The Hubbert peak theory says that for any given geographical area, from an individual oil-producing region to the planet as a whole, the rate of petroleum production tends to follow a bell-shaped curve. It is one of the primary theories on peak oil.
Choosing a particular curve determines a point of maximum production based on discovery rates, production rates, and cumulative production. Early in the curve (pre-peak), the production rate increases due to the discovery rate and the addition of infrastructure. Late in the curve (post-peak), production declines because of resource depletion.
The Hubbert peak theory is based on the observation that the amount of oil under the ground in any region is finite; therefore, the rate of discovery, which initially increases quickly, must reach a maximum and then decline. In the US, oil extraction followed the discovery curve after a time lag of 32 to 35 years.Jean Laherrere, "Forecasting production from discovery", ASPO Lisbon May 19–20, 2005 The theory is named after American geophysicist M. King Hubbert, who created a method of modeling the production curve given an assumed ultimate recovery volume.
Hubbert's peak "Hubbert's peak" can refer to the peaking of production in a particular area, which has now been observed for many fields and regions.
Hubbert's peak was thought to have been achieved in the United States contiguous 48 states (that is, excluding Alaska and Hawaii) in the early 1970s. Oil extraction peaked at per day in 1970 and then declined over the subsequent 35 years in a pattern that closely followed the one predicted by Hubbert in the mid-1950s. However, beginning in the late 20th century, advances in extraction technology, particularly those that led to the extraction of tight oil and unconventional oil resulted in a large increase in U.S. oil production. Thus, establishing a pattern that deviated drastically from the model predicted by Hubbert for the contiguous 48-states as a whole. Production from wells utilizing these advanced extraction techniques exhibit a rate of decline far greater than traditional means. In November 2017 the United States once again surpassed the 10 million barrel mark for the first time since 1970.
Peak oil as a proper noun, or "Hubbert's peak" applied more generally, refers to a predicted event: the peak of the entire planet's oil production. After peak oil, according to the Hubbert Peak Theory, the rate of oil production on Earth would enter a terminal decline. Based on his theory, in a paperNuclear Energy and the Fossil Fuels, M.K. Hubbert, Presented before the Spring Meeting of the Southern District, American Petroleum Institute, Plaza Hotel, San Antonio, Texas, March 7–8–9, 1956 he presented to the American Petroleum Institute in 1956, Hubbert correctly predicted that production of oil from conventional sources would peak in the continental United States around 1965–1970. Hubbert further predicted a worldwide peak at "about half a century" from publication and approximately 12 gigabarrels (GB) a year in magnitude. In a 1976 TV interview Hubbert added that the actions of OPEC might flatten the global production curve but this would only delay the peak for perhaps 10 years. The development of new technologies has provided access to large quantities of unconventional resources, and the boost in production has largely discounted Hubbert's prediction.
Hubbert's theory
Hubbert curve
In 1956, Hubbert proposed that fossil fuel production in a given region over time would follow a roughly bell-shaped curve without giving a precise formula; he later used the Hubbert curve, the derivative of the logistic curve,Bartlett A.A 1999 ,"An Analysis of U.S. and World Oil Production Patterns Using Hubbert-Style Curves." Mathematical Geology.M. King Hubbert, 1962, "Energy Resources," National Academy of Sciences, Publication 1000-D, p. 57. for estimating future production using past observed discoveries.
Hubbert assumed that after fossil fuel reserves (oil reserves, coal reserves, and natural gas reserves) are discovered, production at first increases approximately exponentially, as more extraction commences and more efficient facilities are installed. At some point, a peak output is reached, and production begins declining until it approximates an exponential decline.
The Hubbert curve satisfies these constraints. Furthermore, it is symmetrical, with the peak of production reached when half of the fossil fuel that will ultimately be produced has been produced. It also has a single peak.
Given past oil discovery and production data, a Hubbert curve that attempts to approximate past discovery data may be constructed and used to provide estimates for future production. In particular, the date of peak oil production or the total amount of oil ultimately produced can be estimated that way. Cavallo defines the Hubbert curve used to predict the U.S. peak as the derivative of:
where max is the total resource available (ultimate recovery of crude oil), the cumulative production, and and are constants. The year of maximum annual production (peak) is:
so now the cumulative production reaches the half of the total available resource:
The Hubbert equation assumes that oil production is symmetrical about the peak. Others have used similar but non-symmetrical equations which may provide better a fit to empirical production data.
