Marine riser anti-collapse valve

A marine riser anticollapse valve assembly comprising,

• a body adapted for connection in series with a riser string at a position below sea level, said body having a bore through it and having an opening in its wall,
• a valve structure disposed exterior to said body wall about said body wall opening and including a cylinder having a first cylinder aperture and a second cylinder aperture, said cylinder having an opening in its wall in fluid communication with said body wall opening,
• a piston of weight W.sub.p disposed within said cylinder and having a first piston head having a lateral first cross sectional area A.sub.1 and means for slidable sealing within said first cylinder aperture and a second piston head having a lateral second cross-sectional area A.sub.2 and means for slidable sealing within said second cylinder aperture, said first and second cross-section areas being subject to sea water head pressure P.sub.h, said piston including an internal shoulder of a third lateral cross sectional area A.sub.3, said internal shoulder being subject to drilling fluid pressure P.sub.b of said riser via said body wall opening and said cylinder wall opening,
• whereby said valve structure remains closed so long as the sum of the weight of the piston and the product of drilling fluid pressure and said third lateral cross-sectional area is greater than the product of sea water head pressure and the difference between the lateral first and second cross section areas of said piston heads, or
• P.sub.b (A.sub.3)>P.sub.h (A.sub.1 -A.sub.2)-W.sub.p,
• and said valve structure automatically opens when the drilling fluid pressure drops to a level such that
• P.sub.b (A.sub.3)<P.sub.h (A.sub.1 -A.sub.2)-W.sub.p,
• and further including remotely actuatable hydraulic rod means disposed longitudinally aligned with said first piston head and when actuated for engagement with said first piston head for moving said piston longitudinally beyond said first cylinder aperture thereby opening said bore of said body to sea water via said body wall opening and said opening in said cylinder wall.

A marine riser anticollapse valve assembly comprising,

• a body adapted for connection in series with a marine riser at a position below sea level, said body having a bore through it and having an opening in its wall,
• a valve structure disposed adjacent the exterior of said body wall and including
• a cylinder, said cylinder having first and second apertures longitudinally spaced from each other and having an opening in its wall, said cylinder wall opening being in fluid communication with said body opening,
• a guide rod having a first end and a second end and having an outer diameter and extending through said cylinder via said first aperture and said second aperture and secured to said body above and below said cylinder apertures, said guide rod having a torus of an outer diameter greater than said rod outer diameter and disposed in said cylinder between said first aperture and said second aperture, said torus having a first annular surface on a first side and a second annular surface on a second side,
• a piston slidingly disposed about said guide rod and having a first piston head subject to sea water pressure and a second piston head subject to sea water pressure connected by a longitudinal member, said piston having lateral internal surfaces subject to bore pressure within said body, said piston having a first longitudinal bore through said first piston head and a first part of said longitudinal member, and a second longitudinal bore through said second piston head and a second part of said longitudinal member, said first and second longitudinal bores communicating with each other, said second longitudinal bore having an inside diameter larger than said outer diameter of said guide rod operably permitting longitudinal movement of said piston with respect to said outer diameter of said guide rod operably permitting longitudinal movement of said piston with respect to said guide rod, said first longitudinal bore having an inside diameter larger than said torus outer diameter operably permitting sliding longitudinal movement of said first piston longitudinal bore with respect to said torus,
• sealing means disposed between said first piston head and said first cylinder aperture, for slidable sealing of said first piston head to said first cylinder aperture,
• sealing means disposed between said second piston head and said second cylinder aperture for slidable sealing of said second piston head to said second cylinder aperture,
• sealing means disposed between said outer diameter of said torus and said second longitudinal bore for slidable sealing of said torus to said second longitudinal bore,
• sealing means disposed between said first piston head and said guide rod for slidable sealing of said first piston head to said guide rod,
• sealing means disposed between said second piston head and said guide rod for slidable sealing of said second piston head to said guide rod,
• a first flow passage in said guide rod extending from said first end of said guide rod to a hole in said guide rod disposed between said first side of said torus and said sealing means disposed between said first piston head and said guide rod,
• a second flow passage in said guide rod extending from said second end of said guide rod to a hole in said guide rod disposed between said second side of said torus and said sealing means disposed between said second piston head and said guide rod,
• an annulus between said guide rod and said first longitudinal bore and between said second annular surface of said torus and said means for sealing said first piston head to said guide rod defining a pressure chamber when said second piston head is in sealing engagement with said second cylinder,
• hydraulic circuit means for applying regulated opening pressure fluid to said pressure chamber via a first hydraulic line and said first flow passage and venting said second flow passage via a second hydraulic line to the sea,
• a differential pressure sensor means connected to said first line and responsive to a predetermined amount of change in pressure in said pressure chamber annulus proportional to a drop in pressure within said bore of said body for applying said regulated opening pressure via said second hydraulic line to said second flow passage and venting said first flow passage to the sea, operably causing said piston to move toward said second end of said guide rod operably opening at least one of said first and second apertures to the sea and the interior of said cylinder and the bore of said body.

Subsea apparatus comprising,

• a marine riser joint having an opening in its wall, said riser adapted for carrying drilling fluid within its walls and adapted for placement in a marine riser string beneath sea level, and
• a differential pressure sensor, said sensor including,
• a cylindrical structure affixed about the exterior of said riser joint wall about said opening of said joint wall, said cylindrical structure having an opening in its wall in fluid communication with said riser joint opening through which drilling fluid is applied to the interior of said cylindrical structure,
• a piston disposed within said cylindrical structure, said piston having a first area subject to sea water pressure, the product of said sea water pressure and said first area tending to move said piston in a first direction within said cylindrical structure, said piston having a second area subject to drilling fluid pressure and said second area tending to move said piston in a second direction within said cylindrical structure,
• a chamber within said cylindrical structure, the volume of said chamber being variable in proportion to the position of said piston within said cylindrical structure,
• a hydraulic sensor line communicating with said chamber, and
• means for applying hydraulic fluid of pressure of a predetermined amount to said chamber via said hydraulic line, whereby
• a change in pressure in said hydraulic sensor line is produced proportional to the difference in pressure between said sea water pressure and said drilling fluid pressure.

In combination, an apparatus body having an opening in its wall, said body having a first fluid within its walls, said body being disposed in a second fluid outside its walls, and

• a differential pressure sensor having,
• a structure disposed in said second fluid exterior to said body and secured about said opening of said apparatus body, said structure having an opening in its wall in fluid communication with said apparatus body opening through which said first fluid is applied to the interior of said structure,
• a piston disposed within said structure, said piston having a first area subject to the pressure of said second fluid, the product of said second fluid pressure and said first area tending to move said piston in a first direction within said structure, said piston having a second area subject to said first fluid pressure within said body, the product of said first fluid pressure and said second area tending to move said piston in a second direction within said structure,
• a chamber within said structure, the volume of said chamber being variable in proportion to the position of said piston within said structure,
• a hydraulic line communicating with said chamber, and
• means for applying hydraulic fluid pressure of a predetermined amount to said chamber via said hydraulic line, whereby
• a change in pressure in said hydraulic line is produced proportional to the difference in pressure between said second fluid pressure and said first fluid pressure.