Patent Application
20120241165
1. Technical Field
This invention consists of thermal insulation for pipes of steel of a drill pipe riser, also denominated as DPR, for the exploitation of petroleum in subsea wells.
2. History of Related Art
As it is generally known, a drill pipe riser is made up of several lengths of pipes threaded together at their respective ends, to be used to drill an oil well, as well as for long-term production test of wells (lasting five to nine months) in order to measure the flowrate of that well or if the well is economically viable. The long-term production test also allows the pre-production of the well.
After the conclusion of the tests, the drill pipe riser is removed and the final flexible pipe risers are installed.
The pipes of the drill pipe riser are made of steel and, considering the low temperatures at great depths, said pipes must be thermally insulated, in order to prevent heat transfer from the petroleum to the seawater during its passage from the sea bottom to the surface. If there is no thermal insulation, the petroleum becomes very viscous substantially reducing its flow rate.
The thermal insulation of the prior art technique for the drill pipe riser is applied to the pipes of the column by means of a hot thermoplastic wrapping, in a spiral manner, on each pipe of the drill pipe riser or by means of a spray gun.
One of the inconvenient aspects of insulations from the prior art technique is that the thermoplastic is applied in such a way to the pipe that water cannot pass between the pipe and the internal surface of the thermoplastic. Thus, due to the high subsea pressures to which the insulation is subject, the entry of water is forced between the insulation and the joint, forming a type of water pocket under pressure. Thus, when the drill pipe riser is raised to the surface, a phenomenon known as a “bursts” (embolism),” in other words, the water contained under pressure in the pocket, breaks through the insulation in many places.
Another shortcoming of the prior art thermal insulation is the fact that the insulation of the joint coupling of two pipes is done using two half chutes which are bound to each other by several straps. This insulation takes a long time and is complicated, resulting in considerably higher costs and, frequently as well, the “bursting” phenomenon occurs, damaging the insulation.
The objectives of the present invention are the production of a thermal insulation for a drill pipe riser that avoids this “bursting” phenomenon and that substantially reduces the costs of insulation and installation of the riser.
This objective is achieved by a thermal insulation of the pipes of the drill pipe riser for subsea petroleum production, wherein it includes at least one layer of thermal insulation applied around a pipe, so that between the pipe and the thermal insulation there is a space where sea water penetrates. The objective is also achieved by a thermal insulation which comprises several layers of thermal insulation applied around a pipe, so that between the first layer and the pipe and between each two adjacent layers there are spaces where sea water penetrates.
Thus, one of the advantages of the thermal insulation according to the invention is the fact that the spaces allow the penetration of water when the pipe is under water and the drainage of water as the drill pipe riser is hoisted to the surface. In this manner, bursting and consequent damage to the insulation is avoided.
Another advantage of the invention is that the water that penetrates into these spaces forms an insulating film that increases the efficacy of the thermal insulation even more.
The objective of the invention is also achieved by means of a thermal insulation system for joint couplings of a drill pipe riser for subsea petroleum production, comprising a tubular segment that circumferentially envelops the region of the joint coupling of a first pipe with a second pipe of a thermally insulated drill pipe riser, and extends, preferably, beyond the ends of the thermal insulation of said pipes, wherein between said tubular segment and the pipes there is a space where sea water penetrates and wherein a course stop keeps the tubular segment in its position, and wherein the tubular segment is vertically displaceable, in a telescopic manner, from the first pipe, located vertically above the second pipe, until it is located in the region of the joint coupling, and wherein the course stop limits the displacement of the tubular segment.
Thus, one other advantage of the invention is the fact that the thermal insulation of the joint coupling of two pipes avoids “bursting” and is done much more quickly, substantially reducing installation costs.
The invention will be described in more detail below, based on the attached figures, as examples:
FIG. 1—view of a pipe that has been thermally insulated according to the invention;
FIG. 2—cross section view of pipe of
FIG. 3—enlarged view of the cross section of
FIG. 4—cross section view of a second embodiment of the thermal insulation according to the invention;
FIG. 5—cross section view of a third embodiment of the thermal insulation according to the invention;
FIG. 6—cross section view of a fourth embodiment of the thermal insulation according to the invention;
FIG. 7—longitudinal sectional view of the tubular segment according to the invention for thermal insulation of the joint couplings;
FIG. 8—view of the thermal insulation system for joint couplings, according to the invention.
