Wells – Processes – Placing or shifting well part
Reexamination Certificate
2001-02-23
2003-07-22
Neuder, William (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S077400, C166S085400
Reexamination Certificate
active
06595297
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This is the first application filed for the present invention.
MICROFICHE APPENDIX
Not Applicable.
TECHNICAL FIELD
The present invention relates in general to methods and apparatus for installing wellhead equipment in live wells, and, in particular, to a method and apparatus for inserting a tubing hanger into a tubing head spool installed on a live well.
BACKGROUND OF THE INVENTION
Production tubing is commonly used in oil wells for production purposes after an oil well has been completed or recompleted. Wells are frequently stimulated during the completion and recompletion processes. During well stimulation, high pressure fluids are pumped at high rates into one or more production zones of the well in order to fracture the hydrocarbon bearing formations to release trapped hydrocarbons. After the well has been completed or recompleted, fluid pressures in the well are typically greater than atmospheric pressure, and must be contained in order to prevent the loss of hydrocarbons to atmosphere.
In many cases, after a well is stimulated, well operators prefer to prepare the well for production without “killing” the well. A well is killed by pumping overbearing fluids into the well to contain fluid pressures in the well. Killing the well is generally considered undesirable because the kill fluids can potentially hinder production by disturbing the affects of the well treatment procedure. Consequently, production tubing is generally run into the live well using injection methods that are well known in the art. When the production tubing is run into a live well, a retrievable plug is first inserted into the bottom end of the tubing. This prevents hydrocarbons from escaping through the production tubing as it is run into the well. Jointed tubing or coil tubing may be used for production. In either case, tubing rams on blowout preventers (BOPs) are used to seal around the tubing while the tubing is being run into the well. If jointed tubing is used, the tubing is generally run through a snubbing unit, as is well understood in the art.
After the production tubing string has been run into the well, however, a tubing hanger must be set in the tubing head spool to suspend the production tubing string in the well. The tubing hanger is connected to a top end of the tubing string, and special equipment is required to run the tubing hanger into the tubing spool.
FIG. 1
is a schematic diagram of equipment that is frequently used to install a tubing hanger on a live well, generally indicated by reference
10
. The live well includes a casing spool
12
, to which a tubing head spool
14
is mounted. Tubing head spool
14
generally includes one or more tubing head valves
16
, which communicate with an annulus of the well in a manner well known in the art. Mounted to a top of the tubing head spool is a ram-type blowout preventer (BOP)
18
having a set of opposed tubing rams
20
, which are used to close an annulus of the well bore around a production tubing of a known diameter, and a set of opposed blind rams
22
which are used to completely block the annulus but cannot be used to close around tubing or other components. Mounted to the top of the ram-type BOP is an annular BOP
24
, available, for example, from Hydril Company, Houston, Tex. The annular BOP
24
employs a flexible rubber packing unit to provide pressure seal-off at the wellhead. The annular BOP can contain annulus pressure on an open hole or around tubular elements inserted into the well, such as production tubing
30
and tubing hanger
32
. The production tubing
30
and the tubing hanger
32
are inserted into the well using a landing joint
34
controlled by blocks
36
of a service rig, the remainder of which is not shown. Service rigs are well known in the art.
The paired BOPs shown in
FIG. 1
are capable of sealing around the production tubing
30
, a tubing collar (not shown), the tubing hanger
32
, and the landing joint
34
as they are respectively run into the live well bore. These respective components run through the BOPs to the tubing head spool
14
in the order specified. The landing joint
34
is screwed into a top of the tubing hanger
32
and is connected to the blocks
36
of the service rig. The respective components are then stepped through the BOPs
24
,
18
as the pipe rams
20
and the annular BOP
24
are opened and closed in sequence to permit the tubing hanger to be inserted into the tubing head spool while the live well is under pressure. Although this procedure is known to work reliably and has been approved by regulatory authorities, it has several disadvantages. First, the respective BOPs
18
,
24
add significantly to the height over the well, thus making the floor of the rig (not shown) very high and a potentially dangerous place to work. Furthermore, in certain jurisdictions safety laws require that a completion rig be moved away from the well before and during a well stimulation treatment, in order to provide adequate working space in the case of emergency. After well stimulation is completed, the rig must be moved back over the well, usually for the sole purpose of landing the tubing hanger and installing the wellhead after the tubing hanger has been landed in the live well. This is a costly operation, and it would be more cost-effective and beneficial if the well operator were able to release the service rig after the tubing is run into the well, to clear valuable work area and to reduce expense by releasing the service rig as early as possible.
Consequently, there exists a need for a method and apparatus for setting a tubing hanger in a tubing head spool on a live well which is easier and more cost-effective than the known method described above.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an apparatus for setting a tubing hanger in a tubing head spool on a subterranean well in which a fluid pressure in the well is greater than atmospheric pressure.
It is a further object of the invention to provide a method of setting a tubing hanger in a tubing head spool on a subterranean well in which a fluid pressure in the well is greater than atmospheric pressure.
It is yet a further object of the invention to provide a method and apparatus for setting a tubing hanger in a tubing head spool on a live well without the use of a service rig.
The invention therefore provides an apparatus for setting a tubing hanger in a tubing head spool in a subterranean well in which a fluid pressure is greater than atmospheric pressure. Such wells are commonly referred to as “live wells”. The apparatus comprises a landing spool which is mounted to a ram-type blowout preventer (BOP). The BOP is in turn mounted to the tubing head spool. The landing spool includes a flange for sealing attachment to the BOP and a top end through which a landing joint is reciprocated. The top end of the landing spool provides a high-pressure seal to prevent an escape of hydrocarbons as all the landing joint is reciprocated therethrough. A sidewall of the landing spool preferably includes a pressure bleed port to permit an equalization of pressure between the landing spool and the well, or an equalization of pressure between the landing spool and atmosphere. Lifting hooks or eyes are also provided on the sidewall of the landing spool, to permit the connection of flexible members, such as chains or cables, to support the landing spool before it is connected to a top flange of the BOP.
The top end of the landing spool through which the landing joint is reciprocated includes a packing cavity that receives high-pressure packing, such as Chevron packing. The high-pressure packing is retained in the packing cavity by a packing nut, such as a gland nut, well known in the art. The packing nut is preferably reinforced by a safety nut that engages a threaded outer perimeter of the top end of the landing spool. The safety nut has an inwardly-extending top wall that closely surrounds the landing joint and covers the gland nut to ensure that the high-pressure packing is not ejected b
Nelson Mullins Riley & Scarborough LLP
Neuder William
LandOfFree
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