Blowout preventer for coiled tubing

The present invention provides a blowout preventer in which a first set of hydraulic ports communicate with either side of a first piston coupled to a first piston rod, a second set of hydraulic ports communicate with either side of a second piston coupled to a second piston rod, and the first and second pistons and associated piston rods may be actuated independent of each other. Each piston rod is coupled to a ram, and preferably, the first piston rod is coupled to a pipe ram and the second piston rod is coupled to a slip ram. A feature of the present invention provides that all of these elements are contained within a single chamber extending laterally of and communicating with the bore of a BOP.

FIELD OF THE INVENTION 
The present invention relates generally to the field of blowout preventers 
(BOPs) and, more particularly, to a control device for a pair of rams 
which may be included within a multi-level blowout preventer stack that 
reduces the stack length and weight while providing independent control 
for each of the pair of rams. 
BACKGROUND OF THE INVENTION 
The use of blowout preventers in drilling, completion, workover, and 
production of oil and gas wells is well known. Such blowout preventers 
generally include a housing with a bore extending through the housing. 
Opposed chambers extend laterally of the bore in the housing and 
communicate with the bore. Rams are positioned in the chambers and the 
rams are connected to rods that are supported for moving the rams inwardly 
into the bore to close off the bore. This action divides the bore into a 
zone above the rams and a zone below the rams. The rods also serve to 
retract outwardly from the bore to open the bore. 
Various types of rams may be employed such as those which engage 
circumferentially around a pipe or tubular member for sealing engagement 
with the tube or pipe, while others are provided with cutting surfaces for 
shearing tubular members or cables which extend through the bore of the 
blowout preventer. 
Blowout preventers are also commonly used in coiled tubing systems. Such a 
BOP provides a means of holding the tubing and isolating the well bore 
pressure during a variety of conditions, including emergencies. The 
configuration of the BOP rams and sideport facility allows well-control 
operations to be conducted under a variety of conditions. 
Newer blowout preventers include four sets of rams, which may be referred 
to herein as a "Quad BOP". The system comprises a set of four stacked 
elements, each with a different function. Blind rams are shut when there 
is no tubing or tool string extending through the body of the BOP. Shear 
rams are designed to close on and cut through the tubing. Slip rams close 
on and hold the tubing, ideally without damaging the surface of the piping 
or other tubular member. Finally, pipe rams seal around the tubing when it 
is place. Each of the rams should only be actuated when the tubing is 
stationary; otherwise, damage to either the BOP or the tubing is likely. 
Stacking the four BOP elements one on top of the other has been found to 
unnecessarily extend the height of the Quad BOP. Further, the four 
elements are massive and consequently add a great deal of weight to the 
well head. In order to reduce the height and weight of the stack, certain 
Quad BOPs combine the primary actuators for each of the slip and the pipe 
ram. This has accomplished the intended purpose of reducing the height and 
weight of the stack but, unfortunately, eliminates the independent 
actuation of these elements. 
Although slip rams ideally do not damage the tubing surface of the tubular 
member through the BOP, it has been found that even a single actuation of 
the slips against the tubing can score the exterior surface of the tubing. 
In today's high performance operations at elevated pressures, this scoring 
can reduce the useful lifetime of the tubular member, particularly with 
coiled tubing. Thus, there remains a need for the capability to actuate 
the pipe rams without actuating the slip rams, with the actuation elements 
included within a single ram body. 
There remains a further need for a blowout preventer that is reduced in 
height and weight but which retains independently actuatable BOP rams. 
Such a blowout preventer should include the operations of two such ram 
elements, retaining their independent actuation, within a single ram body 
or chamber. 
SUMMARY OF THE INVENTION 
The present invention eliminates these and other shortcomings of the prior 
art. A first set of hydraulic ports communicate with either side of a 
first piston coupled to a first piston rod. A second set of hydraulic 
ports communicate with either side of a second piston coupled to a second 
piston rod and trie first and second pistons and associated piston rods 
may actuated independent of each other. Further, each piston rod is 
coupled to a ram. Preferably, the first piston rod is coupled to a pipe 
ram and the second piston rod is coupled to a slip ram. A feature of the 
present invention provides that all of these elements are contained within 
a single chamber extending laterally of and communicating with the bore of 
a BOP. 
