A ground detonation against dispersed mechanized troops is not especially useful. Say that 100% of the troops within 1000 meters are killed (and that is a very high estimate) and 50% in the range 1000-2000 meter. Outside that I doubt any troops inside armored vehicles would be affected.
In 1991 the Coalition had a lot of space to manuver in, GPS guidance and total air control. They spread out, partly to avoid any WMDs.
So a battalion is killed outright. Let say another battalion suffers 50% losses. That would be somewhere between 1 000-1 500 men. The military effect would be very small, but the political would be far bigger. It also depends om which country is the target - US, Britain, France, Saudi Arabia or someone else.
My guess is that UN Security Council demands that Iraq is occupied, de-nuked and that Saddam is dragged to Hague. The Coalition would probably agree, and I see no problem in invading Iraq.
But now the butterfilies starts. Would the occupation be a success - Saddam had not prepared any guerilla warfare campaign in 1991 as he did 2003. What would happen with radical islamism when an arab muslim were the first to use nukes against muslims, not Israel, US or the Soviets?
A good source for nukes is
http://nuclearsecrecy.com/nukemap/