Workover in heavy oils, well performance reduction
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Published on 04-16-2011 11:30 PM
Hi everyone,
On some Canadian fields (heavy oil) it was observed that well performance decreased after workovers, whereas one would expect reverse results.
Any expatiations why?
Can anyone advise reading material or field experience on heavy/ highly viscous oil workovers?
Thanks for help.
Originally Posted by
Land_Mark
Many possible reasons,
Including;
1. Heavy oils with asphaltene content - certain workover fluids with certain ionic salts of metals may cause asphaltenes to become unstable and drop out of the stream and become deposited.
2. Alteration of relative permeability of oil due to excessive completion fluid leakage into formation, thereby increasing the saturation of water in the near wellbore region and decreasing the rel. perm to oil.
3. Excessive near wellbore cooling or that the workover fluid was hot water which entered the formation but was allowed to cool, causing a zone of wax precipitation in the near wellbore region.
4. Any other problems related to deposition of impurities in heavy crude oil.
5. Possibly need to refine workover strategy to properly cleanout the wellbore and wash perforations from time to time.
Markus L.
.
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