I'm not sure if this is it or not, but the SOUTH CAROLINA HISTORICAL MAGAZINE Vol 60 No. 4 (Oct 1959)contained an article titled "Recollections of John Safford Stoney, Confederate Surgeon". Try the link or Google the title and it will come up. It seems to meet some of your criteria (surgeon, Benning's Brigade) but the whole article does not show free online unless you qualify for one of the access options. Would this be what you are looking for?

I saw this mention on the TOCWOC Civil War Blog: "Savas Beatie has a two-volume set on The Petersburg Campaign, taken from a series of unpublished battle studies written by Ed Bearss, edited by Bryce Suderow in the works. This has no publication date." Could you provide us with any addtional info?