Use of multiple curves
The sum of multiple Hubbert curves, a technique not developed by Hubbert himself, may be used in order to model more complicated real life scenarios. When new production methods, namely hydraulic fracturing, were pioneered on the previously unproductive oil-bearing Shale formations, the sudden, dramatic increase in production necessitated a distinct curve. Advances in technologies such as these are limited, but when a paradigm shifting idea impacts production and causes a need for a new curve to be added to the old curve, or the entire curve to be reworked. It should be noted, & it is well documented, that production from shale wells are unlike that of traditional well. A traditional oil well's rate of decline is shallow, & exhibits a slow, predictable rate of decline as the reservoir is drawn down (Drinking of Milkshake). Whereas production from shale wells, assuming successful fracturing, will see its peak production at the moment the well is brought in, with a drastic rate of decline shortly thereafter. However, one revolutionary aspect of these types of production methods are the ability to refracture the well. Production may be brought back up, to near peak levels with a reapplication of the fracturing technology to the subject formation. Once again releasing the hydrocarbons trapped tightly within the shale & allowing them to be drawn to the surface. This process allows the for an outward manipulation of the curve, simply by purposefully neglecting to rework the well until the operator's desired market conditions are present.
Reliability
Crude oil
Hubbert, in his 1956 paper, presented two scenarios for US crude oil production: most likely estimate: a logistic curve with a logistic growth rate equal to 6%, an ultimate resource equal to 150 Giga-barrels (Gb) and a peak in 1965. The size of the ultimate resource was taken from a synthesis of estimates by well-known oil geologists and the US Geological Survey, which Hubbert judged to be the most likely case. upper-bound estimate: a logistic curve with a logistic growth rate equal to 6% and ultimate resource equal to 200 Giga-barrels and a peak in 1970. Hubbert's upper-bound estimate, which he regarded as optimistic, accurately predicted that US oil production would peak in 1970, although the actual peak was 17% higher than Hubbert's curve. Production declined, as Hubbert had predicted, and stayed within 10 percent of Hubbert's predicted value from 1974 through 1994; since then, actual production has been significantly greater than the Hubbert curve. The development of new technologies has provided access to large quantities of unconventional resources, and the boost of production has largely discounted Hubbert's prediction.
Hubbert's 1956 production curves depended on geological estimates of ultimate recoverable oil resources, but he was dissatisfied by the uncertainty this introduced, given the various estimates ranging from 110 billion to 590 billion barrels for the US. Starting in his 1962 publication, he made his calculations, including that of ultimate recovery, based only on mathematical analysis of production rates, proved reserves, and new discoveries, independent of any geological estimates of future discoveries. He concluded that the ultimate recoverable oil resource of the contiguous 48 states was 170 billion barrels, with a production peak in 1966 or 1967. He considered that because his model incorporated past technical advances, that any future advances would occur at the same rate, and were also incorporated.M. King Hubbert, 1962, "Energy Resources," National Academy of Sciences, Publication 1000-D, p. 60. Hubbert continued to defend his calculation of 170 billion barrels in his publications of 1965 and 1967, although by 1967 he had moved the peak forward slightly, to 1968 or 1969.
A post-hoc analysis of peaked oil wells, fields, regions and nations found that Hubbert's model was the "most widely useful" (providing the best fit to the data), though many areas studied had a sharper "peak" than predicted.
A 2007 study of oil depletion by the UK Energy Research Centre pointed out that there is no theoretical and no robust practical reason to assume that oil production will follow a logistic curve. Neither is there any reason to assume that the peak will occur when half the ultimate recoverable resource has been produced; and in fact, empirical evidence appears to contradict this idea. An analysis of a 55 post-peak countries found that the average peak was at 25 percent of the ultimate recovery.Steve Sorrell and others, Global Oil Depletion, UK Energy Research Centre, .
Natural gas
Hubbert also predicted that natural gas production would follow a logistic curve similar to that of oil. The graph shows actual gas production in blue compared to his predicted gas production for the United States in red, published in 1962.M. King Hubbert, 1962, "Energy Resources," National Academy of Sciences, Publication 1000-D, pp. 81–83.
Economics
Energy return on energy investment The ratio of energy extracted to the energy expended in the process is often referred to as the Energy Return on Energy Investment (EROI or EROEI). Should the EROEI drops to one, or equivalently the Net energy gain falls to zero, the oil production is no longer a net energy source.
There is a difference between a barrel of oil, which is a measure of oil, and a barrel of oil equivalent (BOE), which is a measure of energy. Many sources of energy, such as fission, solar, wind, and coal, are not subject to the same near-term supply restrictions that oil is. Accordingly, even an oil source with an EROEI of 0.5 can be usefully exploited if the energy required to produce that oil comes from a cheap and plentiful energy source. Availability of cheap, but hard to transport, natural gas in some oil fields has led to using natural gas to fuel enhanced oil recovery. Similarly, natural gas in huge amounts is used to power most Athabasca tar sands plants. Cheap natural gas has also led to ethanol fuel produced with a net EROEI of less than 1, although figures in this area are controversial because methods to measure EROEI are in debate.