Hydraulic blowout preventer assembly for production wellhead

Details Hydraulic blowout preventer assembly for production wellhead Hydraulic blowout preventer assembly for production wellhead

1999-10-29

2001-07-17

Shaver, Kevin (Department: 3754)

Valves and valve actuation

Blow-out preventers

Radial reciprocating ram

C251S063000

Reexamination Certificate

active

06260817

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a hydraulic production blowout preventer (“BOP”), its utilization as part of an integral production wellhead tree and the provision of BOP ram hydraulic chambers and a hydraulic fluid supply passageway which are positioned within the body of the tree.
BACKGROUND OF THE INVENTION
A typical, commercially available, prior art hydraulic BOP, incorporated into a conventional production wellhead tree, is illustrated in FIG.
1
. It will be noted that the assembly involves:
a BOP housing which forms opposed horizontal ram chambers and has threaded side connections, the BOP housing further having threaded top and bottom connections for connecting with other components of the production wellhead;
the BOP housing also forms a vertical central fluid production bore extending therethrough and the ram chambers extend between the external surface of the housing and the bore;
the ram chambers each contain a sealed ram comprising an inner elastomeric element and an outer, steel body;
a pair of external housings are connected to the side connections; and
each external housing forms an internal space or chamber which contains a sealed piston which supports a return spring—the piston is connected with the ram and a port is formed in the external housing outer end wall, for connection with a hydraulic line;
whereby hydraulic fluid, supplied under pressure to the external housing through the hydraulic line, advances the piston to drive the ram into the wellhead bore to assume a closed position for sealing around a rod string (not shown) and the return spring retracts the ram and piston to an open position when the hydraulic pressure is released.
It will be noted that the external housings form the hydraulic chambers for the BOP and must be fluid tight and of sturdy enough structure to contain the hydraulic pressure.
In a recent development, an integral production wellhead tree was disclosed in Canadian Patent No. 2,197,584, (the “'584 patent”), issued to the present applicant. This tree, shown in
FIG. 2
, involves integrating BOP and flow tee housings between top and bottom tubing head connections, as a unitary steel body. More particularly the tree comprises a forged or cast one-piece body forming a vertical fluid production bore and incorporates:
a bottom connection adapted to connect and seal with a tubing head;
a BOP housing, whose side wall forms opposed side openings or chambers for containing BOP rams, which chambers communicate or connect with the fluid production bore—it will be noted that the chambers can be described as being ‘buried’ in the side wall;
a flow tee housing forming a side opening communicating with the bore and having means for connecting with a flow line; and
a top connection for sealing and connecting with the next component of the production wellhead, usually a stuffing box.
The tree of the '584 patent further has a generally cylindrical configuration, which results in a relatively thick side wall when compared with prior production wellheads.
SUMMARY OF THE INVENTION
The present invention is concerned with providing a production wellhead assembly comprising:
an integral production wellhead tree having a BOP housing;
the side wall of the BOP housing forming a pair of horizontal opposed chambers, each extending between the housing's external surface and the tree's vertical bore;
the side wall of the tree forming a first passageway means, extending between the tree's external surface and the outer end of each chamber, through which hydraulic fluid may be supplied under pressure;
preferably a BOP ram and piston assembly is positioned within each chamber;
whereby hydraulic fluid may be supplied through the first passageway means to the chambers to bias the ram and piston assemblies to a closed position;
a pair of external housings is disengagably secured to the BOP housing side wall for closing and sealing the outer ends of the chambers;
each external housing preferably forms a sealed internal space or chamber;
preferably a shaft element is connected with each ram and piston assembly and extends into the internal space of the associated external housing; and
return means, such as a spring, are preferably provided in each external housing internal space, for acting on the shaft element to bias the ram and piston assembly to the open position.
It is to be noted:
that the BOP ram and piston are provided as assemblies which are wholly located within the housing chambers;
that the chambers and the hydraulic fluid passageway (which both must contain pressure) are buried within the tree side wall; and
that the external housings do not necessarily have to be constructed so as to contain pressure.
In addition, the assembly lends itself to a preferred combination with additional mechanical means for closing and locking the rams in the closed position as a safety “override”. More particularly, means, such as a threaded bolt, may be mounted to the external housing and extend into the housing's chamber, for biasing the shaft element and ram to the closed position and locking them there.
In a variant of the foregoing, the passageway means may be extended from the BOP housing through the external housing wall, to communicate with the external housing chamber at its outer end. When the shaft element is sealed to the external housing side wall, it now is converted to a piston. The hydraulic fluid pressure can then be applied not only to the outer face of the ram piston assembly but also to the shaft element piston outer face, thereby increasing the closing force. In this case, the external housing would, of course, have to be capable of containing the fluid pressure. However the assembly still lends itself to use with the mechanical override means.
In another variant, a second passageway means is formed through the BOP housing side wall and external housing side wall to supply hydraulic fluid into the external housing chamber to act against the inner face of the piston, thereby permitting the assembly to be opened with hydraulic fluid.
Broadly stated, the invention is directed to an improvement in a production wellhead assembly, comprising: an integral production wellhead tree having a side wall, an external surface and a fluid production bore extending therethrough; the tree comprising a hydraulic blowout preventer (“BOP”) housing having a side wall and external surface; the BOP housing side wall forming a pair of opposed chambers, having inner and outer ends, extending between the housing external surface and the bore, each chamber being operative to receive a sealed ram and piston assembly slidable between open and closed positions; the tree side wall forming hydraulic fluid supply first passageway means extending between the tree external surface and the outer end of each chamber, so that hydraulic fluid may be supplied therethrough to advance the ram and piston assemblies into the bore to the closed position; and means, disengagably secured to the BOP housing side wall, for closing and sealing the outer ends of the chambers.


REFERENCES:
patent: 2642942 (1953-06-01), Reynolds
patent: 3554480 (1971-01-01), Rowe
patent: 3817326 (1974-06-01), Meynier, III
patent: 4240503 (1980-12-01), Holt, Jr. et al.
patent: 4770387 (1988-09-01), Granger
patent: 4969390 (1990-11-01), Williams, III
patent: 5224557 (1993-07-01), Yenulis et al.
patent: 2197584 (1998-07-01), None
“Regan Blowout Prevents”, Regan Forge & Engineering Company, San Pedro, California (brochure), pp. 3704-3705.

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