Patent Application
20080169097
1. Field of the Invention
The present invention relates generally to a wellhead assembly for an oil and gas well. More particularly, the present invention relates to a wellhead assembly or hanger for a coiled tubing string which has annular communication.
2. Description of the Related Art
It is often desirable in the oilfield industry to insert a string of coiled tubing into the production tubing of a completed oil and gas well. The coiled tubing may be used for a number of purposes such as chemical injection, gas injection, cross sectional area reduction, or for carrying downhole equipment such as sensors, gauges, and pumps. Traditional coiled tubing is a continuous length of spoolable pipe, ranging in size from ¾″ to 3″ OD. Smaller diameters, such as ¼″ or ⅜″ OD, are sometimes referred to as a capillary string or an injection tubing string. As used hereinafter, such tubing will be referred to as an injection tubing string, although such use is not intended to limit the scope of the invention or exclude other comparable tubing strings.
It is also desirable to leave the injection tubing string in the wellbore for extended periods of time. This allows an operator, for example, to inject chemicals into the wellbore, on a continual basis, to enhance production or to inhibit corrosion, scale, hydrate or paraffin buildup in the well bore. U.S. Pat. No. 6,851,478 discloses a Y-body Christmas tree for use with an injection tubing string, thereby allowing for the essentially permanent installation of the injection tubing string. The Y-body Christmas tree provides convenient access for injecting coiled tubing into a tubing string without necessarily adding height to the wellhead or tree. The Y-body Christmas includes a vertical fluid flow bore for passage and containment of the production of oil and gas from the wellbore. The tree includes upper and lower master valves for controlling the passage of well flow through the tree and to an adjoining flow line. The Christmas tree also includes an independent angular coiled tubing bore that intersects the vertical flow bore of the tree between the upper and lower master valves, allowing the upper master valve to be cycled without being obstructed by a coil string.
The Y-body Christmas tree has at least two drawbacks. First, the tree is more expensive than a conventional Christmas tree. Furthermore, when the injection tubing string is installed in the production tubing, the lower master valve cannot be closed without severing the injection tubing string and requiring an expensive fishing job to remove the severed tubing string. In the event that the upper master valve begins to leak and needs to be repaired or replaced, an operator cannot obtain a double barrier required in many locations throughout the world by closing the lower master valve or installing a back pressure valve in the production tubing. As a result, an operator would have to mobilize a workover rig and/or lift boat so that the injection tubing string can be removed from the production tubing to allow the lower master valve to be closed and/or a back pressure valve to be installed. This is obviously a time consuming and expensive proposition.
Thus, there is a need for an alternative method for suspending an injection tubing string in production tubing that addresses the problems discussed above.
According to embodiments of the present invention, a wellhead assembly and method for an injection tubing string is provided herein. An exemplary embodiment of a wellhead assembly comprises a flange adapted to be connected to a wellhead, the flange having a longitudinal bore therethrough and an injection port extending radially through the flange and communicating with the longitudinal bore. The assembly includes a mandrel adapted to be inserted into the longitudinal bore of the flange, the mandrel having a longitudinal bore therethrough and a port for communicating with the injection port of the flange. The assembly further includes a hanger adapted to be connected to the upper end of an injection string, the hanger being further adapted to land in the longitudinal bore of the mandrel wherein the hanger includes a communication passageway for facilitating fluid communication between the port of the mandrel and the injection tubing string.
According to one embodiment, at least a portion of the mandrel's longitudinal bore serves as a polished bore receptacle. At least a portion of the flange's longitudinal bore also serves as a polished bore receptacle. The mandrel preferably includes seals for sealing the annular area between the flange's polished bore and the outer diameter of the mandrel. The seals seal the annular space above and below the injection port in the flange and the port extending through the mandrel. The injection tubing string hanger preferably includes seals for sealing the annular space between the mandrel's polished bore and the outer diameter of the hanger. The seals seal the annular space above and below the fluid passageway extending laterally through the hanger and the port extending through the mandrel.
