ENHANCED OIL RECOVERY

During the initial stages of producing oil, or primary production, the oil is at least partly forced to the surface by natural forces such as expansion of natural gas contained above the oil in the underground reservoir. Primary production (which includes pumping) recovers only from 10 to 50% of the oil in place, and other methods must then be used to force it to the surface.

The most common is waterflooding or secondary production: Water is injected into the oil field through one set of wells to force the oil up another set of wells. At present, about 50% of all US crude oil production comes from secondary recovery.

Secondary methods will not work on oil too thick to flow easily. It must then be recovered from its reservoir and from all the nooks and crannies in it by tertiary methods or enhanced oil recovery. This includes all methods that provide the oil with greater viscosity, i.e., ability to flow easily. It can be done by heating the oil, or by injecting a "miscible agent" that dissolves the oil and results in a single oil like liquid with higher viscosity, or by chemicals that emulsify or dissolve the oil, or by even more exotic methods.

Heating the oil is accomplished by injecting hot water or steam (or both, and this again in a variety of schemes and schedules). In ''fireflooding,'' some of the oil is ignited to make the combustion gases heat the remaining oil and push it toward the recovery wells. Materials that will mix with oil are usually too expensive to make miscible processes profitable; an exception may be carbon dioxide, which is being tried in several projects. Chemical processes appear to be even more expensive, but no single method is optimal for all reservoirs.

Among the exotic processes perhaps the most interesting is one involving bacteria turning oil into detergent like materials that would then act much like the ones used in chemical flooding. There are such bacteria, at least in test tubes, but so far none have been found that would also withstand the temperature, pressure and chemical constitution of the environment inside an oil reservoir. Work with these bacteria is now in progress, but even in the absence of witch hunts on genetic engineering ("Mad scientists infecting oil wells!"), such strains could not be developed to the point of commercial feasibility before the end of the century.

Once again, the roots of the problem are not technological; with price controls keeping primary oil underground, there is not much hope for secondary, and still less for tertiary oil recovery. The OTA report recognizes that the amount available depends on price. Though it claims the amount is not as large as previous studies had indicated, it does estimate the reserves obtainable by enhanced recovery at present world oil prices ($14.32/ barrel) between 11 and 29 billion barrels (and up to 51 billion barrels at higher prices).

How much is 29 billion barrels? More than 10 years' worth of US oil imports at present levels. At prices the government is willing to pay to the sheiks of Saudi Arabia, but not to the producers of Texas and Louisiana.

"If we were to decontrol the price of oil, where would the new oil come from?" goes the standard rhetorical question by DoE spokesmen. They can find part of the answer in this report, stock no.05n 003 00503 4, $4.25 from Govt. Printing Office, Washington, DC 20402.