omponents extending between formation 5 and work station 1 and passing through marine conductor 8 and well bore 3) 11 Hoisting means supporting testing string 10 12 Derrick structure supporting hoisting means 11 13 Well head closure at upper end of marine conductor 8 14 Supply conduit for fluid operable to transmit fluids such as mud to interior 6 of well bore beneath blow- out preventers of insta