plugs, page-9

GiddyYup, I'm certainly not an expert but I can give you my take on the procedure.

They isolate an area in the well, say about 100 feet or so, and then they pressure it up with enough pressure to open up the cracks enough to force the slurry into them. This entire area has the same pressure and the sand slurry will flow to any area it can with lower pressure. After the pressure is released, the sand props open the cracks and allows fluid to pass to the well bore. Hope this is helpful - ELL