US 4,299,260 A · Hydrocarbon production terminal

Abstract

An offshore oil production terminal system is described, of the type which includes a tall transfer structure that has a nonrotatable tower anchored to the sea floor and a rotatable portion that rotates with respect to the nonrotatable tower and is connected to a dedicated storage vessel. A fluid conduit of the system has a nonrotatable portion extending from the sea bed up alongside and through the tower to a fluid swivel at the top of the tower, the conduit also having a rotatable portion extending from the fluid swivel to the vessel. A choke located in the nonrotatable tower along the fluid conduit, decreases the high pressure of oil from the sea bed (e.g. 2,000 psi) to a moderate pressure (e.g. 200 psi) for passage through the fluid swivel, so that a moderate pressure fluid swivel can be utilized. In a system wherein the rotatable transfer structure portion is fixed to the vessel, the tower has a control deck at substantially the same level as the vessel deck and with a circular periphery. This facilitates entry of personnel onto the control system deck of the tower, and permits operation of a multitude of controls that are directly connected to various stationary valves and the like on the production trees at the sea bed without requiring rotational joints between the controls and the devices they operate. Power to produce pressured hydraulic fluid for controlling valves and the like, can be obtained by the passage of a powering fluid such as moderate pressure air (e.g. 200 psi) through a fluid swivel on top of the tower to an air-motor-hydraulic pump combination in the fixed tower, to produce high pressure hydraulic fluid (e.g. 3,000 psi) for control system operation.

Claims9

Dependent claims

In an offshore undersea hydrocarbon production terminal installation which includes a transfer structure with a portion that lies substantially at the sea surface and is anchored to the sea floor and connected to a floating storage vessel, and a fluid conduit which extends from the sea floor through the transfer structure to the vessel, to carry high pressure fluid from an oil well at the sea floor to the vessel, and wherein the vessel and a portion of the transfer structure must be allowed to rotate without limit about a vertical axis, the improvement wherein:

said transfer structure includes a nonrotatable frame anchored to the sea floor so it cannot rotate without limit about a vertical axis, and a rotatable frame which can rotate without limit about a vertical axis and which is connected to the vessel;
said fluid conduit includes a fluid swivel having a nonrotatable swivel portion substantially fixed to said nonrotatable frame and a rotatable swivel portion, and said fluid conduit also includes a rotating conduit portion connecting the rotatable swivel portion to the vessel;
and
said fluid conduit also includes a riser conduit portion extending from substantially the sea floor to said transfer structure, and a pressure reducing means mounted on said nonrotatable frame and connected between said riser conduit portion and said nonrotatable fluid swivel portion, for reducing the pressure of fluid that is delivered to the fluid swivel, to enable a moderate pressure fluid swivel to be used to carry initially high pressure fluid from the sea floor to the vessel;
said nonrotatable frame being positioned close enough to said vessel so a seaman stationed on said vessel can walk from said vessel to said frame to service said pressure reducing means and can then walk directly back to said vessel.

2 more elements

In an offshore production terminal for delivering hydrocarbons from at least one subsea well through a fluid conduit to a storage vessel, by way of a transfer structure that has a largely nonrotatable portion anchored to the sea floor so it does not rotate without limit about a vertical axis and a rotatable portion connected to the ship to rotate with the ship about a largely vertical axis, and wherein a plurality of underwater hydraulic valves are located along or near the fluid conduit and the valves are designed for individual control by high pressure hydraulic fluid delivered through hydraulic lines, the improvement comprising:

hydraulic fluid supply means having an outlet on said nonrotatable transfer structure portion, for supplying hydraulic fluid at high pressure;
and
a plurality of hydraulic controls located on said nonrotatable transfer structure portion, each control coupled to said hydraulic fluid supply means to receive high pressure hydraulic fluid, and each control also coupled to a corresponding underwater hydraulic valve to selectively supply high pressure fluid that operates the valve;
said hydraulic fluid supply means including a hydraulic pump device mounted on said nonrotatable portion of said transfer structure, a power source located on said vessel, and a power-carrying swivel unit having a rotatable portion coupled to said power source and a nonrotatable portion coupled to said hydraulic pump device to supply power to operate it.

1 more element

Dependencies are inferred from the claim text.

Hydrocarbon production terminal

Life of this patent

Hydrocarbon production terminal

Life of this patent

Abstract

Claims9