An apparatus for controlling fluid pressure, useful in the production of hydrocarbons from underground reservoirs comprises at least one conical segment. A conical segment comprises: an inner conical cylinder with a central axis; an outer conical cylinder, outside of, and coaxial with, the inner conical cylinder; and a swirl chamber disposed between a conical outer surface of the inner conical cylinder and a conical inner surface of the outer conical cylinder. There is a fluid entrance through a wall of the outer conical cylinder of at least one conical segment at an upstream end of the apparatus for directing fluids into such conical segment's swirl chamber. There is also a fluid exit through a wall of the inner conical cylinder of at least one conical segment at a downstream end of the apparatus for directing fluids out of such conical segment's swirl chamber.