120 • Impacts of Applied Genetics — Micro-Organisms, Plants, and Animals 
as readily as water, but many of the reser- 
voirs contain oil as viscous as road tar. 
Miscible processes use injected chemicals 
that blend with the crude oil to form mix- 
tures that flow more readily. The chemi- 
cals used include alcohols, carbon dioxide, 
petroleum hydrocarbons such as propane 
and butane-propane mixtures, and petrole- 
um gases. A fluid such as water is generally 
used to push a “slug” of these chemicals 
through the reservoir to mix vvdth the 
crude oil and move it to the surface. 
• Chemicals are also used in alkaline flood- 
ing, polymer flooding, and combined sur- 
factant/polymer flooding. 
In alkaline flooding, sodium hydroxide, sodi- 
um carbonate, or other alkaline materials are 
used to enhance the flow of oil. Neither natural 
nor genetically engineered micro-organisms are 
considered useful in this process. 
Polymer flooding is a recent apparently suc- 
cessful method of recovery. It depends on the 
ability of certain chains of long molecules, 
known as polymers, to increase the viscosity of 
water. Instead of altering the characteristics of 
the crude oil, the aim is to make the injected 
water more capable of displacing it. 
In the combined surfactant/polymer flooding 
technique, a detergent-like material (surfactant) 
is used to loosen the oil from its surrounding 
rock, while water that contains a polymer to in- 
crease its viscosity is used to drive the oil from 
the reservoir. (See figure 27.) 
• Other EOR methods include many novel 
possibilities, such as the injection of live 
micro-organisms into a reservoir. These 
may produce any of the chemicals used in 
miscible and chemical processes, from sur- 
factants and polymers to carbon dioxide. 
One target for EOR is the half million strip- 
per wells (producing less than 10 barrels 
per day (bbl/d) in the United States. 
MICROBIAL PRODUCTION OF CHEMICALS 
USED IN EOR 
EOR methods that use chemicals tend to be 
expensive because of the cost of the chemicals. 
Nevertheless, potentially useful polymers were 
Figure 27. — Chemical Flooding Process 
Injection fluids Oil and water 
□ Drive water zone CD Surfactant slug zone 
IZD Water/polymer IH Oil and water zone 
zone 
SOURCE' Office of Technology Assessment, Enhanced Oil Recovery Potential 
i(i the United States (Washington, D C.: U S Government Printing Of- 
fice, January 1978). 
found in the early 1960’s and ha\’e sinct* heiMi 
responsible for the recovery of mort* than 2 
million bhl. Polymers such as polyacrylamide 
and xanthan gum can increase th(> \ iscosity ol 
water in concentrations as low as one part in a 
thousand. Xanthan gum is readily made in large 
quantities by micro-organisms. Different straiuh 
of Enterobacter aerogenes product' a w ide \ arie- 
ty of other polymers. A useful hiopolymei’— one 
formed by a biological process— might he de- 
signed specifically to improvt* oil recov cry. 
Xanthan gum, product'd by Xanlhomonas 
campestris and currently marketf'd by the kelco 
division of Merck &. Uo., Inc., is useful hut far 
from ideal for oil recovery. While it has ex- 
cellent viscous properties, it is also very expen- 
sive. Furthermore, unless it is exceptionally 
pure, it can plug reservoir pon*s, since the fluid 
often has to travel through hundicds of meters 
of fine pores. To avoid such plugging, the fluid 
must he filtered to remove bacterial dehi is be- 
fore it is injected. 
Nevertheless, micro-organisms can he -.e 
lected or genetically (‘iigineered to overcome 
many obvious difficulties.* With im|)roved 
properties, polysaccharides (polymeric -aigar-.! 
'A good organi.sm, loi' (■\ani|)li‘ miglii li.nr iln' i. ^ „ 
desired properties: ooo|)athogeoir to horn, ms pi, mis i, ■■■ ...il 
rapiti growlh on simple, cheap i .iw m.ilei'i.ds e.i-.e of .. p C: n 
from its |)rodii(Ts; limited detriment.d ellei I on le.r: .:, - 
plugging: easy disposal ofcells eg h\ pnidoi I i 1 1 lit- ,ilii n-, ■ 
