Summary
The present work is a part of a thorough and systematic laboratory study of
oil-in-water emulsion flow in porous media that we have undertaken recently to
investigate the mechanisms of oil-droplet retention and its consecutive effect
on permeability. One of our main objectives was to see how the in-depth
propagation of produced-water (PW) residual dilute emulsion could impair the
permeability during PW reinjection (PWRI). During this casework, we used
granular packs of sharp-edged silicon carbide grains and stable and dilute
dodecane-in-water emulsions. The flow experiments were performed under
well-controlled conditions, and we studied the effect of most of the relevant
parameters, including flow rate, salinity, droplet size, and permeability of
the porous medium.
A careful monitoring of the salinity and the jamming ratio (JR) allowed us
to consider and work separately on the two main mechanisms of droplet capture
(i.e., surface capture and straining capture). In a previous paper (Buret et
al. 2008), we reported on the effect of salinity and flow rate on emulsion flow
through porous media where the pore-size/droplet-size ratio (JR) was very high,
ensuring that only droplet capture on pore surface is operative. This paper
reports on the effect of salinity and JR on both mechanisms, with the main
focus being on the induced permeability impairment.
We demonstrated that surface capture could induce significant in-depth
permeability losses even at a high JR. The maximum reached permeability loss is
very sensitive to salinity and flow rate (shear-thinning effect). This maximum
is always lower than a limiting value dictated by the surface-coverage jamming
limit of random sequential adsorption (RSA) theory. This limiting value
increases while decreasing the JR, according to a simple formula extracted from
Poiseuille's law with a mean hydrodynamic thickness of the deposited layer
close to the droplet diameter (monolayer deposition). Regarding the straining
capture, we determined a critical JR of 7 for this mechanism to occur.
Preliminary results using only two JR values and one flow rate are presented.
Compared to surface capture, the results show that straining capture induces
more severe plugging with a lower rate of propagation. The lower the JR is, the
more severe the plugging is and the lower the propagation rate is. However,
more investigations are still required, notably using various JRs and flow
rates to characterize this important mechanism better.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
27 March 2009
- Meeting paper published:
27 May 2009
- Revised manuscript received:
26 August 2009
- Manuscript approved:
11 September 2009
- Published online:
3 March 2010
- Version of record:
17 June 2010
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