The Hubbert Curve
The Hubbert Curve is not a chart of an individual
field's production but rather a mathematical statistic formed from total
output of many fields. This page looks at the basic principles behind
M King Hubbert (1903-1989)
An individual field's production generally appears something like H1
- a gradual increase to maximum output, then a long plateau and a gradual
When you combine many fields together, placing a small number of large
fields near the beginning and a large number of small fields at the end,
as happens in oil exploration, the combined values produce something like
a bell curve. The examples below (H2 and H3) show how just four and eight
'wells' begin to approximate the shape of the Hubbert Curve.
Obviously the more wells you add, the smoother the curve. The US-48 had
around 240,000 producing wells in 2002 (ASPO).
It must be remembered that the Hubbert Curve is a theoretical curve that
is only likely to occur in long and stable areas (such as the US-48).
Most curves are distorted by wars, recessions, political interference,
etc, and are rarely symmetrical. But the most important principle of the
Hubbert Curve is not the shape but that fact that when approximately half
of the total oil is extracted, production will inevitably decline.
The Example of the US-48
most outstanding example of the Hubbert Curve predicting future oil production
was the initial forecast of the US-48 (which excludes Alaska and Hawaii)
by Hubbert himself in 1956.
Earlier predictions had simply divided the known reserves by production
(the R/P ratio) and they failed because they had not taken into account
future discoveries. M King Hubbert (1903-1989) was an American geophysicist
who realised that it was not when oil ran out that mattered but when it
began to decline. He made two educated guesses for how much oil would
be discovered and produced 150 and 200 Gb (ASPO's latest estimate
is 195 GB). After making plausible estimates of future production rates
for both guesses, he came up with the early 1970s for the more optimistic.
The actual peak year was 1970.
The curve for the US-48 (which can be seen in )
shows several features. There is no noticeable effect from major wars
such as the Second World War (1939-45) and the Vietnam War (1957-75).
There was also a slight increase in production in the early 1980s but
that did not last long or change the general trend. The US-48 curve shows
that events such as wars, recessions and oil prices do not dramatically
effect production (unlike consumption) unless they actually concern the
oil wells. If the Second World War had actually effected the US region
itself, with air attacks or invasions, oil production would also have
The clear proof of how the large oil wells are found first and the end
of the downslope results in many small wells is shown by comparing the
producing wells of the USA and Saudi Arabia (source: ASPO 2002).
USA and Saudi Arabia Well Situation
||Output per well (kb/day)
Applying the Curve to the World
example of the US-48 shows a fine example of the Hubbert Curve in action.
But other countries have examples which are not so neat. Iran's curve
shows a double peak and the world so far (right) looks more like the Himalayas.
At the moment, the world seems to be bumping along at the peak
but could this be the first of two or more? Could the world production
have another peak later on like Iran's?
The cause of both these effects are known. In Iran, there were wars and
revolutions which effected oil production. As we saw in the US-48, external
wars and revolutions do not alter production unless they bear on the wells
themselves. In Iran they did which is why there was a gap in the curve
and a second peak. As far as the world is concerned, if there had been
wars which effected the oil wells on the curve up (which would have meant
the USA, the North Sea, Saudi Arabia, etc) there would have been a drop
in production and a double curve. The drop in the curve in the 1980s was
due to recession which reduced demand, therefore lowering production (through
choice). When the peak occurs, production will fall through necessity
countries will not be able to raise production whether they want
to or not.
The example of world discovery also suggests that there is no more oil
waiting to be brought online for a second peak. Even if it was discovered
today, the time lag would not bring it online for a decade or so.
War may well effect oil production in the future. We have already seen
several wars in the Middle East over oil; that is likely to occur again
and again as supplies shorten. Since they will actively effect the wells,
production is likely to drop then, so adjusting the Curve. But these will
be valleys and peaks on the downslope. If you imagine the upslope
curve of the world above reversed, the valley might be where a war was
fought in Saudi Arabia. Once the war was finished, a small peak would
follow as production began again, but that peak would not be higher
than the main peak, the peak of highest production. World oil production
seems to be peaking now. There is no reason to assume that oil production
will rise higher in the future.
A mathematical explanation of the Hubbert Curve by Luís de Sousa
can be read on this