Embodiment(s) of the invention will now be described more fully with reference to the accompanying Drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment(s) set forth herein. The invention should only be considered limited by the claims as they now exist and the equivalents thereof.
The first layer 6 has a longitudinal groove 9 along its entire thickness and length, which facilitates the placement of this layer 6 on pipe 1. The second layer 7 is complete (without groove) and both layers 6 and 7 are installed by extrusion, preferably. For example, the layers are cold laid (pushed), on one of the joint's ends, in other words, first the first layer 6 is laid, when the groove 9 is opened during its placement and, following that, the second layer 7 is laid on the first layer 6. The thermal insulation according to the invention may consist of several layers of thermal insulation.
In one other embodiment (not shown in the figures), the thermal insulation according to the invention may extend from the first end of pipe 3, the female end, to the second end of the pipe 4, the male end, completely insulating the pipe, longitudinally and around its circumference. In this case, in the regions of the end of pipe 1, where the diameter is greater, a length of insulation may be placed with an internal diameter greater than that of the rest of the pipe. With this alternative for thermal insulation of pipe 1, it is not necessary to use a tubular segment to insulate the joint coupling between the two pipes 1.
The figure shows a joint coupling 16 between a first pipe or upper pipe 17 and a second pipe, or lower pipe 18. Both pipes have the thermal insulation 2 according to the invention. One can see in the figure that the tubular segment 15 is located in an initial position, surrounding the first pipe 17, before installation in the region of the joint coupling 16. Next, this tubular segment 15 is displaced telescopically downwards, as arrow 19 shows, until it reaches its final position enclosing joint coupling 16. In the final position, the tubular segment 15, shown in dashed lines, extends preferably beyond the ends of thermal insulations 2 of said pipes 17 and 18, and forms a space 20 with pipes 17 and 18, where water penetrates. Said space 20 avoids the occurrence of bursting, in other words, the space 20 allows the entry of sea water due to the pressure of said sea water, and allows its drainage as the drill pipe riser is hoisted to the platform.
One can also see on the figure an upper sleeve 21 and a lower sleeve 22, which are attached respectively to pipes 17 and 18, for example by means of gluing and serve to guide the tubular segment 15 when it slides down to the region of joint coupling 16. Sleeves 21 and 22 also serve to create an obstruction to the drainage of water from space 20 between tubular segment 15 and pipes 17 and 18 of the drill pipe riser. These sleeves 21 and 22 have a slight clearance in relation to the internal surface of the tubular segment 15, which allows for the entry of sea water in the space 20, but avoids a free water flow, so that the water contained in space 20 remains confined during the operation, creating a thin layer of thermal insulation and, consequently, increasing insulating capacity of the tubular segment 15.
As the drill pipe riser is hoisted to the surface of the sea, the water drains from space 20 through the clearance between the tubular segment 15 and sleeves 21 and 22, thus avoiding the bursting.
One can also see in the figure that the thermal insulation system according to the invention comprises a course stop that prevents downwards movement of tubular segment 15. In the embodiment shown in
The course stop can also consist of a disk, for example, (not shown in the figures) attached to the lower pipe 18, wherein the perimeter of said disk acts as a dead stop for limiting the displacement of the tubular segment 15 in a manner similar to dead stop 23 as described above.
In another embodiment, the course stop can consist of at least one bolt 25 (shown by dashed lines in
In one other embodiment of the system according to the invention (not shown in the figures), the sleeves are not necessary. In this embodiment, the wall thickness of tubular segment 15 should be greater, so that the clearance between the thermal insulation of the pipes 17 and 18 and the internal wall of tubular segment 15 is very narrow, in order to prevent a free flow of water during the operation of the drill pipe riser. Besides this, given the narrow clearance, the thermal insulation 2 of the upper pipe 17 acts as a guide of the tubular segment 15 during its downwards displacement until the joint coupling 16.
The thermal insulation according to the invention may be composed of any insulating material that is resistant to sea water. One may use, for example, a plastic, such as polypropylene, polyethylene, polystyrene, nylon, acrylics, or even rubber.
Besides the embodiments presented above, the same inventive concept may be applied to other alternatives or possibilities for the use of the invention. For example, the invention may be used in other subsea areas regardless of salinity or maritime currents, such as, for example, in rivers, bays, lakes and canals.
Therefore, it should be understood that this invention may be interpreted in a broad manner, wherein its scope of protection is determined by the terms of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| PI 1101090-8 | Mar 2011 | BR | national |
