National Geographic : 1978 Nov
DOWELLDIVISIONOFDOWCHEMICALU.S .A.(ABOVEANDBELOW) 636 HYDRAULIC FRACTURING OF "TIGHT" SANDSTONE A blender truck ( draws water from storage tanks ® to mix with sand from a silo ® , a polymer, and other chemicals. Here directed from a remote control center ®, the mixture (blue arrows) is injected under great pressure by pump trucks ® deep into the perforated well casing to fracture surrounding rock ®. The polymerized liquid is later drawn off, leaving the sand in place to prop open the fracture ( . Gas (red arrows) then flows through the fracture to the well bore and into the pipeline for distribution ®.