Uykumun derin mi derin kuyusunda Elif’in sesi yankılandı

What could "mi" mean here, is it the one for questioning?

And if you please translate the sentence for me..

Sagol

mi doesn´t make a question here. Between repeated adjectives it intensifies their meaning, for instance:

                     İhtiyar zengin mi zengin. ´The old man is really rich.´

My Try for the meaning:

                      Elif´s voice resounded with echoes in the deep deep well of my sleep.

Thanks really...

It´s my first time that I come across another meaning of mi

 So does have the same meaning of "O kadar ..adj.. ki"?

What does "kuyru" mean here?

kuyu means ´well, pit´ and there are some suffixes attached to it:

                      kuyu|su|n|da = stem + POSS sg 3rd + pronominal -n- + LOC

I wish a native would explain the mi thing better. I have seen it in the intensifying function not only between adjectives but between verbs (gitti mi gitti) and adverbs (hiç mi hiç), too.