Prachi Asks PERM:
In hydraulic fracturing why it is preferable to use high capillary number in oil recovery system? Why it is preferable to decrease surface tension rather than increase in velocity?
Dr. Jonathan Bryan from PERM Answers:
Thanks for your question.
During hydraulic fracturing, the objective of the high pressure injection is to actually part the rock and get contact with the formation. Now beyond that, we need to consider that under this high pressure fluid state, there is POTENTIAL for some invasion into the formation. This isn’t necessarily what we want; we want good flow of reservoir oil back to the fractures, not a high saturation of fracture fluid blocking flow and reducing relative permeability to oil close to the fractures.
This is why surfactants are used: to drop IFT and capillary trapping in the region close to the fractures, so that oil from the high pressure formation can now flow easily into the fractures.
Dr. Jonathan Bryan