SYSTEM FOR ELIMINATING AND REMOVING HYDRATES AND OTHER BLOCKAGES IN UNDERSEA LINES

Abstract

The present invention addresses to a system for removing hydrates and other scales in subsea pipes in oil production fields. More specifically, the present invention addresses to a system for fighting and removing hydrates and other scales comprising independent traction modules, equipped with load cells that act by controlling other traction modules, wherein said traction modules are interconnected intercalated with armored cable sections. The system of the present invention is applied in rigid or flexible pipes that present restrictions or blocks to the flow.

Description

FIELD OF THE INVENTION

The present invention addresses to a system for removing hydrates and other blocks in subsea pipes in oil production fields. More specifically, the present invention addresses to a system for fighting and removing hydrates and other blocks comprising independent traction modules, equipped with load cells that act by controlling the traction modules, wherein said traction modules are intercalatedly interconnected with sections of armored steel cable (steel cable with facilities for the transport of electrical and/or hydraulic power, in addition to, optionally, a circuit for the circulation of fluids, aiming at making energy available for their locomotion, as well as the driving of tools that this may come to load). The system of the present invention is applied in rigid or flexible tubes that present restrictions or blocks to the flow.

DESCRIPTION OF THE STATE OF THE ART

In the oil and gas exploration field, obstructions caused by hydrates or scales in subsea pipes are frequently observed. There are tools for accessing and removing these obstructions, but they do not have great reach, especially in the horizontal part of the tubes, since it only relies on gravity for its positioning or limitations in relation to reach, due to friction between the cable and the wall of such tubes.

The formation of hydrate generates many losses for the exploration and production of oil and/or gas, restricting its flow rate and may even cause the obstruction of production or service lines. Researches and new developments have emerged to minimize the loss of production in oil wells.

It is not possible to use hydrate inhibitors in production or service lines after the block occurs, since hydraulic shims and columns of liquids are formed that prevent the injection of these chemicals at the necessary points. The hydrate formation is caused by high pressures and low temperatures, typical conditions in oil wells at great depths.

Mechanical methods of scale removal are carried out through the use of PIGs, but not all lines are “piggable”, requiring a specific constructability of equipment and even the efficiency of these devices is limited. There is still the possibility that the PIG will generate a block if it drags a lot of material with the same. In addition, the use of PIG requires that there is flow for its displacement.

Another method used, the coiled tube, has difficulties due to the low capacity in relation to the reach, mainly in the horizontal part of the production tubes, since it only relies on gravity for its positioning. Some pieces of equipment with their own traction are used in wells, but they are not suitable for pipes due to sharp bends, inflection points and the consequent friction, generating high loads to pull the power supply cable, as well as the load on this cable for the recovery of the traction device.

There are some systems that use two units, that is, a tractor module and an inspection module. As a rule, the tractor device is not driven to return, as it can “settle” when it “runs over” the cable that supplies energy thereto, increasing its entrapment inside the tube.

Pieces of equipment with its own means of locomotion are used, but they are not suitable for tubes comprising sharp bends, inflection points and high friction caused by the power cables that these pieces of equipment make use of, providing high load to pull such a supply cable energy, as well as high load on said cable at the time of equipment recovery, in case it is pulled back.

The tools currently used to fight hydrate and other obstructions are:

• • Coiled tubing—a tube positioned on a spool, and inserted from the top of a riser, where it accesses the suspended section of flexible or rigid tubes and wells in its vertical section and at the beginning of the horizontalization curvature. This device acts by gravity itself and the main limiting factor is the buckling of this tube, due to its high slenderness.
  • Traction tools: used in the vertical, directional and horizontal section of wells, typically structures with a large radius of curvature, but without, or almost without, inflection points.

Document WO2008111844A1 refers to a steel cable tractor. More particularly, it refers to a steel cable tractor comprising at least one drive wheel positioned on a shifting mechanism connected to the steel cable tractor, in which the shifting mechanism is arranged so as to maintain the drive wheel in a stressed manner against a well or tube wall. The shifting mechanism is at least rotatable or movable between a first position, in which the drive wheel rests against the well wall on one side of the tractor, and a second position, in which the drive wheel rests against the well wall on the opposite side. In this sense, the steel cable tractor applies a tension load that allows pulling the cable that it carries, moving through the well. Steel cable tractors have taken on considerable application in, for example, equipment and maintenance work on oil wells. Many steel cable tractors are supplied with drive wheels that are tilting. Often the attached cable is used to pull the steel cable tractor out of the well.

The invention PI0005931-3A addresses to an inspection PIG. These pieces of equipment designed for extensive lines are mainly used in subsea or underground lines. The operating mechanism is through high pressure fluids that drive the PIG movement. The action of the pressure fluid is on the annular cup positioned either at the front or back part, and is responsible for adjusting to the diameter of the piping and promoting a certain sealing. Accordingly, the fluid that drives the pig acts on the annular cup. Accordingly, moved by the flowing fluid, this mechanism cannot work well in clogged tubes.