In a preferred embodiment, the first piston rod is a hollow cylinder and 
the second piston rod is positioned coaxially within the first piston rod. 
As the first piston is actuated to close the pipe ram, the second piston, 
along with its associated cylinder, travels along with the first piston 
rod, positioning the slip ram poised for setting. Then, independently, the 
slip ram may be set by actuation of the second piston, if desired. 
Alternatively, the first and second piston rods may be positioned adjacent 
each other, rather than coaxially. Further, the hollow, cylindrical first 
piston rod may be sized to receive the second piston within the first 
piston rod. 
These and other features and advantages of the present invention will be 
apparent to those of skill in the art from a review of the following 
detailed description along with the accompanying drawing figures.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
Structure of a Preferred Embodiment 
FIG. 1 depicts a typical stack 10 that is commonly used on a well head 12. 
Above the well head may be included, in bottom-to-top order, a blowout 
preventer 14, a flow Tee 16, a standard quad BOP 18, a HydraConn connector 
20, a lubricator riser 22, a pair of striper/packers 24 and 26, an 
injector connector 28, and an injector 30 for the insertion of coiled 
tubing. Those of skill in the art will recognize that this is only 
intended to represent a typical stack, which is designed or modified to 
meet a specific application. Further, the various components selected to 
form the stack are typically joined together, such as by flanges for 
example, in a manner known in the art. 
The quad BOP 18 includes the stacked rams previously described, and shown 
in FIG. 2. The quad BOP 18 includes a set of pipe rams 32, slip rams 34, 
shear rams 36, and blind rams 38. It is desirable to shorten the height of 
the BOP, and consequently its weight as well. This has been accomplished 
in the past by combining the pipe ram actuator with the slip ram actuator. 
Unfortunately, there are occasions when independent actuation of the slip 
rams from the pipe rams is desirable. FIGS. 3, 4, and 5 depict the details 
of the structure of the present invention to accomplished this desired 
result. 
FIG. 3 depicts the desired installation of the combination pipe ram/slip 
ram 40 and associated structure. The structural details of the combination 
ram 40 will be described with regard to FIG. 4 and 5. As shown in FIG. 3, 
the combination ram 40 replaces the pipe rams 32 and slip rams 34 (FIG. 
2). A pair of combination rams 40 are called for, each within a laterally 
opposed chamber in communication with a bore 99 of the BOP. This permits 
complete engagement with a tubular member or pipe 98, located coaxially 
with a centerline 96 of the BOP. Further, the present invention may also 
be used for combining two other rams as well, other than the pipe and slip 
rams. 
Referring briefly to FIGS. 7A and 7B, the currently preferred structure of 
the pipe rams and the slips is depicted. FIG. 7A is an exploded view in 
partial section, while FIG. 7B depicts the various parts in an assembled 
condition. The various parts include a set of slip inserts 50, a front 
seal 51, and a horseshoe seal 52. The top slip insert is threaded or 
otherwise appropriately coupled to a pusher 54 and the lower slip insert 
is coupled to a pusher 55, each within a ram body 53. The pushers 54 and 
55 serve to push the slip inserts 50 forward. A guide 56 guides the 
assembly and moves the pushers 54 and 55. As shown in FIGS. 7A and 7B the 
pushers 54 and 55 are preferably of different lengths, but only for ease 
of assembly of the parts within the ram body 53. Those of skill in the art 
will appreciate that the assembly further includes various seals and 
retainers in a manner known in the art. 
FIG. 4 provides a detailed section view of the structure of the combination 
ram 40. The combination ram 40 attaches to a section 60 of the BOP body. 
Within the combination ram is an inner coaxial rod 62 (not shown in 
section) that actuates the slips relative to the movement of the pipe ram 
body. The rod 62 is connected to a slip ram piston 64 within a cylinder 
66. The cylinder 66 is attached to a main operator piston rod 68 and the 
rod 68 is threaded into a pipe ram piston 70. Although the piston rod 68 
is preferably formed in two parts, both parts are shown in FIG. 4 
designated as rod 68 for clarity since it functions as one piston rod. The 
rod 68 is keyed into the back side of a ram body 72 to move the ram back 
and forth within a cylinder 74. 
