Patent Application
20150069752
The field of the invention is seal bores and more particularly where the needed space out variation is longer than the length of a standard tubular so that a modular design makes a seal bore to a desired length beyond the length of a standard tubular.
In certain deep completions of over 7,000 meters there exists a need for component space out that exceeds the capability of honing equipment with regard to producing an integral seal bore that can accommodate space out requirements of over 20 meters. Current honing equipment can reach 20 meters by honing the limit of about 10 meters from opposed ends of a tubular. Stock lengths of oilfield tubulars are in the order of 10 to 12 meters. To date the operating premise of those skilled in the art has been that the seal bore that can be reliably produced and operated should not have any connections because the inserted seal assembly would snag in the vicinity of where the pin nose contacts the box.
Prior art relating generally to seal bores can be found at U.S. Pat. No. 7,621,327, U.S. Pat. No. 7,516,791 (see
The present invention comprises the concept of a modular seal bore that allows attainment of any desired length as the seal bore is assembled and run in the hole. A variety of connection designs are contemplated to be able to join the modules and get the target length. The inside dimension where the modules contact comes in for special treatment to ensure that even if there is a dimensional difference across the contact location of adjacent modules that such difference is positioned sufficiently far from the seal assembly that can pass by in either direction so that there is no seal assembly damage or in the differential pressure capacity of the connection. In a preferred design the adjoining seal bore surfaces across the connection have a taper so that there is a smooth transition in the seal bore wall and that even if the pin and box tolerances all add up in the same direction that any such dimensional difference is spaced sufficiently far from the outside dimension of the seal assembly that there is no physical damage to the seal assembly. Generally the length of the seal assembly exceeds the length of the tapered surfaces so that sealing integrity is maintained as the seal assembly moves relative to the seal bore. Those skilled in the art will more readily appreciate these and other features of the present invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.
A seal bore is provided in a modular form so that a desired length of continuous seal bore can be provided with modules that are preferably secured to each other with threads. The modular concept allows overall seal bore lengths to go beyond the 20 meter limit that previously existing that could be attained with honing equipment entering opposed ends of a tubular. The modules abut each other as the threaded connection is made up. A transition zone extends in opposed direction on opposed sides of a connection that retracts the contact location between modules far enough so that even if the dimensional tolerances all go to the extreme in the pin and box that make the connection, a surface irregularity will be sufficiently small as to avoid seal stack contact that can result in potential seal damage. The seal stack length spans the transition zone to preserve sealing integrity.
A modular seal bore assembly is illustrated in
One way to address this potential problem that can damage the seals 28 is to provide tapers 32 and 34 in mirror image that extend to the transition line but can also transition to a parallel orientation with the seal bore 16 short of transition line 26. In this manner the transition line 26 is at a greater diameter than the seal bore 16 on either side of the tapers 32 and 34. The preferred taper angle is 2 degrees however larger or smaller angles can be used depending on the inside diameter of seal bore 16 and the amount of anticipated potential radial offset at the transition line 26 from the manufacturing process of a pin 18 and a box 20 that may be assembled to each other. The object is to recess the radial offset from the manufacturing process sufficiently that at the greatest envisioned offset there will not be a protrusion into the nominal seal bore 16 dimension taken outside the transition portions such as tapers 32 and 34. While the preferred angle for the tapers 32 and 34 is 2 degrees a range of 0.5 degrees to about 5 degrees is contemplated. It is also contemplated that at the top of the ramp, furthest from transition line 26 be rounded to avoid a line transition that could potentially do harm to a seal 28.
Those skilled in the art will appreciate that the present invention presents an ability to assembly seal bores at the surface to a desired length using modules of the same or different sizes that can be attached together, preferably with standard thread forms and more preferably a two-step thread. To make the modular concept operative at the transition lines the shape of the seal bore is altered on opposed sides so that any ledges caused by machining tolerances is within the recess so that movement of seals in either direction past the transition line will not damage the seal assembly or cause loss of sealing as the seal stack is longer than the mirror image transition segments. The transitions can be planar or arcuate or combinations thereof or can be other configurations that get the transition line out of contact with the passing seal assembly in opposed directions.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