Another type of PIG, based on a single body of polyurethane or foam-based, and which are used in situations of lines with different accessories, are not sufficient for cleaning some types of scales, especially hydrates due to the hardness of the scaling.

Intermediate tractor devices are not adopted due to the difficulty in synchronism between such devices, among other reasons.

FIG. 10 shows an example of the coiled tubing system, which represents an embodiment of the state of the art, but which does not have a tractor at the end of the cable/rod/tube. This is only applicable in vertical or horizontal sections with short reach, since the cable/rod/tube with eventual tools descends by gravity. However, the drawing also illustrates what the winch drum can be, which takes the armored cable intercalated with traction elements, proposed in this document.

Thus, there is currently no tool or means that is applied to the static section of pipes, especially the flexible ones that have more accentuated curvature characteristics. Furthermore, the static sections are the most susceptible to problems that may require such interventions, positioning themselves on the seabed, typically far from the inlet end of such tools.

The present invention solves a problem that makes it impossible to move tractor devices in the reverse direction: this problem is the risk of the tractor overlapping the electrical supply and control cable to which the device is coupled. This is solved with a control system associated with measurements performed by load cells installed at the rear end of the tractor module (21), or at both ends, when applied to intermediate modules (20). Assuring a minimum value of tension in each cell, the traction modules can act in a synchronized way with the cable retraction, increasing or decreasing the forward or backward speed of each module, ensuring that the cable always remains tensioned.

BRIEF DESCRIPTION OF THE INVENTION

The present invention refers to a system for fighting and removing hydrates and other scales comprising independent traction modules arranged in series, and each traction module is coupled to the next traction module by an armored cable segment.

The traction modules (tractors), modules responsible for pulling the cable segments, are capable of not only being boosters or acting for traction, but also as if they were modules for measuring loads. In this way, the values of stresses caused by axial loads in the cables are not cumulative in a single cable. Accordingly, it became possible to increase the loading concentrated in a single module, and therefore, making it more effective to reach the points of interest for scale removal.

This has an advantage over traditional PIGs and other technologies, as large tensile loads are not required in cables or systems that use booster fluids with very high pressures. In addition, the cable that interconnects the tractor system contains within the same an umbilical for electrical and hydraulic supply, fluid circulation and cables for collecting information from sensors.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be described in more detail below with reference to the attached drawings, which in a non-limiting way of the inventive scope, represent a preferred embodiment. Thus, there are:

FIG. 1 illustrates the system of the present invention positioned within a flexible tube, with a reach associated with the number of used segments;

FIG. 2 illustrates a top view of the socket for interconnecting between armored cable segments of the present invention;

FIG. 3 illustrates a side view of the socket for interconnecting between armored cable segments of the present invention;

FIG. 4 illustrates a side view of the rolling wheel used in the coupling between sockets of the present invention;

FIG. 5 illustrates a top view of the connection between two sockets that interconnect two sections of armored cable comprising a rolling according to the present invention;

FIG. 6 illustrates a side view of the connection between two sockets comprising a rolling according to the present invention;

FIG. 7 illustrates the angle lag that must ensure that rolling wheels touch the inner surface of the tube, ensuring a reduction in the observed friction;

FIG. 8 illustrates a side view of an alternative configuration to the use of wheels with sockets shown in FIGS. 2 to 6, where the set of wheels snap together and are attached to the armored cable, in a split system;

FIG. 9 illustrates a top view of an alternative configuration, using the wheels, in the split system;

FIG. 10 illustrates the conventional configuration, using the coiled tubing, a technology that is limited to wells or applications with short reach.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a system for fighting and removing hydrates comprising independent traction modules (20), arranged in series, and each traction module (20) is coupled to another next traction module (20), by an armored cable segment (10), in addition to the end traction module (21) located at the end of the assembly.

The traction modules (20) and end traction module (21) of the present invention, also known as tractors, are preferably of the active type, that is, they comprise means of auto-locomotion, with electric or hydraulic drive. Furthermore, the traction module located at the end (21) comprises means for positioning tools to fight and remove hydrates and other blocks such as scale deposition. Further, the traction modules (20) are equipped with load cells that comprise the electronic devices, and sensors whose function is to control and supply the traction (20) and the end (21) modules.

The armored cable segments (10) are provided with tubings for the transport of fluids (hydraulic and chemical products) along their length, as well as an electrical supply containing a plurality of conductor wires and for data transport, in the same way as the traction (20) and end (21) modules themselves, which allows the (electrical and hydraulic) transmission to the next segment.

The armored cable segments (10) have, in their core, a layer containing a plurality of steel cables to meet the mechanical traction. Furthermore, the armored cable segments (10) comprise an outer sheath, preferably of nylon or Teflon, and comprise a preferred length of up to five hundred meters; however, this length may vary due to different conditions, such as the friction force per meter for a typical tube configuration, internal diameter, internal material and geometry, radii of curvature, average number of inflection points per km, and total distance to be reached.

