Offshore fluid transfer systems and methods

A system for transferring fluids from a free-standing riser to a surface vessel, the system comprising;

• a first valve assembly including a first valve spool having an upper end, a lower end opposite the upper end, a flow bore extending between the upper end and the lower end, and a first isolation valve configured to control the flow of fluids through the flow bore of the first valve spool, wherein the flow bore of the first valve spool has an outlet at the upper end configured to supply fluids to the surface vessel and an inlet at the lower end;
• a second valve assembly releasably coupled to the first valve assembly with a hydraulically actuated connector, wherein the second valve assembly includes a second valve spool having an upper end, a lower end opposite the upper end, a flow bore extending between the upper end and the lower end, and a second isolation valve configured to control the flow of fluids through the flow bore of the second valve spool, wherein the flow bore of the second valve spool has an outlet at the upper end and an inlet at the lower end configured to receive fluids from the free-standing riser;
• a deployment/retrieval rigging coupled to the first valve assembly and configured to suspend the first valve assembly and the second valve assembly from the surface vessel;
• wherein the flow bore of the second valve spool is in fluid communication with the flow bore of the first valve spool;
• wherein each isolation valve has an open position allowing fluid flow therethrough and a closed position restricting fluid flow therethrough, wherein each isolation valve is biased to the closed position;
• wherein the first valve assembly includes a first hydraulic actuator coupled to the first valve spool and configured to transition the first isolation valve to the open position;
• wherein the second valve assembly includes a second hydraulic actuator coupled to the second valve spool and configured to transition the second isolation valve to the open position;
• and
• a hydraulic line severing system configured to sever or more hydraulic lines connected to the second hydraulic actuator upon disconnection of the upper valve assembly from the lower valve assembly, wherein the hydraulic line severing system includes an outer housing coupled to the upper valve assembly and a cutting member coupled to the lower valve assembly and slidingly disposed in a receptacle of the housing;
• wherein the housing includes a plurality of windows extending therethrough and configured to receive the hydraulic lines;
• wherein the cutting member includes a plurality of windows extending therethrough and configured to receive the hydraulic lines;
• and
• wherein each window of the cutting member has an upper edge comprising a blade configured to cut the one or more hydraulic lines extending therethrough.

A method comprising:

• (a) assembling a fluid transfer system on a surface vessel, wherein the fluid transfer system includes a first valve assembly including a first valve spool with a hydraulically actuated first isolation valve and a second valve assembly releasably coupled to the first valve assembly with a hydraulically actuated connector, wherein the second valve assembly includes a second valve spool with a second hydraulically actuated isolation valve;
• (b) coupling a fluid transfer line extending from the vessel to the fluid transfer system;
• (c) coupling the fluid transfer system to a jumper extending from a free-standing riser;
• (d) lowering the fluid transfer system through a moonpool in the surface vessel into the sea;
• (e) flowing hydrocarbon fluids from the free-standing riser through the jumper to the fluid transfer system, and then from the fluid transfer system through the fluid transfer line to the vessel.

A system for producing fluids from a subsea source to a surface vessel having a deck, the system comprising:

• a platform configured to be moveably coupled to the deck of the vessel;
• a fluid transfer system configured to be suspended from the vessel with a deployment/retrieval rigging, wherein the fluid transfer system includes:
• a first valve assembly including a first valve spool with a first isolation valve;
• a second valve assembly releasably coupled to the first valve assembly with a hydraulically actuated connector, wherein the second valve assembly includes a second valve spool with a second isolation valve;
• wherein the hydraulically actuated connector includes a hydraulically actuated collet connector coupled to the first valve assembly and a matin hub coupled to the second valve assembly;
• and
• a mechanical release system including a release plate and at least one rod, wherein the release plate is coupled to a plurality of release pins extending from the collet connector and the at least one rod;
• wherein each isolation valve has an open position allowing fluid flow through the valve assembly and a closed position restricting fluid flow through the valve assembly;
• a disconnect rigging coupled to the hydraulically actuated connector, wherein the disconnect rigging is coupled to the release plate of the mechanical release system and is configured to pull the release plate to mechanically disconnect the first valve assembly from the second valve assembly;
• an umbilical including a plurality of hydraulic lines extending from the vessel to the fluid transfer system;
• a fluid transfer line extending from the vessel to the fluid transfer system.