In a preferred embodiment, the flange is inserted between the top of the production tubing head spool and the bottom of the Christmas tree. More particularly, the flange is connected beneath the lower master valve of the Christmas tree.
According to one embodiment, the injection tubing string is connected to the hanger by a ferrule fitting. A live swivel is preferably installed between the ferrule fitting and the injection string to allow rotation of the hanger without imparting rotation to the injection tubing string.
According to one embodiment, external threads are provided proximate to the lower end of the mandrel for connecting the mandrel to the back pressure valve thread profile in the production tubing hanger. The mandrel may also include an external seal for sealing the annular space between the mandrel and the production tubing hanger. The mandrel may include internal threads for receiving a back pressure valve in the longitudinal bore of the mandrel above the injection tubing string hanger. The hanger is preferably threadedly attached to the internal diameter of the mandrel to lock the hanger in place. Alternatively, the hanger may have a keyed connector which may be locked in place with minimal turning of the hanger relative to the mandrel. When locked in place, the hanger provides a straddled seal across the communication port with the mandrel. The hanger further provides a profile for connecting to a running tool. The hanger also provides annular flow area for production of oil and gas past the hanger and into the Christmas tree. Once installed, chemicals for treating the wellbore may be injected through the injection port of the flange, through the port in the mandrel, through the communication passageway of the hanger and into the injection tubing string.
Injected fluids may include gas, foamers, acids, surfactants, miscellar solutions, corrosion inhibitors, scale inhibitors, hydrate inhibitors, paraffin inhibitors, or any other chemicals that may increase the quality and/or quantity of production fluids flowing to the surface.
While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Illustrative embodiments of the invention and related methods are described below as they might be employed in the use of a wellhead assembly for an injection tubing string that extends into a production tubing string. In the interest of clarity, not all features of an actual implementation or related method are described in this specification. It will of course be appreciated that in the development of any such actual embodiment or method, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
Referring to
A plurality of bolt holes 24 are included about the outer circumference of the flange which will align with corresponding holes in the flanges of the production tubing spool (or tubing spool adapter if the latter is required) and lower master valve flange. By way of example, flange 15 includes 8 bolt holes for receiving bolts (not shown) to securely connect flange 15 between the production tubing head spool and the bottom of the lower master valve. Flange 15 includes an upper annular groove 22 and a lower annular groove 23 for receiving ring gasket seals (not shown), to seal the flange to the lower master valve and production tubing head spool.
Preferably, longitudinal bore 17 extending through the flange has the same diameter as the internal bore of the Christmas tree. For example, with 3½ inch production tubing, the Christmas tree will have a 3 1/16 inch internal bore extending therethrough and flange 15 will have a similar 3 1/16 inch inner diameter, or slightly less to accommodate easier insertion of the mandrel. At least a portion of internal bore 17 will serve as a polished bore receptacle to provide a sealing surface for mandrel 20.
Referring to
Mandrel 20 includes a flow port 40 for communicating with injection port 18. Mandrel 20 also includes upper annular recess 38 and lower annular recess 36 for receiving seal rings 52 and 54, respectively. Ring seals 52 and 54 seal the annular area between mandrel 20 and bore 17 of flange 15. Seals 52 and 54 keep injection chemicals from leaking between mandrel 20 and flange 15.
Bore 30 of the mandrel includes a threaded profile 42 for receiving the mating threads on injection tubing string hanger 25. One of skill in the art will appreciate that various types of thread profiles 42 may be used to attach and lock hanger 25 to mandrel 20. The mandrel may include an upper profile 44 for receiving a conventional back pressure valve (not shown). Mandrel 20 includes a polished bore section 55 that provides a sealing surface for tubing hanger 25.
