I found this interesting about multiple wells on one pad:http://www.csur.com/sites/default/files/Understanding_Well_Construction_final.pdf
---Companies can drill multiple wells from a single-pad location and extract the hydrocarbons from as much as 10 sq km.
Nice summary there, and people should check it out. There is a lot of information in that. I have worked as a wellsite geologist since 1979, and through most of the Bakken boom in ND. The most I have worked was four wells on a pad, but I have seen other companies put eight or more on one. One of the other benefits, is that by drilling parallel wellbores in opposite directions, the well pads line up and the access roads, pipeline easements, and traffic all tend to trend along lines, 2-4 miles apart, when topography and other considerations permit. This leaves large swaths of land in between the production 'strips' which are pretty much undisturbed, be that pasture, farmland, or undeveloped 'wild' land.
Another feature of the multiwell pad is that for the last few years, drilling rigs have been designed to 'walk' from wellbore to wellbore, removing the necessity to completely tear down and reassemble the rig for a move to the nest wellbore. The advantage is that (literally) weeks are saved (along with half a million to a million dollars) on rig moves, and more wells can be drilled by the same rig in less time.
Compared to individual drill sites for each well, a lot of money is saved between earthwork and drilling expenses, and the 'footprint' for the whole operation is far far smaller than it would have been for drillsites and the follow-on production sites for separated wells.