Background of the Invention
The present invention generally relates to well apparatus and, in a preferred embodiment thereof, more particularly relates to protective apparatus for use in shielding well lines, such as control, chemical and balance lines, against damage in offshore well applications.
Offshore oil and gas well apparatus, particularly where a floating rig is used, is susceptible to a variety of fabricational, testing and operational problems due to the often harsh marine environment in which it must reliably function. For example, in a conventional construction thereof, a tubular riser having an open top end is typically run from the rig downwardly to a large blowout preventer structure (BOP) on the sea floor.
Coaxially disposed within the riser, and creating an annular space therein, is a smaller diameter tubing string which extends downwardly through the sea floor into the fluid production zone and is used for testing or production as the case may be. At its upper end the tubing string extends upwardly through the open upper riser end and through an opening in the rig floor and the rotary table thereon.
In the blowout preventer structure on the sea floor are a variety of tubing and riser-mounted controllable structures, such as a retainer valve, a subsea testing tree (SSTT), a pipe sealing ram structure, and a blind shear ram structure. To operate these structures, and for a variety of other purposes, a series of well lines are run down the tubing/riser annulus and operatively connected to their associated tubing and riser mounted structures. Such well lines typically have elongated tubular or cylindrical configurations and may be, among other things, control lines, chemical lines, balancing lines, conduit-shrouded electrical lines, fiberoptic cables, or wire lines.
One of the problems that potentially may be encountered in this type of well construction is the leakage of gas from the production zone upwardly into the tubing/riser annulus. Such gas could be a poisonous one, most notably hydrogen sulfide, that passes upwardly through the annulus and out the open upper riser end to endanger the rig crew, or another type of gas such as carbon dioxide or hydrocarbon gas. Regardless of what type of gas finds its way into the tubing/riser annulus another problem is potentially created--namely, if the gas leakage flow rate is high enough it can cause a loss in buoyancy in the rig platform and cause it to sink.
The conventional approach to preventing gas leakage into the tubing/riser annulus has been to install on the riser a sealing ram structure disposed beneath the subsea tree within the blowout preventer structure on the sea floor. In this ram structure are a pair of opposing horizontally drivable ram members having semicircular sealing faces in a facing relationship with opposite side surface areas of the tubing structure positioned beneath the lower terminations of the well lines extending down the tubing/riser annulus.
In their normally open orientation, the ram members are held generally outwardly of the riser. However, when gas leakage into the annulus is detected, the ram members are driven to their closed positions in which they are in forcible sealing engagement with opposite external side surface portions of the tubing string and close off the annulus to prevent upward gas leakage flow therethrough past the closed ram members. Since if gas leakage into the annulus occurs it typically does so near the sea floor, below the sealing ram members, this shutoff approach generally functions well for its intended purpose.
But, if the gas leakage into the tubing/riser annulus occurs above this sealing ram structure (and above the emergency blind shear ram structure typically installed above it), for example via leakage through the tubing into the annulus, the typical action taken is to simply evacuate the rig since the leaking gas simply flows upwardly through the annulus and out the open upper end of the riser.
Another problem which can occur on a floating rig relates to potential damage to the aforementioned well lines where they pass with an upper end portion of the tubing through an opening on the rig floor and the rotary table thereon. Due to the often violent wind and wave-caused motion of the floating rig it is not uncommon for the surface of this opening to bang into the tubing portion extending upwardly therethrough and damage or completely disable the function of one or more well lines by crushing it against the outer side surface of this tubing section. This, of course, can hinder or terminate the particular well operation under way prior to this well line damage.
From the foregoing it can be seen that it would be highly desirable to solve these problems commonly associated with a variety of floating offshore oil and gas rigs. It is accordingly an object of the present invention to provide apparatus which eliminates or at least substantially reduces these two above-mentioned problems.
Summary of the Invention
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, apparatus is provided for protecting a longitudinal portion of a well line member extending externally along and generally parallel to a well tubing string, representatively a tubing string used in an offshore floating type well rig, from impact damage.
From a broad perspective the apparatus comprises first and second cooperable members. The first member has a passage extending therethrough along an axis, and is coaxially connectable in the tubing string to define an axial section thereof. An axial portion of the first member has an exterior side surface positioned to extend laterally outwardly beyond the exterior side surface of the tubing string and has a recess configured to laterally receive the longitudinal well line member portion to be protected. The second member is removably receivable in the first member recess and is operative, when received therein, to laterally outwardly shield the longitudinal well line member portion within the recess.
