology and drilling techniques can be used to locate additional pockets of petroleum in existing oil fields, raising the recovery rate from about 30 percent to over 80 percent. The roseate view adds 2 trillion barrels of ultimately recoverable reserves and an (very rough) estimate of 2 trillion barrels of unconventional oil reserves to the 1.2 trillion barrels of known conventional oil reserves with a slow growth in demand to yield a turning point somewhere around mid-century. However, none argue that it will never end. However, like the Gadarene swine, we run headlong into the future and hope for the best.
The debate about the ability of earth’s resources to support the human population has been subject to the vicissitudes of public interest that mirror world economic and social conditions. Thomas Malthus is most famously known for his predictions of population growth in his 1798 “First Essay on Population” in which he opined that ” … the power of population is indefinitely greater than the power of earth to produce subsistence for man. Population, when unchecked, increases in a geometrical ratio. Subsistence increases in an arithmetical ratio. A slight acquaintance with numbers will shew (sic) the immensity of the first power in comparison to the second.” The Malthusian Principle that population would outpace the food supply without natural restrictions such as war, famine, pestilence or enlightened moral restraint was invalidated by the advent of fossil fuel energy, largely unknown in his time. While coal utilization offered heat energy for early steam engines to power nascent industry, it did not substantially impact agriculture; malnutrition was not uncommon in the 19th Century. The widespread availability of petroleum and the conversion of its chemical energy to mechanical work in the internal combustion engine revolutionized the human enterprise in the 20th Century. By the 1950’s, the petroleum fueled population had grown to the extent that the warnings of Malthus were again manifest; culminating with the publication of “The Limits of Growth” in 1972 and the environmental tocsin sounded by Paul Ehrlich in “The Population Bomb” – the recurrent theme being that the food supply, health and nature itself were threatened by the burgeoning population. After the Arab oil embargo, the rise in petroleum prices triggered global exploration that led to the discovery of new fields. Concomitant technological advances in petroleum extraction and agricultural productivity driven by growth oriented economic market forces have defined the last four decades with the Panglossian notion that there are no limits to growth. There are.
Peak oil is the limit to growth, as petroleum is the lifeblood of the agriculture business. Diesel powered farm machines are used in every aspect of food production, from plowing the fields to reaping the harvest, which is then processed in factories and packaged to be trucked to the local supermarket, from up to 2500 miles away. It is estimated that it takes 10 calories of fuel to make 1 calorie of food and that 19 percent of all energy use in the United States is devoted to food production and distribution. The use of fossil fuels, primarily petroleum, is estimated to provide the equivalent energy of having over 30 human slaves supporting every American. It is ironic that the Drake’s Pennsylvania oil field was drilled in the in the same year and not too far from the site of John Brown raided Harper’s Ferry that marked the beginning of the end of the institution of slavery, the erstwhile source of cheap energy in the New World. The challenge for the world’s population is to find alternatives to what will surely be a dystopia with wars over dwindling petroleum reserves wreaking a havoc that will shake the foundations of civilization. The challenge is not to find more oil or to process more oil sand or oil shale but to find something else – before it is too late.