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Description  |
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FIELD OF THE INVENTION
This invention relates to a well-head drilling system for deep water (done
with floating drills) so as to enable such wells to be worked for oil, in
that it provides a novel interface for completing equipment.
BACKGROUND OF THE INVENTION
In recent years the search for oil and gas fields has spread to waters ever
deeper offshore of the mainland. As the depth of water becomes greater,
drilling has been done more frequently with the aid of floating drills
instead of from fixed platforms, for reasons of cost. Particularly, drills
that can be dynamically placed have been used, thus avoiding trouble with
anchoring systems.
Drilling in deep water brings up a host of difficulties Which has served to
highlight the inefficiency of the equipment usually employed in such deep
water operations. However, the system of bases that make up the well-head
now used in deep water drilling is quite different from that used for
shallow water drilling, having been adapted so as to make operation with
dynamically placed drills easier since they do not need guiding cables.
Another point which makes drilling difficult in deep water is the question
of the degree of tilt of the base, which tilt will bring about a like tilt
in the high pressure housing. Since a high pressure housing is used as the
support for the blow-out control equipment, the tilt may make the blow-out
control operate under stress and thereby lead to premature and undesirable
wear of its parts. Therefore control over the tilt of the base system must
be exercised. In deep water, such control can be accomplished by means of
television cameras, since divers cannot be employed, and in order to carry
out such monitoring, visibility must be good so that corrections and other
adjustments may be made at the surface by remote control. Such cameras can
be installed in the column around which the bases are fixed, as in remote
control vehicles. This question of visibility has been taken into account
since in the previous base systems gravel would gather at points where
visibility had to be best, since the bases are low and return flow would
take place through the mouth of the funnel. Therefore, guide-funnels were
increased considerably in size and return was made sideways to prevent
level gauges from becoming covered over with gravel. Thus, by altering the
size of the funnel-guides as well as by altering the base system, it
became possible to better place other equipment during installation.
However, improvements in the previous state of the art had not overcome
problems in connection with working the wells regarding the next stage of
preparation of wells for such purpose.
Among the principal difficulties of previous methods was that of the
guide-funnel mentioned above. Because of its greater size (although this
made it easier to install the blow-out control equipment), it was
difficult to put in wet Christmas trees (which is an art-recognized
expression for production well valve control systems). The guide-funnel
therefore had to be withdrawn in order to install a wet Christmas tree. On
the other hand, without a guide-funnel other difficulties in the
deep-water placing of equipment arise, particularly regarding coupling
tolerances, especially of the parts that make up the wet Christmas tree.
SUMMARY OF THE INVENTION
One of the purposes of this invention is to provide a system to enable
thoroughly safe installation to take place of deep well production
equipment without the aforementioned difficulties, for the precise
locating of fitting points of the equipment to be assembled (production
equipment) upon the equipment already in place (high pressure housing).
Another purpose of the present invention is to provide a process to be used
in seating a completion (production) base upon the high pressure housing
and to do this so that the parts that fit together do so thoroughly
safely, and which also provides for protection of the free end of the high
pressure housing and for removal of the guide-funnel from the permanent
base guide.
In accordance with this invention, when drilling of the well with a
dynamically placed drill is finished, the high pressure housing is
protected by a cover which also functions to guide completing equipment to
be installed in the well-head after the permanent base guide-funnel has
been removed or withdrawn with the aid of remote control vehicles.
Withdrawal of the aforesaid guide-funnel leaves free space in which to
couple the completion base which, since it lies upon the high pressure
housing, makes it easier to tie in the tolerances concerned, to fit in the
production well valve control system (i.e., the wet Christmas tree). Since
the completion base has posts, this will enable use to be made of the
guide cables from the anchored drill rigs, thereby making further
operations easier to carry out, for which operations the methods employed
are already known and have been used in practice.
