There's an article in "Sokar" magazine No.9 which is a German language journal of Pyramid studies. The article deals just with the Well Shaft and has lots of nice photos and diagrams. Unfortunately my German is non existent so it's a bit of a struggle but you might be interested in the "Abstract" which prefaces the article:

"The article deals with the function and the building history of the extensive constructed service shaft between the Grand Gallery and the Descending Corridor in the Cheops Pyramid. In the first phase of construction the shaft served as ventilation of the Subterranean Chamber. After the extension to the Grand Gallery the shaft apparently served as exit from the Upper Chambers after blocking the Ascending Corridor. The result of the research of different sections is that the shaft wasn't built in one connected construction plan." [Der Serviceschacht der Cheops-Pyramide, Sokar No 9, 2004].

Jon

www.egyptarchive.co.uk