Low-frequency elastic waves alter pore-scale colloid mobilization

Naturally occurring seismic events and artificially generated low-frequency elastic waves have been observed to alter the production rates of oil and water wells, sometimes increasing and sometimes decreasing production, and to influence the turbidity of water wells. TEe decreases in production are...

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Bibliographic Details
Published in:Langmuir 2009-01
Main Authors: Beckham, Richard Edward, Abdel-fattah, Amr I, Roberts, Peter M, Ibrahim, Reem, Tarimala, Sownitri
Format: Article
Language:English
Subjects:
BOROSILICATE GLASS
COLLOIDS
FLUCTUATIONS
FOULING
GEOSCIENCES
MICROSPHERES
OPTICAL MICROSCOPY
OSCILLATIONS
POLYSTYRENE
PRODUCTION
SEISMIC EVENTS
SOILS
STIMULATION
TURBIDITY
WATER WELLS
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Summary:Naturally occurring seismic events and artificially generated low-frequency elastic waves have been observed to alter the production rates of oil and water wells, sometimes increasing and sometimes decreasing production, and to influence the turbidity of water wells. TEe decreases in production are of particular concern - especially when artificially generated elastic waves are applied as a method for enhanced oil recovery. The exact conditions that result in a decrease in production remain unknown. While the underlying environment is certainly complex, the observed increase in water well turbidity after seismic events suggests the existence of a mechanism that can affect both the subsurface flow paths and mobilization of in-situ colloidal particles. This paper explores the macroscopic and microscopic effects of elastic wave stimulations on the release of colloidal particles and investigates the microscopic mechanism of particle release during stimulation. Experiments on a column packed with 1-mm borosilicate beads loaded with polystyrene microspheres demonstrate that low-frequency elastic wave stimulations enhance the mobilization of captured microspheres. Increasing the intensity of the stimulations increases the number of microspheres released and can also result in cyclical variations in effluent microsphere concentration during and after stimulations. Under a prolonged period of stimulation, the cyclical effluent variations coincided with fluctuations in the column pressure data. This behavior can be attributed to flow pathways fouling and/or rearrangements of the beads in the column. Optical microscopy observations of the beads during low frequency oscillations reveal that the individual beads rotate, thereby rubbing against each other and scraping off portions of the adsorbed microspheres. These results support the theory that mechanical interactions between soil grains are important mechanisms in flow path alteration and the mobilization of naturally occurring colloidal particles during elastic wave stimulation. These results also point to both continuous and discrete, en masse releases of colloidal particles.
ISSN:0743-7463
1520-5827