From drilling to producing there maybe many companies working on the well. Land is usually owned by big oil producers (Shell,Exxon,BP, etc) while the drilling,

From drilling to producing there maybe many companies working on the well. Land is usually owned by big oil producers (Shell,Exxon,BP, etc) while the drilling, casing (protects the ground water), and hydraulic fracturing jobs may all be done by separate service companies. All in all, yes these barriers should hold and safety factors are taken into consideration. But when the service company doing the casing job recommends job A that will surely hold but the land holding company wants job B which is cheaper and might fail, who's at fault when it fails?