Construccion De Ductos Para Trnasporte y Recoleccion Final.

4.4 Métodos en proceso experimental de aplicación en laboratorio y campo.

Microbial Enhanced Oil Recovery (MEOR)

1 Mechanisms of MEOR
The use of microorganisms and their metabolic products to enhance oil production involves the injection of selected microorganisms into the reservoir and the subsequent stimulation and transportation of their in-situ growth products in order that theirpresence will aid in further reduction of residual oil left in the reservoir after secondary recovery is exhausted. The MEOR is unlikely to replace conventional EOR methods, because MEOR itself has certain constraints (limitaciones). This unique process seems superior in many respects, however, because self-duplicating units, namely the bacteria cells, are injected into the reservoir and by theirin-situ multiplication they magnify their beneficial effects3. Some of the mechanisms proposed by which these microbial agents could stimulate oil release are shown in Table 1.
Table 1 Microbial products & their contribution to EOR4
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2. History of Microbial Enhanced Oil Recovery
First Stage: Initial (~1975)
In 1895, Miyoshi first reported the growth of a mould culture on n-alkanes5. In 1926,Bastin did the first extensive microbiological study describing the widespread presence of SRB in oil-producing wells6. At the same year, Beckman suggested that microorganisms could be used to release oil from porous media7. Later in 1946, as the most important founder of MEOR, ZoBell patented a process for the secondary recovery of petroleum, using anaerobic, hydrocarbon-utilizing,sulfate-reducing bacteria such as Desulfovibrio species in situ8. The first field test was carried out in the Lisbon field, Union County, AR in 19549. Kuznetsov et al. found that bacteria discovered in some oil reservoirs in the Soviet Union produced 2 gm of CO2 per day per ton of rock, in 196310.
Second Stage: Developmental (1975~1996)
From 1970s to late 1990s, MEOR research was boosted by the petroleumcrisis and later became a scientific substantiated EOR method. Many international meetings were periodically organized on the MEOR topic and proceedings volumes with the advances in the knowledge and practice of MEOR have been published. Several books on MEOR were also published4.
Third Stage: Rapid (1996~)
From late 1990s, modern biological methods began to be applied on the MEOR research, such asMolecular Ecological Technique of Microbes, Protoplast Fusant Technology, and Recombination DNA Technology11,1 2.
3. Current Status of MEOR
The research of MEOR has been done worldwide, and most of oil produce countries have applied this technology into oil fields for pilot tests. Recently this technology has been widely used in oilfields of China, such as Daqing, Shengli, Jilin, Dagang, Liaohe,Henan, Changqing, Xinjiang, and Qinghai.
4. Classification of MEOR
Mainly, MEOR is classified as surface MEOR and underground MEOR based on the place where microorganisms work. For surface MEOR, biosurfactand (Rhamnolipid13), biopolymer (xanthan gum14), and enzyme15 are produced in the surface facilities. These biological products are injected into the target place in the reservoirs as chemicalEOR methods. While, for underground MEOR, microorganisms, nutrients and/or other addictives are injected into the reservoir and let them sustain, grow, metabolize, and ferment underground.
Based on the source of microorganisms, underground MEOR is categorized into in-situ MEOR and indigenous MEOR. While according to procedures of processes, underground MEOR is sorted as:
• Cyclic MicrobialRecovery (Huff and Puff, Single Well Stimulation)
• Wax Removal and Paraffin Inhibition (Wellbore Cleanup)
• Microbial Flooding Recovery
• Selective Plugging Recovery
• Acidizing/Fracturing
a. Cyclic Microbial Recovery
A solution of microorganisms and nutrients is introduced into an oil reservoir during injection. The injector is then shut in for an incubation period...