Three embodiments of the second member are representatively provided--a first embodiment formed entirely from an essentially rigid material, a second embodiment formed entirely from a resilient material, and a third embodiment having a rigid main body portion and a resilient inner side section. Each second member embodiment is preferably configured to be axially inserted into the first member recess and to complementarily fill the entire recess area unoccupied by the longitudinal well line member portions therein.
In one representative application of the invention, the protective device, with the rigid first embodiment of the second member disposed in the side recess of the first member, is installed in the tubing string of a floating offshore rig and disposed within the vertical opening extending through the rig floor and the rotary table on the top side thereof to shield longitudinal well line portions passing through the opening from impact damage from its periphery during wind and wave--created movement thereof relative to the tubing string.
In another representative application of the invention, the protective device, with either the second or third resilient embodiment of the second member disposed in the first member side recess to protect the longitudinal well line portions extending therethrough, is disposed in an upper end portion of the riser structure of the rig between a pair of conventional sealing ram members carried by the riser. A gas bypass conduit communicates with the tubing/riser annulus below the sealing rams and extends horizontally away from the riser.
In the event that the leakage of gas into the tubing/riser annulus is detected, the ram members are driven horizontally through a closure stroke to forcibly engage and form an annular seal around the exterior side surface of the protective device, to thereby sealingly close off the annulus to upward gas flow past the closed ram members. Due to this annulus closure, the upwardly flowing gas is forced to flow outwardly through the bypass conduit for discharge a safe distance away from the rig.
The at least partially resilient second protective device member protects the longitudinal well line portions within the first member recess from damage due to the large transverse forces exerted on the protective device by the ram members. Additionally, the ram force causes the second member to create around the longitudinal well line portions a resilient seal that essentially prevents gas flow upwardly around the peripheries of such longitudinal well line portions.
Brief Description of the Drawings
FIG. 1 is a highly schematic, partly elevational cross-sectional view through a vertically foreshortened longitudinal portion of tubing and related riser sections of a floating offshore well rig;
FIG. 2 is an enlarged scale cross-sectional view, taken along line 2--2 of FIG. 1, through a well line protective device embodying principles of the present invention;
FIG. 2A is a view similar to that in FIG. 2, but with an insert portion of the protective device removed for illustrative purposes;
FIG. 3 is a reduced scale cross-sectional view through the main body portion of the protective device taken along line 3--3 of FIG. 2A;
FIG. 4 is a side elevational view of the main body portion taken along line 4--4 of FIG. 2A;
FIG. 5 is an enlarged scale cross-sectional view, taken along line 5--5 of FIG. 1, through a sealing ram structure incorporating therein an alternate embodiment of the well line protective device; and
FIG. 6 is a cross-sectional view of a modified version of the insert portion of the FIG. 5 well line protective device.
Detailed Description
Schematically depicted in vertically foreshortened form in FIG. 1 are various portions of a floating type offshore well apparatus 10 including a rig floor structure 12 disposed above the water's surface 14 and having a rotary table 16 disposed thereon with an opening 18 extending vertically through the rig floor 12 and the rotary table 16. Positioned beneath the rig floor 12 is a vertically oriented hollow tubular riser 20 having an open top end 22 and extending downwardly to a conventional blowout preventer structure (not shown) on the sea floor. A tubing string 24 extends downwardly through the rig floor and rotary table opening 18 and the riser 20, with an annular space 26 being formed between the inner side surface of the riser 20 and the portion of the tubing string 24 extending through the riser 20.
Tubular well line members, representatively a control line 28, a chemical line 30 and a balancing line 32 (see FIGS. 3 and 5 also), vertically extend externally along and generally parallel to the tubing string 24, with the well line members being connected at their lower ends to various conventional equipment (not shown) adjacent the lower end of the riser 20. As used herein, the terms "well line", "well line member" and the like refer to any of the various elongated structures, such as control lines, chemical lines, balancing lines, wire lines, fiberoptic lines, conduit-shrouded electrical lines, etc. which, in addition to the tubing string, are run down the casing to facilitate the control, operation, testing, powering, servicing, inspection, etc. of the well.