Referring to FIGS. 1 and 4A-4C, one embodiment of the tubing hanger 25 of the present invention is shown in more detail. Hanger 25 includes an internal communications passageway 60 for communicating with mandrel flow port 40, injection port 18 and the injection tubing string. In a preferred embodiment, passageway 60 extends radially from its opening on the outer periphery of hanger 25 to the center of the hanger, where a portion of passageway 60 extends axially into the profile 62, thereby allowing communication with the top of the injection tubing string (not shown). In a preferred embodiment, hanger 25 includes an annular channel 75 which extends about the opening to passageway 60 to facilitate communications with flow port 40. Channel 75 allows communication between passageway 60 and flow port 40 even though passageway 60 is not radially aligned with port 40. In a similar manner, an annular channel (not shown) between mandrel 20 and flange 15 may be used to facilitate communications between injection port 18 and flow port 40. This annular channel may, for example, extend about bore 17 of the flange and/or the outer diameter of mandrel 20 (between recesses 36 and 38).
Hanger 25 includes annular grooves 72 and 74 for receiving seal rings 76 and 78 respectively to seal the annular space between hanger 25 and mandrel 20 above and below flow port 40, flow channel 75 and passageway 60. Thus, injected chemicals can be injected through injection port 18, through flow port 40 and into channel 75 where the chemicals will flow until it reaches passageway 60, whereafter the chemicals can pass into the injection tubing string connected to hanger 25.
The injection tubing string (not shown) is preferably attached to hanger 25 with a ferrule connector, which fits inside profile 62 of hanger 25. Hanger 25 also includes an enlarged profile 65 for receiving a live tubing swivel which allows hanger 25 to be rotated relative to mandrel 20 without imparting rotation to the tubing string. During installation, hanger 25 will preferably be rotated into locking engagement with mandrel 20. Live tubing swivels (not shown) are well known and are not described herein. Seals 76 and 78 on the hanger preferably seal inside polish bore 55 of mandrel 20.
To install the injection tubing string wellhead assembly on an existing well, the Christmas tree is disconnected from the production tubing head spool. Flange 15 is then inserted on top of the production tubing head spool (or tubing head adapter if present) and the tree is re-installed. Once the tree is re-installed, flange 15 will be connected to the bottom flange of the lower master valve. The mandrel is sized so that it can be run through the bore of the Christmas tree.
Hanger 25 and the injection tubing string suspended therefrom is run into the well after the Christmas tree has been nippled up to flange 15 and the tubing head spool. In one embodiment of the invention, the injection tubing string wellhead assembly is used with BJ Services' InjectSafe™ System which includes upper and lower injection strings, the lower injection string extends from a wireline retrievable surface controlled subsurface safety valve. The subsurface safety valve may be either a tubing retrievable safety valve or be a wireline insert safety valve installed, for example, inside a production subsurface safety valve. The upper injection string will sting into the InjectSafe™ downhole safety valve and will communicate with the lower injection string through a bypass which bypasses the valve mechanism of the safety valve. In a preferred embodiment, hanger 25 is run with the upper portion of the injection string. Once the downhole safety valve and lower injection string have been set in the well, the upper string is spaced-out and cut and connected to hanger 25 via a ferrule connector. A live tubing swivel may extend between the ferrule connector and the injection tubing string. A running tool is connected to profile 68 of hanger 25 and the injection string and hanger are lowered into the well through the Christmas tree until the hanger lands in profile 42 of mandrel 20. After the mandrel is connected to profile 42 of the mandrel, the running tool is disconnected from the hanger and removed from the wellbore.
The height of mandrel 20 is selected such that it will extend into the lower bore of the lower master valve but will not interfere with the operation (i.e., closing) of the lower master valve. Thus, both mater valves remain functional after installation of injection wellhead assembly 10, thereby allowing the master valves to be closed without cutting or damaging the injection tubing string suspended from hanger 25.
Referring to
In the exemplary embodiments of
Further referring to the exemplary embodiment of
A test port 26, as known in the art, extends radially through flange 15A in order to test the integrity of seals 27, 28 (uppermost seal) and 48. A plurality of bolt holes (not shown) are spaced about the other circumference of flange 15A which align with corresponding holes in the flanges of the lower master valve 115 and tubing head adapter 110. Any number of bolt holes may be included as desired.