The above objects and advantages of the present invention can be
accomplished by a process for oil well drilling and completing operations
in deep water which allows an oil well drilled in deep water to start
producing, said operations being conducted from a dynamically placed
vessel, comprising,
(a) providing a permanent guide base (9) on the sea bottom containing a
high pressure housing (13) having an upper free end (15) adapted to
receive safety, drilling, and production (completion) equipment, the upper
free end of the high pressure housing being covered by a protective cover
(17) having an external conical part (18), said permanent guide base (9)
also having attached thereto, by means of a releasing device, a releasable
guide-funnel (10) which covers and protects the upper free end of the high
pressure housing during drilling of the well but which prevents said
production equipment from being installed because of its size and shape:
(b) withdrawing said releasable guide-funnel, after drilling operations are
finished, by means of a remote control vehicle which activates said
releasing device, thus leaving said protective cover exposed which,
because of said conical part, is capable of performing the same guiding
work as said guide-funnel after said guide-funnel has been removed: and
(c) lowering a production (completion) base (20) onto said permanent guide
base (9) whereby said protective cover protects the upper free end of the
high pressure housing from damage during said lowering step.
Equipment for performing the above process is also disclosed, including the
permanent guide base having high pressure housing, a protective cover
thereover, and a releasable guide-funnel. The guide-funnel is released
through a releasing device activatable by remote control.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a part section vertical view of the base system with the
protecting cover on.
FIG. 2 is a detailed side section view of the guide funnel lock.
FIG. 3 is a part section vertical side view of the base system able to
receive the production base.
FIG. 4 is a part section vertical side view of the base system being laid
upon the production base.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a temporary base 1, lying upon the sea bottom. To further
strengthen the well-head assembly, a pipe pile, 3, is driven into the sea
bottom by blasting, the pipe pile being in turn attached to the temporary
guide base, 1, by means of housing, 2, bolted by bolts, 4, to base 1,
indirectly, through the pipe pile, 3. The entire operation is remotely
accomplished with the aid of closed-circuit television, the tilt of the
assembly in particularly being watched by consulting level gauge, 6,
which, since it lies above outlet hole, 5, and the returning gravel,
stands clear of any solid particles that might gather thereon.
In keeping with usual practice followed in deep water drilling work, the
first stage of well preparation is the drilling thereof, when the casing.
8, fixed to the permanent guide base, 9, by means of low pressure housing,
7, is lowered. The casing, 8, is welded to the aforesaid low pressure
housing, 7, and then cemented throughout its whole length.
Usually this is followed by the second stage of well drilling, and when
this is finished, the high pressure housing, 13, is lowered onto the
permanent guide base, along with its respective casing, 14. Once more,
cementing of the casing takes place and a firm base is secured to support
the casings to be put into the well, and anchored inside the aforesaid
high pressure housing, 13.
As in common knowledge among those skilled in the art, the high pressure
housing, 13, has at its top, 15, a shape and seating (ledges, slots, and
groove for sealing ring to fit in) suitable for connecting and sealing,
respectively, the safety and drilling equipment (blow-out controller) and
the production equipment (in the present instance, the wet Christmas tree)
and later connection between the well and the surface.
Therefore, the upper free end, 15, of this high pressure housing must be
protected, and it must not be banged or damaged in any way. When the well
is being drilled, the guide-funnel, 10, releasably attached to the
permanent guide base 9 (FIG. 1), is present to provide such protection, by
guiding the connector of the blow-out control equipment. However, the
guide-funnel prevents the wet Christmas tree from being installed, because
of its size and also its shape. Therefore, in order to complete the well,
the guide-funnel. 10, must be withdrawn or removed, which leaves the upper
free end, 15, of the high pressure housing. 13, completely unprotected and
vulnerable to damage at the areas mentioned above.
To overcome this problem, this invention provides a strong protective
cover, 17, which not only protects the upper free end, 15, of the high
pressure housing but, since it has an external conical shaped section, 18,
enables well-head equipment to be fitted in easily, thus replacing
guide-funnel, 10, in its channelling or guiding function.
Basically, such protecting cover, 17, consists of a hollow part which at
its lower end is cylindrical in shape, 19, and welded at its top end to a
top cut-off cone-shaped part, 18, ending up at its top as a circular level
part which may be either entirely closed or provided with a hole (though
this is not essential for operation of the device, having been subjected
to such alterations merely to make installation and removal easier).
