Page 115 - Enhanced Oil Recovery in Shale and Tight Reservoirs

102 Enhanced Oil Recovery in Shale and Tight Reservoirs

Figure 4.24 Corrected recovery factors from different operation schemes.

348 bbl/d condensate to 0.25 MMscf/d and 87 bbl/d, respectively. The
production decline might be caused by water-base-mud filtrates, completion
fluids, and condensate blanking. Well tests estimated permeability of 0.039
mD and a total skin of 0.68.
The well was treated by bull heading 1000 bbl methanol down the
tubing at a rate of 5e8 bbl/min. After the treatment, the well production
increased from 0.25 to 0.5 MMscf/d gas, and 87 to 157 bbl/d condensate.
Although the permeability was almost unchanged, the total skin improved
from 0.68 to 1.9, indicating wellbore damages were removed by the
methanol. This production rates increased in 2 for 4 months and 50% there-
after (Al-Anazi et al., 2005).

4.8 Surfactant treatment

The principle of using surfactants to treat condensate blocked wells is
wettability alteration of a strongly oil wet formation to a preferential gas wet
formation (Li and Firoozabadi, 2000). Application of a nonionic fluorinated
polymeric surfactant in sandstone cores has shown to increase both the gas
and condensate relative permeabilities by a factor of 2 to 3 (Kumar et al.,
2006). Their surfactant solution was prepared in a methanol-water mixture.
A fluorinated surfactant was prepared in a mixture of isopropanol and
propylene glycol (Bang et al., 2008) and in a 2-butoxyethanol-ethanol
mixture (Bang, 2007). When the surfactant treated sand-filled propped
fractures, relative permeability of gas was improved by the order of