A problem often encountered in floating offshore rigs such as the rig 10 is that due to often severe wind and wave conditions, the surface of the rig floor/rotary table opening 18 can be brought into forcible contact with the longitudinal portions of the well lines 28,30,32 passing through the opening 18, with the result that the well lines can be crushed against the tubing string or severed.
Referring now to FIGS. 1-2A, 3 and 4, in the present invention this problem is uniquely solved using a specially designed well line protective device 34 which is installed in the tubing string 24 and forms an axial portion thereof, and is disposed within the rig floor/rotary table opening 18 as best illustrated in FIGS. 1 and 2. As will now be described, the device 34 laterally shields the longitudinal portions of well lines 28,30,32 disposed within the opening 18 from impact damage by the surface of the opening 18.
Protective device 34 includes a generally tubular metal first member 36 having an outer diameter D (see FIG. 3) greater than that of the tubing string 24, a pair of opposite reduced diameter end portions 38 threadingly connectable to axially facing segments of the tubing string 24, and circularly cross-sectioned central axial passage 40 opening outwardly through the end portions 38. For purposes later described herein, and as best illustrated in FIGS. 2A and 4, the first member 36 has an axially elongated exterior side surface recess 42 which opens outwardly through top and bottom ends 44,46 of the radially thickened longitudinally intermediate portion of the first member 36. Recess 42 has a generally planar inner side surface 48 along the vertical length of which three spaced apart semicircularly cross-sectioned indentations 50 extend, each of the indentations 50 being sized to receive a semicircular lateral half of a longitudinal portion of one of the well lines 28,30,32. Adjacent the outer side of the recess 42 (see FIG. 2A) are opposing recess side surfaces 52,54 that slope toward one another in a radially outward direction.
The well line protective device 34 also includes a vertically elongated second metal member 56 (see FIGS. 1 and 2A) having a cross-section permitting it to be slidingly and complementarily inserted in an axial direction into the first member recess 42, a generally planar inner side surface 48a in which three spaced apart semicircularly cross-sectioned indentations 50a are formed, an arcuate outer side surface 58, and a pair of oppositely sloped side surfaces 52a,54a extending between the surfaces 48a and 58. Like the indentations 50, the indentations 50a are each configured to complementarily receive a semicircular lateral half of a longitudinal portion of one of the well lines 28,30,32. The side surfaces 52a,54a have slope angles substantially identical to those of the first member recess side surfaces 52 and 54.
With the second member 56 separated from its associated first member 36 as shown in FIG. 2A, lateral halves of longitudinal portions of the well lines 28,30,32 are placed in the first member recess side surface indentations 50 as shown in FIG. 2. Next, the complementarily cross-sectioned second member 56 is axially slid into place within the recess 42 in a manner such that, as shown in FIG. 2, the second member indentations 50a complementarily receive semicircular lateral halves of the longitudinal well line portions received in the recess 42.
The inserted second member 56 substantially fills the entire recess area unoccupied by portions of the well lines 28,30 and 32, and laterally outwardly shields such well line portions, with the first and second member side surfaces 48,48a being in a closely contiguous, substantially parallel relationship. By comparing FIGS. 2 and 2A it can be seen that, with the second member 56 operatively inserted into the first member recess 42, the cooperative engagement of the oppositely sloped side surface pairs 52,54 and 52a,54a of the first and second members 36,56 prevent the lateral dislodgement of the second member 56 from the first member recess 42. As schematically shown in FIG. 1, suitable fastening members 60 are appropriately extended through the second member 56 into the first member 36 to releasably prevent axial dislodgement of the second member 56 from the first member recess 42. As can further be seen in FIG. 2, the arcuate second member outer side surface 56 forms with the outer side surface of the first member 36 a substantially circular outer side surface portion of the protective device 34.
With the protective device 34 in place within the rig floor/rotary table opening 18 as shown in FIG. 1, the device 34 very strongly prevents the longitudinal portions of the well lines 28,30,32 within such opening from impact damage by its peripheral surface brought about by wind and wave-created movement of the opening relative to the tubing string 24. Lateral impact loads on the inserted second protective device member 56 are simply transferred to the first protective device member 36 without deforming or otherwise damaging the well line portions extending through the assembled protective device 34. Protective device 34 is easy and relatively inexpensive to manufacture, may be rapidly installed in the tubing string 24, and is quite simple to protectively install around the longitudinal well line portions to be shielded from damage.