The assembly further includes a manual locking assembly 76 to manually 
override hydraulic actuation of either or pipe rams. A manual locking 
assembly 78 prevents the slips from the retracting when the assembly 78 is 
actuated. 
A set of hydraulic ports is also provided. A port 80 provides hydraulic 
pressure to close the pipe ram. The port 80 connects to a cylinder chamber 
82 which, when pressurized, moves the piston 70 to the right (as seen in 
FIG. 4). The piston 70 is threaded onto the rod 68, which in turn is 
threadedly connected to the cylinder 66. Consequently, the slip actuation 
assembly also moves to the right. A port 84 is also provided which is 
coupled to a cylinder chamber 86 for opening the pipe ram. 
A port 88 is connected to a cylinder chamber 90 to actuate the piston 64. 
Pressurization of the cylinder chamber 90 moves the piston 64 to the 
right. This motion abuts the inner rod 62 to close the slips. A port 92 is 
also provided to open the slips by pressurizing a cylinder chamber 94 and 
moving the piston 64 to the left. 
Operation of the Preferred Embodiment 
Now that the preferred structure of the present invention has been 
described in detail, the preferred method of operation will now be 
described. The condition of the combination ram 40 depicted in FIG. 4 
shows the position of the movable elements with the pipe ram open port 84 
and slip open port 92 having been pressurized. In other words, the piston 
64 and the piston 70 are currently in their full, left-most position. 
FIG. 5 show the position of various portions of the combination ram 40 with 
the pipe ram shut and the slips still retracted. The ellipses around the 
legends "PIPE RAMS CLOSE" and "SLIPS RELEASE" indicate that the ports 80 
and 92 have been pressurized. It should also be understood at this point 
that the ports 84 and 88 serve as the discharge ports for hydraulic fluid 
during this evolution. The port 92 has been pressurized to ensure that, 
with the pipe ram closed, the slips remain retracted until affirmatively 
actuated. 
With the port 80 pressurized, the cylinder chamber 82 is pressurized, 
forcing the piston 70 to the right until the front seal 51 contacts and 
seals around a pipe within the BOP, shown schematically in FIG. 5 as the 
centerline 96 of the bore 99 (see FIG. 3). The inner coaxial rod 62 and 
the main operator piston rod 68 have been moved together to the right as a 
unit. Note the relative positions of the manual actuator 76 and the 
cylinder 66 in FIGS. 4 and 5. However, with the port 92 pressurized, the 
piston 64 has not moved relative to the cylinder 66, and the slip inserts 
50 have not contacted the pipe. 
Referring now to FIG. 6, at this point the slips have been closed. This is 
done by pressurizing the slips set port 88, thus pressurizing the cylinder 
chamber 90. This moves the piston 64 to the right. Since the inner coaxial 
rod 62 is coupled to the piston 64, the rod 62 also moves to the right, 
sliding within the main operator piston rod 68. This forces the guide 56 
forward until the slip inserts 50 contact the pipe, shown in phantom in 
FIG. 6 as the pipe 98 (see FIG. 3). 
The principles, preferred embodiment, and mode of operation of the present 
invention have been described in the foregoing specification. This 
invention is not to be construed as limited to the particular forms 
disclosed, since these are regarded as illustrative rather than 
restrictive. Moreover, variations and changes may be made by those skilled 
in the art without departing from the spirit of the invention. 
For example, the preferred embodiment has been described as having coaxial 
actuation rods 62 and 68, with pistons 70 and 64 in tandem. Those of skill 
in the art will recognize that the rods 62 and 68 need not be coaxial, but 
could be placed side by side to carry out the present invention. Further, 
the main actuation rod 68 could easily be modified to include a slip 
actuation piston 64 within it, so that the pistons would not be in tandem. 
Other embodiments are certainly possible, fully within the scope of the 
present invention, so long as the rams are independently actuatable within 
one ram enclosure. 
Furthermore, the present invention has been described with regard to pipe 
and slip rams. However, the present invention is equally applicable to 
blind and shear rams, or any pair of the four rams described, within the 
scope of the present invention. The present invention has also been 
described with regard to coiled tubing but is equally applicable to other 
types of pipe or tubing.