Got confused with the skin factor

[pet_spec]

Hello,

I need some clarification about skin factor.

As it is know, positive skin factor creates damage zone around the well-bore, and bottom-hole pressure drop is different from predicted one by Darcy's law i.e. is low. It seems that we have larger drawdown, and more production. Does this make sense? Isn't it the aim of the production engineers to get lower drawdown, to have more underbalance for fluid flow?

However, the productivity index, PI, will be low for lower bottom-hole pressure. Thus , lower quantity of oil will be produced per 1 psi drawdown.

Can anyone please help to establish connection between low PI due to positive skin factor and increased drawdown because of positive skin-factor? I got confused.

Thanks.

[vinomarky]

Think of formation damage related skin as a thin ring of poorer perm right at the wellbore, making it harder to suck the fluids out.

It means for a given rate you have to put more drawdown, or for a given drawdown you will have less rate.

PI is independant of BHP, it is expressed in terms of production rate /psi of drawdown.