Closed-loop hydraulic running tool

A method for setting an inner wellhead member in a subsea wellhead housing, the method comprising:

• (a) providing a running tool having a setting piston, a release piston, an actuation sleeve with an actuation sleeve piston, and a latch sleeve with a latch sleeve piston, the setting, release, actuation sleeve and latch sleeve pistons each being in communication with a closed-loop hydraulic system;
• (b) providing the inner wellhead member with a locking element that moves between inner and outer positions, the locking element being in engagement with the actuation sleeve;
• (c) latching the running tool to the inner wellhead member with a latching element of the running tool and moving the latch sleeve from a release position to a latched position;
• (d) running the running tool and the inner wellhead member on a running string through a riser assembly until the inner wellhead member lands in the wellhead housing, an inner fluid passage being defined by the running string and the running tool and an outer fluid passage being defined by an annulus of the riser assembly and the running tool, the closed-loop hydraulic system containing a liquid that is isolated from the fluid passages by the setting piston and the release piston;
• then
• (e) locking the inner wellhead member to the wellhead housing by applying fluid pressure through one of the fluid passages to the setting piston, which increases a fluid pressure in the liquid in the closed loop hydraulic system between the setting piston and the actuation sleeve piston and moves the actuation sleeve to cause the locking element to move to the outer position;
• and then
• (f) applying fluid pressure through the other of the fluid passages to the release piston, which increases a fluid pressure in the liquid in the closed loop hydraulic system between the release piston and the latch sleeve piston and moves the latch sleeve out of engagement with the latching element so that the latching element can unlatch from the inner wellhead member.

A running tool for setting an inner wellhead member in a subsea wellhead housing, the running tool comprising:

• a setting pistol, a release piston, an actuation sleeve piston, and a latch sleeve piston, each piston comprising a first end and a second end;
• a closed-loop hydraulic system having a setting portion located between the second end of the setting piston and the first end of the actuating piston, the closed-loop hydraulic system having a release portion located between the second end of the release piston and the first end of the latch sleeve piston;
• an actuation sleeve joined to the actuation sleeve piston for movement therewith, the actuation sleeve moving from an unlocked position to a locked position in response to movement of the setting piston in a direction that increases fluid pressure in the setting portion of the closed-loop hydraulic system, the actuation sleeve urging a locking member of the inner wellhead member into engagement with the subsea wellhead housing when moving from the unlocked position to the locked position;
• a latch sleeve joined to the latch sleeve piston for movement therewith, the latch sleeve moving from latched position to unlatched position in response to movement of one of the release piston in a direction that increases fluid pressure in the release portion of the closed-loop hydraulic system, the unlatched position releasing the running tool from the inner wellhead member;
• a running tool body having an inner flow passage for receiving fluid pumped down a running string;
• an inner flow passage port extending from the inner flow passage for delivering fluid from the inner flow passage to the first end of one of the setting and release pistons;
• and
• an external flow passage port in the running tool for delivering fluid from an outer flow passage surrounding the running tool to the first end of the other of the setting and release pistons.