Reserve growth

It is well known that reseive estimates made early in the development of a field are often wi ong and that there s a 50 percent change in estimated ultimate recovery in many fields during the first ten years. In addition, the average field lifetime has been a decade longer than initially expected in the North Sea. If you believe in reserve growth, you would conclude that there will not be a petroleum crisis anytime soon. If, on the other hand, you believe that reserves have been overstated and you make negative revisions to reserve estimates, there rvill be a crisis soon. Current known petroleum reserves (proved + P50 probable) in the world are 1.44 trillion barrels of oil, 5,845 trillion cubic feet of gas, and 80 billion barrels of natural... 

Another common criticism of oil reserves statistics relates to backdating of reserves, as new discoveries and revisions of previous reserve calculations are often not distinguished. When oil companies replace earlier estimates of the reserves left in many fields with higher numbers, it is a common practice that those revisions are backdated to the year in which a company or country corrected an earlier estimate and not to the year in which the field was discovered first. This practice leads to distortions of statistics regarding new discoveries, as the reserve growth, resulting from new discoveries and revisions of earlier estimates, is biased towards the present and often generally interpreted as discovery rate (Campbell and Laherrere, 1998). 

This reserve growth is largely due to enhanced oil recovery. In 2004, EOR contributed with 1.8 million barrels per day to about 2% of world production, with more than a third coming from the US (Moritis, 2006). The injection of C02 as a means to increase oil production is discussed in more detail in the context of CCS in Chapter 6. The Oil Gas Journal (2006b) estimates that more than 500 Gb can be produced with EOR methods. Enhanced oil recovery methods are also incentivised by high oil prices. 

US Geological Survey (USGS) (2000) USGS World Petroleum Assessment 2000, New estimates of undiscovered oil and natural gas, including reserve growth, outside the United Sates. USGS. 

Fig. 1. Growth of wodd s reserves of conventional petroleum. To convert to bbl, multiply by 6.29.

All these polyesters are produced by bacteria in some stressed conditions in which they are deprived of some essential component for thek normal metabohc processes. Under normal conditions of balanced growth the bacteria utilizes any substrate for energy and growth, whereas under stressed conditions bacteria utilize any suitable substrate to produce polyesters as reserve material. When the bacteria can no longer subsist on the organic substrate as a result of depletion, they consume the reserve for energy and food for survival or upon removal of the stress, the reserve is consumed and normal activities resumed. This cycle is utilized to produce the polymers which are harvested at maximum cell yield. This process has been treated in more detail in a paper (71) on the mechanism of biosynthesis of poly(hydroxyaIkanoate)s. 

Biological effects and stimulation of plant growth induced by hydrogel additives are observed at doses which are often much lower than those obtained from purely physical evaluation. For example, it has been recently shown [13] that, according to various criteria of plant development, the SAH additives even at dosages of 50 to 140 kg ha-1 provide a productivity in sandy soils at the level obtainable by treatment with 20% (of the order of hundreds of tons per 1 ha) alluvial deposits. There seems to exist a mechanism allowing the plants to efficiently utilize small water reserves contained in the SAH particles. 

When applied to growth from the melt (despite our reservations in Sect. 3.2), P is normally assumed to take the form... 

The projection of future emissions of fossil fuel CO2 is subject to a number of uncertainties. The growth rate has already shown great variations and the reserves of fossil fuels are not... 

The majority of PH As biosynthesis is performed by various microorganisms, especially bacteria. They can produce PHAs from a number of substrates and accumulate in their cells as carbon source and energy reserve under imbalanced growth conditions such as nutrient limitation. Fig.7 shows PHA accumulated in their cells that are characterized by transmission electron microscopic (TEM) technique. 

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