As discussed in relation to previous embodiments, preferably, longitudinal bore 17A has the same diameter as the internal bore of the Christmas tree. However, flange 15A may have a slightly smaller diameter than that of the Christmas tree bore in order to accommodate easier insertion of the mandrel 20A. At least a portion of bore 17A will serve as a polished bore receptacle to provide a sealing surface for mandrel 20A.
Further referring to the exemplary embodiment of
As also discussed in previous embodiments, mandrel 20A includes flow port 40A for communicating with injection port 18A. Mandrel 20A includes annular seals 52A and 54A (and their corresponding recesses) for sealing the annular space between mandrel 20A and bore 17A of flange 15A. Seals 52A and 54A keep injection chemicals from leaking between mandrel 20A and flange 15A. Mandrel 20A may also include upper threaded profile 44A for receiving a convention back pressure valve (not shown). Mandrel 20A also includes a polished bore section 55A that provides a sealing surface for tubing hanger 25A.
In general, hanger 25A operates the same as discussed in relation to the previous embodiments. Therefore, chemicals can be injected through injection port 18A, through flow port 40A and into channel 75A (not shown in
In the exemplary embodiment of
Referring to
An annular groove 94 is located around flange 15B in between upper portion 90 and lower portion 92. Lower portion 92 has bolt holes (not shown) for receiving bolts 96 of tubing head adapter 110. Since lower portion 92 is short enough to receive existing bolts 96, there is no need to replace bolts 96 with longer bolts. As such, flange 15B can be readily applied to existing tubing head adapters. Integral needle valve 19 is located within upper portion 90, while test port 26 is located within lower portion 92. The design and operation of these components are identical to those embodiments previously discussed. Please note, however, that one ordinarily skilled in the art will appreciate that other flange profiles may be utilized depending on the bolt length and/or design of the head adapter.
The present invention may also be used with multi-completion wellbores (e.g., dual completions having two or more production tubing strings). For a multi-completion well, the flange would include two or more internal bores with each bore adapted to receive a mandrel and injection tubing hanger within the mandrel. The plurality of internal production bores through the flange may be of different diameters to correspond to different size production tubing (e.g., a 3½×2⅞ inch dual completion).
Referring to the exemplary embodiment of
Referring to
Mandrel 20C includes two flow ports 40C; each port 40C communicating with its respective injection port 18C. In addition to seal rings 52 and 54 used to seal the annular space above and below single flow port 40 of previous embodiments, the present embodiment utilizes one additional seal ring 56C. Seal ring 56C is used to seal the annular space below the lower flow port 40C, while seal ring 54C is used to seal the annular space above lower port 40. Ring seals 52C, 54C and 56C keep injection chemicals from leaking between mandrel 20C and flange 15C as previously discussed.
Hanger 25C also operates as previous discussed in relation to other embodiments. In this embodiment, however, in addition to seal rings 76 and 78 used to seal the annular space between hanger 25C and mandrel 20C above flow port 40C, two additional seal rings 86,88 are used to seal the annular space above and below the lower flow port 40C, respectively. Therefore, chemicals can be injected through each injection port 18C, through each corresponding flow port 40C and into each corresponding channel 75 (
The injection tubing strings 31 of
Although various embodiments have been shown and described, the invention is not so limited and will be understood to include all such modifications and variations as would be apparent to one skilled in the art, as well as related methods. For example, a wellhead assembly having three or more tubing strings and their respective flow paths can be envisioned within the scope of the present disclosure. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.
This application claims the benefit of U.S. Provisional Application No. 60/880,251, filed on Jan. 12, 2007, entitled “WELLHEAD ASSEMBLY FOR AN INJECTION TUBING STRING,” which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60880251 | Jan 2007 | US |