Essentially, the protective cover. 17, covers the upper free end of the
high pressure housing, 13, thereby preventing the latter from being banged
by other moving parts or tools during installation of production base, 20,
which will be described hereafter (FIG. 4). Likewise, the placing of the
cover, 17, upon the high pressure housing, 13, and also the later removal
thereof, is effectively done by means of special tools, description of
which is beyond the scope of this specification. It should be mentioned
that the conical part, 18, of cover, 17. performs the same guiding work as
that done by guide-funnel 10, after the latter has been removed, though
their conical features are inverted, that is, opposite to one another.
To carry on with the producing well assembly job--once cover, 17, has been
installed, guide-funnel, 10, may be withdrawn. To do this, however, there
must be some sort of method to disconnect guide-funnel, 10, from its
permanent guide base. Such method is depicted in FIG. 1, under number 11,
shown in greater detail in FIG. 2, and described below.
As is shown in FIG. 2, there is a pin, 21, kept expanded by a spring, 22, a
housed in hole, 23, in the bottom cylindrical part, 24, of guide-funnel,
10, which therefore locks said bottom part, 24, against top plate, 25, of
permanent guide base, 9. Upon completion of the well, after cover, 17, has
been put on high pressure housing, 13, a remote control vehicle is sent to
the well-head to pull out locking pin, 21, by working cotter-pin, 26,
which is connected to stem, 28, in such a way that it can be withdrawn, by
means of connecting part, 27, which stem, in turn, ends in a grip, 29A,
upon which the aforesaid remote control vehicle, not shown, will operate
directly.
As is easy to see from FIG. 2, the top plate, 25, of permanent guide base,
9, has a supporting part, 29, attached to its underside, which part is a
block provided with a hole through which the shank of cotter-pin, 26,
passes, and the part thereof within the said hole is provided with a male
thread, 30, which matches a corresponding female thread, 31, inside the
aforesaid hole of the supporting part, 29. When grip, 29A, is worked, the
twisting movement exerted upon shank, 28, will be transferred to shank,
26, of the cotter-pin which will cause matched threads, 30 and 31, to turn
and thereby bring about sure shifting of aforesaid cotter-pin, 26, in such
a way that its flattened end, 32. Will press against: pin, 21, until such
pin is fully held inside hole, 23, with its free end flush with the
outside of part, 29, which will enable the lower cylindrical part, 24, of
guide-funnel, 10, to move upwards. Next, with pins, 21, held, an extractor
tool (not shown) is inserted into the seat of the top of funnel, 10 (FIG.
1, detail, 12), and, by pulling slightly, guide-funnel, 10, can be
uncoupled and then removed. As depicted in FIG. 3 (side view) the system
is then ready to receive the completion base which will lie directly upon
permanent guide base, 9.
As shown in FIG. 4, once guide-funnel, 10, has been withdrawn, the top part
of the base assembly has enough space for the completion base, 20
(previously also referred to as the production base) to be easily lowered
down. In accordance with this invention the supporting point for the
completion or production base, 20, upon the now assembled bases, is the
outside ring. 16, of the high pressure housing, 13, which is specially
adapted for such purpose. Hence, once the completing base 20, has been
firmly lowered upon permanent guide base 9, and guide posts, 33, also
having been put in place, and completion base 20 being in a well defined
position and connection, 34, for the flow-line being supported thereby,
installation of the wet Christmas tree and of the flow, line (which will
connect the rig to the surface) will be made easier, while sound tolerance
figures are attained for the several dimensions of the coupled parts,
without any danger of damage being done to the connecting points. This is
entirely possible if the knowledge and the equipment provided in
accordance with this invention are used, since now the guide-posts, 33,
will enable precise positioning of the various other items of equipment to
take place, as, for instance, the wet Christmas tree. It should be noted
that before lowering the aforesaid other items of equipment, guided by
guide-posts, 33, cover, 17, must be withdrawn with the aid of a remotely
controlled tool, which is quite easily done since said cover, 17, is put
upon the high pressure housing, 13, just by laying it thereon, no type of
fastening being resorted to. As in the case of the drilling operations,
these operations for the placing of completing and production items can be
done by means of floating anchored drill-rigs.
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