Page 460 - Fundamentals of Enhanced Oil and Gas Recovery

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La Jolla, California. A comprehensive review of the early works is available in litera-
ture by Premuzic and Woodhead [86].
The starting point of MEOR field trials in former Soviet Union backs to the
1960s. Encouraged by this, four Eastern European countries of former
Czechoslovakia, Poland, Hungary, and Romania performed some field trials [31].For
example, in Romania, several MEOR field tests were performed between 1971 and
1982, reporting successful results [31,104]. Youssef et al. [6] mentioned the improve-
ment in the technology of MEOR as using mixture cultures adapted to the nutrients
and reservoir condition such as temperature and pressure and also incorporating larger
volumes of nutrients [105 114].
In 2003, Van Hamme et al. [19] stated that more than 400 MEOR field projects
have been done so far just in the United States. Based on Khire and Khan [43,115],
MEOR projects has been applied on over 400 wells in the same country. In addition,
this recovery method has been tested on more than 1000 wells in numerous oil fields
in China [32]. Based on Thomas [116], an estimated amount of 2.5 million oil barrels
per day were produced in 2007 using EOR method, of which the role of MEOR
was negligible. On the other hand, based on a report by Chinese Ministry of Land
and Resources (www.mlr.gov.cn), nearly 50 billion oil barrels in onshore Chinese oil
fields have the potential to be treated by MEOR [32]. Youssef et al. [6] specified that
the residual oil saturation in many MEOR field trials increased by 10% 340% for
2 8 years [78,92,99,101,106,108,117]. In recently performed reviews, Maudgalya
[23] in 2007 mentioned 407 field trials reported in literature [11,76,78,87,108 110,
114,351,392,408 410,702,763,766,780,800,803,849,888 904]. In the investigated
trials, among the different recovery mechanisms, the permeability profile modification
has been the most successful. A list of some MEOR field trials is presented in
Table 10.7.

10.14 ENZYME ENHANCED OIL RECOVERY

Incorporating the enzymes in petroleum industry was first suggested by Harris
and Mckay in 1998 [946] for:
1. Enzyme pretreatment of biopolymers to improve them;
2. Handling characteristics and gel breaking in drilling to disrupt filter cake
formation;
3. Desulfurization of hydrocarbons; and
4. Enzyme-based acid production for different purposes like formation damage treat-
ment and matrix acidizing of carbonate, etc.