A flow diverting conduit string (70, 76) for injecting fluid into or extracting fluid from a subterranean borehole in salt or a subterranean salt cavern, said conduit string comprising: an inner conduit string disposed within an outer conduit string, with an inner passageway in said inner conduit string and a first annular passageway between said inner and outer conduit strings; said conduit string being a flow diverting conduit string with at least one lateral opening (44, 64, 67, 90) in said inner or outer conduit string (2, 2A); said lateral opening communicating with at least one of said passageways (24, 25) and with said borehole or cavern, and flow control apparatus (22, 25A, 47) arranged to control flow of said fluid between or along said passageways (24, 25) to enable said flow-diverting conduit string to be used for storage and extraction of gases, hydrocarbon liquids, or combinations thereof, in and from said cavern and at least one of solution mining operations, subterranean hydrocarbon separation and dewatering operations; characterised in that said conduit string further comprises: a subsurface valve arrangement (78, 105) formed with said flow control apparatus for controlling flow of fluid stored in said cavern, wherein the flow control apparatus isolates opposing fluid flows within or about said subsurface valve arrangement for controlling fluid flows during solution mining operations, subterranean hydrocarbon separation and dewatering operations, and wherein said flow control apparatus is removable or replaceable from within said inner passageway to bring said subsurface valve arrangement into communication with said flow of fluid of said solution mining operations, subterranean hydrocarbon separation and dewatering operations. an inner conduit string disposed within an outer conduit string, with an inner passageway in said inner conduit string and a first annular passageway between said inner and outer conduit strings; said conduit string being a flow diverting conduit string with at least one lateral opening (44, 64, 67, 90) in said inner or outer conduit string (2, 2A); said lateral opening communicating with at least one of said passageways (24, 25) and with said borehole or cavern, and flow control apparatus (22, 25A, 47) arranged to control flow of said fluid between or along said passageways (24, 25) to enable said flow-diverting conduit string to be used for storage and extraction of gases, hydrocarbon liquids, or combinations thereof, in and from said cavern and at least one of solution mining operations, subterranean hydrocarbon separation and dewatering operations; characterised in that said conduit string further comprises: a subsurface valve arrangement (78, 105) formed with said flow control apparatus for controlling flow of fluid stored in said cavern, wherein the flow control apparatus isolates opposing fluid flows within or about said subsurface valve arrangement for controlling fluid flows during solution mining operations, subterranean hydrocarbon separation and dewatering operations, and wherein said flow control apparatus is removable or replaceable from within said inner passageway to bring said subsurface valve arrangement into communication with said flow of fluid of said solution mining operations, subterranean hydrocarbon separation and dewatering operations. a subsurface valve arrangement (78, 105) formed with said flow control apparatus for controlling flow of fluid stored in said cavern, wherein the flow control apparatus isolates opposing fluid flows within or about said subsurface valve arrangement for controlling fluid flows during solution mining operations, subterranean hydrocarbon separation and dewatering operations, and wherein said flow control apparatus is removable or replaceable from within said inner passageway to bring said subsurface valve arrangement into communication with said flow of fluid of said solution mining operations, subterranean hydrocarbon separation and dewatering operations.