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The Energy Factor, Part II
The E
TP
Model
Petroleum, and its products are produced for the energy that they contribute to the general economy. To determine the depletion status of the world's petroleum reserve it is necessary to determine the amount of energy remaining in that reserve that can be delivered to that economy. This can be accomplished by applying what science, and engineering have learned about energy over the last one-hundred and fifty years. The result is called the ETP model.

ETP is an acronym that stands for Total Production Energy. It is the total energy needed to extract, process, and distribute a unit of petroleum. It is a computed value derived from the solution of a thermodynamic equation: The Entropy Rate Balance Equation for Control Volumes. The ETP curve (green curve) is shown in the adjacent graph. The red points are the values generated by the computer program to which the curve is fit. The ETP curve is a logistic function like the accumulated production function. The green line labeled 140,000 BTU/gal is the energy content (exergy) of 35.7 API crude. It is the same value that was reported by the EIA for the five year total production of 101.16 Gb between 2000 and 2004. The red line labeled 99,400 BTU/gal is the energy remaining after the minimum theoretical amount of waste heat that must be generated is subtracted (see study for details). The distance between the ETP curve, and the 99,400 BTU/gal line is the amount of usable energy supplied per gallon to the general economy for any specific year. The distance from the ETP curve to the X axis is the amount of energy used to extract, process, and distribute one gallon of petroleum for any specific year.
The energy to produce petroleum, and it products is increasing. As shown on the graph in 1960 it required 8,600 BTU/gal to extract, process, and distribute a gallon of petroleum, and its products. By 2012 that had increased to 70,900 BTU/gal. By 2030 that will have increased again to 99,400 BTU/gal, at which point there will remain no energy from petroleum to be used by the general economy. These values represent average units, some barrels will fall below the 99,400 BTU/gal level, and some above. The increasing energy costs of producing petroleum is the result of increasing well depth, increasing viscosity, and most of all increasing water cut. In 1960 the average world water cut for conventional crude was 22.8%, by 2012 that had risen to 46.9% (see study for details).

As discussed in Part I, as the energy to extract petroleum increases by one BTU the energy delivered to the general economy declines by almost five. When the energy to extract a gallon of petroleum reaches 20,327 BTU/gal the energy remaining for the general economy falls to zero. Many of the substitutes now being used to replace conventional crude are already close to that value. It is the lower production energy of the remaining legacy fields of conventional crude that are providing the energy consumed by the general economy. As the energy to extract conventional crude increases, the energy available for consumption by the general economy will continue to decline. Petroleum depletion is an ongoing event!
In Part III of this series we will look at the historical price of petroleum in relation to the energy that has been required to produce it. The ETP model will again be used to demonstrate that association.
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