The graphs show that fluid density , increasable with the effective circulating fluid slurry density in excess of the subterranean strata pore pressure , must be maintained to prevent {TAIL ~ ingress} of {HEAD ~ unwanted subterranean substances} into said circulated fluid slurry and pressured caving of rock from the walls of the strata passageway 
The graphs show that fluid density , increasable with the effective circulating fluid slurry density in excess of the subterranean strata pore pressure , must be maintained to prevent { TAIL ~ ingress } of { HEAD ~ unwanted subterranean substances } into said circulated fluid slurry and pressured caving of rock from the walls of the strata passageway
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