Referring now to the bottom portion of FIG. 1, another potential problem presented in floating offshore well apparatus such as the rig 10 is the possibility of gas leakage into the tubing/riser annulus 26 above the conventional annulus shutoff equipment (such as sealing rams and shearing rams) typically installed in the blowout preventer structure on the sea floor (not shown). The resulting gas flow up the annulus 26 (arising, for example, from a leak in the tubing string 24 above the safety shutoff equipment at the sea floor) is potentially hazardous from two standpoints. First, if the gas is a poisonous one such as hydrogen sulfide, it can come up through the open riser end 22 and put the rig crew at risk from the gas itself. Second, regardless of the kind of gas entering and traveling up the annulus 26, if the gas flow rate is sufficiently high the rig platform can lose buoyancy and sink. The conventional approach to gas leakage into the annulus 26 above the safety annulus shutoff equipment at the sea floor has been simply to evacuate the rig.
As schematically depicted in a bottom portion of FIG. 1, the present invention uniquely addresses and substantially solves this potential gas leakage problem by utilizing a well line protective device 34a disposed within an upper end portion of the riser 20 and positioned within a conventional sealing ram structure 62 supported on the riser 20 above a gas bypass conduit structure 64 communicated with the tubing/riser annulus 26 at a point below the sealing ram structure 62.
The well line protective device 34a is installed in the tubing string 24 and is identical to the previously described protective device 34 with the exception that it utilizes a different second member 56a (see FIG. 5). Second member 56a has a configuration identical to that of the previously described second member 56 but is formed entirely from a resilient material such as a suitable elastomeric material. Like its counterpart 56 the resilient second member 56a is axially inserted into the first member recess 42, to laterally outwardly shield the longitudinal portions of the well line members 28,30,32 passing through the protective device 34a, and is axially retained in the recess 42 by fastening members 60.
Ram structure 62, as mentioned above, is of a generally conventional construction and includes an opposed pair of semicircular ram members 66 which, in their solid line open position, face opposite exterior side portions of the protective device 34a and are outwardly withdrawn from the annulus 26. When a leakage of gas 68 upwardly through the annulus 26 is appropriately sensed, the ram members 66 are horizontally driven through a closure stroke, as indicated by the arrows 70 in FIGS. 1 and 5, to their closed position indicated in FIG. 5 and in phantom in FIG. 1. In such closed position the ram members 66 sealingly engage the exterior side surface of the protective device 34a and block off upward flow of the leaking gas 68 through the annulus 26 past the closed ram members.
The resilient second member 56a serves to protect the longitudinal portions of the well lines 28,30,32 extending through the protective device from the very large horizontal force of the ram members 66. Additionally, the ram forces serve to horizontally compress the second member 56a against the longitudinal portions of the well lines 28,30,32 to thereby form a seal around them and prevent upward gas flow around their peripheries.
With the annulus 26 sealingly blocked off in this manner, the gas 68 is forced to flow outwardly through the bypass conduit 64, as shown in FIG. 1 (instead of simply exiting the annulus 26 through the open top end 22 of the riser 20), for diversion to a location disposed a safe distance away from the rig.
In place of the all-elastomer second member 56a, a modified version 56b thereof (see FIG. 6) may be utilized. The modified second member 56b has a metal main body portion 72 with an elastomeric inner side portion 74 which, with the ram members 66 in their closed positions, is deformed and seals against the longitudinal portions of the well lines 28,30,32 passing through and laterally shielded within the first member passage 42.
While the protective devices 36,36a have been representatively illustrated as being used to laterally shield longitudinal portions of three well line members, it will be readily appreciated by those of skill in this particular art that it could be used to so shield a greater or lesser number of well line members if desired. For example, a larger or smaller number of well lines (depending on their lateral dimensions) could be shielded within the indicated first member recesses 42 if desired. Moreover, one or more additional exterior side surface recesses could be formed in the first member and used in conjunction with additional second members to shield a greater number of well line members. Finally, while the protective devices 36,36a have been representatively illustrated as being incorporated in an offshore well system, it will be readily appreciated by those of skill in this particular art that they could used in other types of well applications as well.
The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.