Microbial plugging of reservoirs by bacteria in waterflooding injection waters can cause poor injectivity and loss of oil productivity. Several types of bacteria like SRBs, iron bacteria, and slime forming bacteria have been found in injection waters and can cause plugging through processes like precipitation or biofilm formation. Studies show that live bacteria cause more plugging through microbial metabolites and polysaccharides than dead bacteria. Plugging is reduced by limiting nutrients for bacterial growth and using biocides. For successful microbial enhanced oil recovery, bacteria size and behaviors like extracellular polymer production and biofilm formation must be controlled.

1. Presented by
Susmit Chakraborty
Roll No. BT16D301
Indian Institute of Technology Madras
Microbial Plugging in Reservoirs And Its
Implications in Microbial EOR

2. Bacteria In Waterflooding Injection Waters
What is Microbial Plugging of Reservoirs?
Poor water quality results in plugging of injection well.
Loss of injectivity causes loss of oil productivity.
This problem also persists in polymer flooding, alkaline flooding, micellar flooding,
etc.
Presence of various microbes in 67% well-bore samples (Myers and Slabyj, 1962)

3. Bacteria In Waterflooding Injection Waters

4. Bacteria In Waterflooding Injection Waters
SRBs: cause plugging by precipitation of iron sulfide and calcite.
Iron bacteria: cause plugging by iron oxide precipitation.
Slime forming bacteria (SFB): causes plugging of sand packs and soils. < 10 SFB/ml
of injection water (Hensel et. al., 1981).
Pic. Courtesy: Wikipedia

5. Studies of Plugging by Dead Bacteria
Cells act as particles in the plugging.
Ratio of Pore throat-size (d1) to Particle diameter (d2): governs particulate plugging
(Gruesbeck and Collins, 1979)
d1/d2 ≥ 13 d1/d2 = 4-6 (log-jam effect)
d1/d2 ≤ 2.6
Pic. Courtesy: Gruesbeck and
Collins, 1979)

6. Studies of Plugging by Dead Bacteria
Rate of plugging depends on bacterial cell suspension density.
Plugging efficiency decreases from filamentous rod-shaped cells (1µm × 5 µm) to
small spherical cell aggregates (1 µm) to singly dispersed cells (1 µm × 2.5 µm).
Permeability never reduced to zero (90% for low permeable and 95% for high
permeable cores).
 Plugging effects of dead bacteria not so relevant compared to that of live bacteria.
Plugging by live and dead cells of
Pseudomonas sp. (Shaw, 1982)
SEM image of Pseudomonas dead cells causing
plugging in glass bead core (Shaw, 1982)

7. Studies of Plugging by Live Bacteria
Microbial metabolites, rather than microbes themselves clog pore throats.
Absence of organic nutrients and presence of biocides check microbial plugging.
Effect of adding sucrose solution to a percolating column
of silt-size sediments (McCalla, 1950)
Loss of permeability vs bacterial population in
sand pack column after 25 days of percolation
(Gupta et. al., 1962)

8. Studies of Plugging by Live Bacteria
Microbial growth and plugging occurred on front face of sand pack and is inhibited
further downstream.
Chemical precipitation insignificant compared to polysaccharides.
Microbial plugging in wellbore zone of injection well.
Viable bacteria disperse over significant volumes even under low pressure difference.
Correlation of total bacterial polysaccharide with permeability loss in sand column with
organic nutrients (Mitchell et. al., 1964)

9. Surface Growth & Biofilm Formation
Bacteria form biofilms ubiquitously.
Surface attachment through Glycocalyx sheath. It promotes growth, protects against
biocides and natural enemies.
Bacterial biofilm formation on an inert solid surface (Pic.
Courtesy: MEOR by Donaldson, et. al.)
SEM image of extensive polysaccharide
formation by live cells of Pseudomonas
sp. (Shaw, 1982)

10. Successful Injection MEOR
Bacterial size depends on formation pore throat size distribution.
Bacteria must not produce EPS or other polymers.
Bacteria should not form biofilms.
Bacteria should not generate gas bubbles in formation face.
Pic. Courtesy: Prof. J. Sangwai, DOE,
IIT Madras slides

11. Bibliography
Donaldson, E.C., Chilingarian ,G.V., Yen, T.F. Microbial Enhanced Oil Recovery,
Development of Petroleum Sciences, 22. Elsevier, 1989.
Jack, T.R., et. al., Microbial Plugging in Enhanced Oil Recovery. Chapter 7,
Microbial Enhanced Oil Recovery. 22, Elsevier, 1989.
Wikipedia web-links.
Class notes by Prof. J. Sangwai, IIT Madras.
Thank You