Rotating control device with multiple seal cartridge

A rotating control device for use in a drilling system, the rotating control device comprising:

• a non-rotating tubular RCD housing enclosing an elongate passage;
• a mandrel which extends along the elongate passage, the mandrel having an axis and an end on which is mounted an elastomeric stripper which is located in the RCD housing and which is configured to seal against and rotate relative to the RCD housing about said axis with a drill pipe located inside the mandrel and extending along said axis;
• and
• a seal assembly which is configured to provide a substantially fluid tight seal between the RCD housing and the mandrel, the seal assembly comprising:
• a seal support housing with first and second seals which seal against an exterior surface of the mandrel, the first and second seals being spaced from one another generally parallel to the axis of the mandrel so that there is a space around the mandrel between the first and second seals, the first seal having a first side which is exposed to fluid at a pressure greater than or equal to the pressure of fluid in the RCD housing and a second side which is exposed to fluid in the space between the seals, the second seal having a first side which is exposed to fluid pressure in the space between the seals and a second side which is exposed to fluid pressure at the exterior of the RCD housing;
• a pressure stepping mechanism which pressurizes fluid to a pressure which is intermediate between the pressure at the first side of the first seal and the pressure at the second side of the second seal and supplies said fluid to the space between the two seals, the pressure stepping mechanism being integral with or secured to the seal support housing and comprising a cylinder containing a piston which divides the cylinder into an inlet volume and an outlet volume, the inlet volume receiving fluid from the volume in the RCD housing around the elastomeric stripper, or fluid which is pressure balanced with the fluid in the RCD housing around the elastomeric stripper;
• and
• wherein the seals, the seal support housing and the pressure stepping mechanism are located inside the RCD housing and are releasably attached to the RCD housing, and can be removed from the RCD housing together as a single unit.

A rotating control device for use in a drilling system, the rotating control device comprising:

• a non-rotating tubular RCD housing enclosing an elongate passage;
• a mandrel which extends along the elongate passage, the mandrel having an axis and an end on which is mounted an elastomeric stripper which is located in the RCD housing and which is configured to seal against and rotate relative to the RCD housing about said axis with a drill pipe located inside the mandrel and extending along said axis;
• a bearing assembly which supports the mandrel for rotation in the RCD housing;
• and
• a seal assembly which is configured to provide a substantially fluid tight seal between the RCD housing and the mandrel and to isolate the bearing assembly from pressurized fluid in the RCD housing, the seal assembly comprising:
• a seal support housing with first and second seals which seal against an exterior surface of the mandrel, the first and second seals being spaced from one another generally parallel to the axis of the mandrel so that there is a space around the mandrel between the first and second seals, the first seal having a first side which is exposed to fluid at a pressure greater than or equal to the pressure of fluid in the RCD housing and a second side which is exposed to fluid in the space between the seals, the second seal having a first side which is exposed to fluid pressure in the space between the seals and a second side which is exposed to fluid pressure at the exterior of the RCD housing;
• a cylinder containing a piston for pressurizing fluid to a pressure which is intermediate between the pressure at the first side of the first seal and the pressure at the second side of the second seal and supplies said fluid to the space between the two seals
• and being integral with or secured to the seal support housing, the piston divides the cylinder into an inlet volume and outlet volume, the inlet volume receiving fluid from the volume in the RCD housing around the elastomeric stripper, or fluid which is pressure balanced with the fluid in the RCD housing around the elastomeric stripper;
• and
• wherein the seals, the seal support housing and the pressure stepping mechanism are located inside the RCD housing and are releasably attached to the RCD housing, and can be removed from the RCD together as a single unit, whilst leaving the mandrel and the bearing assembly in place in the RCD housing.