The map I am going to link to at the end of this post, dated January 2012, shows all of the brine injection wells in Ohio, as of that date.
Forty-three of Ohio's eighty-eight counties host brine injection sites, with brine injected to different depths in different counties. Here, on this site, the counties are in alphabetical order for your convenience in finding your own county, or you can hit Ctrl+f and type the name of your county into the little search box that pops up, and it should take you right to it.
While the map is dated January 2012, it is possible it was only recently made available online, as I have done many, many, and very frequent Internet searches for this information and this is the first I have found anything.
The map is color-coded to show what level or depth the brine is injected to in the earth's crust. (Check the map's key for more details on that.)
Some of the dots are piled on top of one another, making it hard to see without zooming, but here is a basic rundown of how many injection wells can be found in each county. The counties with brine injection wells are highlighted to make it easier to spot them. The wells shown crossing county lines are not accurately represented here because I did not know which county gets to - or has to - claim each of those.
- Adams: None
- Allen: None
- Ashland: None
- Ashtabula: Twelve
- Athens: Seven (Three appear to overlap Vinton and Meigs county lines)
- Auglaize: One
- Belmont: Two
- Brown: None
- Butler: None
- Carroll: Four (two appear to overlap into Tuscarawas and Stark county lines)
- Champaign: None
- Clark: None
- Clermont: None
- Clinton: None
- Columbiana: Five (all of these are on the Stark and Mahoning county lines, making it hard to determine which county actually gets to claim them.
- Coshocton: Four (one is on the Knox county line)
- Crawford: None
- Cuyahoga: None
- Darke: None
- Defiance: None
- Delaware: One
- Erie: One
- Fairfield: None
- Fayette: None
- Franklin
- Fulton: One
- Gallia: Two
- Geauga: Four (two are on county line shared with Ashatabula County)
- Greene: None
- Guernsey: Three
- Hamilton: None
- Hancock: None
- Hardin: One (on county line shared with Marion and Wyandot)
- Harrison: None
- Henry: One
- Highland: None
- Hocking: Two
- Holmes: Five (one on Wayne county line)
- Huron: None
- Jackson: None
- Jefferson: One
- Knox: Five (one on Coshocton county line)
- Lake: Two (one on edge of Lake Erie)
- Lawrence: None
- Licking: Two
- Logan: None
- Lorain: One
- Lucas: None
- Madison: None
- Mahoning: Nine (six are on the Columbiana, Stark, and Trumbull county lines)
- Marion: None (But one is on county lines where Marion, Hardin, and Wyandot counties meet)
- Medina: One
- Meigs: Eleven (one is on the county line between Meigs, Athens, and Vinton)
- Mercer: None
- Miami: None
- Monroe: None
- Montgomery: None
- Morgan: Ten (two are on the border of Muskingum and Athens counties)
- Morrow: Thirteen
- Muskingum: Five (one is on the border of Morgan county)
- Noble: Four (two are together on the border of Washington county)
- Ottawa: None
- Paulding: None
- Perry: Three
- Pickaway: Seven
- Pike: None
- Portage: Eighteen (five are on the borders of Geauga and Trumbull Counties)
- Preble: None
- Putnam: None
- Richland: One
- Ross: None
- Sandusky: None
- Scioto: None
- Seneca: Two
- Shelby: None
- Stark: Seventeen (five are on the borders of Summit, Mahoning, and Carroll counties)
- Summit: One
- Trumbull: Nine (four are on the borders of Portage and Mahoning counties)
- Tuscarawas: Six (two are on the border of Carrol county.)
- Union: None
- Van Wert: None
- Vinton: Four (all on the border of Athens and Meigs counties)
- Warren: None
- Washington: Nine
- Wayne: Three (one on the border of Holmes)
- Williams: None
- Wood: One
- Wyandot: Two (one on the border of Hardin and Wyandot counties)