The tractors or also traction modules (20) are intercalatedly interconnected with sections consisting of segments of steel armored cable (10), and are further associated with the steel cable winch (30), so that the loads are always of tension, preventing damage to the set of armored cables (10) and traction modules (20).

The armored cable segments (10), according to the present invention, provide distances comprising approximately between 2 and 20 meters in length (not limited to that), where, preferably, each segment comprises 2 to 20 meters of cable, and are coupled to the other segments through sockets (12) attached at their ends, as shown in FIGS. 2 and 3.

FIGS. 3 and 5 show the sockets (12), which are structures comprising a “U”-shaped support, comprising two legs (13) with a hole (15) in each leg (13) of the “U”. The coupling between two sockets comprises positioning the sockets (12) so that each leg (13) of one socket (12) is between the two legs (13) of the other socket (12). The coupling further comprises the introduction of a rolling wheel (14), according to (FIG. 4), comprising a hole (16), so that the holes (15) of all the legs (13) of the two sockets (12), plus the hole (16) of the wheel (14) are aligned. The coupling between two sockets further comprises the introduction of a locking pin (17) in the holes of the sockets (12) and the wheel (14), functioning as a pivot axle between the sockets and an axle for the wheel (14).

The sockets (12) of both ends of a sub-segment of the segment (10) and, consequently, the wheels (14) must have a relative positioning with misalignment, or lag, of about 45° or about of 90° to each other, as shown in FIG. 7. This lag allows the armored cable segment (10) not to settle in such a way as to impair the operation of said rolling (14).

Each socket (12) must have (hydraulic and chemical) fluid and electricity transmission facility, of the swivel type, in the same way as between the socket (12) of the end of the armored cable segment (10) that connects to the traction module (20).

The armored cable segments (10), between a traction module (20) and another, can reach lengths of up to 500 meters; therefore, the sockets (12) must resist high traction tensions. In this way, they are preferably made of a material with sufficient strength to support the weight of at least three kilometers of such a set of cables. Said sockets (12) provide the connection between the armored cable segments (10) and a rolling (14), using locking pins and nuts. The sockets (12) at both ends must have a misalignment, or offset, of about 45° or about of 90°, depending on the diameter of the rolling (14) and the length of each sub-segment. This lag allows the armored cable segment (10) not to settle in a way that harms the operation of said rolling (14).

Additionally, the armored cable segments (10) can comprise steel wires in different assembly directions, thus preventing twists from causing said settling of the armored cable (10), even with the use of said socket lag (12).

Alternatively, the need for sockets (12) with the aforementioned relative positions can be replaced by the alternative configuration, shown in FIGS. 8 and 9, that is, an alternative configuration consisting of split devices (22) provided with rolling wheels (24). Such devices comprise a split structure, which grips the armored cable (10), avoiding the need for sub-segmentation of said cable. In this case, there are no sub-segments, there is only one pair of sockets (12), one at each end of each armored cable segment (10), these maintaining the need of having swivels in each of the sockets (12) , to perform the interface between each end of the armored cable segment (10) and its respective module (20).

This split device (22) is secured by screws and nuts (23) on each side of the axle of the rolling wheels (24), containing two wheels on the same axle. There is no coupling between sub-segments, since there are no discontinuities in the armored cable segment (10). The distance between each of the split devices (22), in this case, can be adjusted as a function of the expected loads related to friction.

The present invention further enables the use of tractor devices of the state of the art, as long as they undergo miniaturization, in order to allow their use in subsea flexible tubes, passing in more severe radii of curvature, incorporating great value and flexibility of use to these pieces of equipment. FIG. 10 shows an example of the coiled tubing system, which represents an embodiment of the state of the art, but which does not have a tractor at the end of the cable. This is only applicable in vertical or horizontal sections with short reach, since the cable with eventual tools descends by gravity. In the same figure, there is a structure that represents a device that isolates the interior of the tube from the external environment, acting as a BOP—Blow Out Preventor (40) and that needs to be adapted to the passage of the traction tool (each of its segments), in addition to the wheel devices.

The BOP (40), typically used in drilling and well intervention, must have shear gate valves, so that they allow the cable to be cut, in case this is necessary to avoid uncontrolled fluid return.

The same must also be able to divert such flow, if any, to a safe place (vessel, vent, etc.).

The present invention solves a problem that makes it impossible to move tractor devices in the reverse direction; this problem is the risk of the tractor “running over” the electrical supply and control cable to which the device is coupled. This is solved with a control system associated with load cell measurements installed at the rear end of the most advanced tractor module, or at both ends, when applied to intermediate modules. Assuring a minimum value of traction in each cell, the traction modules can act synchronously both in the advance and in the retraction of the cable.

The system according to the present invention minimizes the problem of friction present in the solutions of the state of the art using armored steel cable—steel cable containing hydraulic hose and/or electric cable to feed the traction equipment and coupled accessories, at the same time that allows the segmentation of the cable so that it can be pulled by several modules that, activated synchronously, divide the loads generated by the friction between the cable and the internal walls of the tube.

The application according to the present invention is directed to rigid or flexible tubes that present restrictions or blocks to the flow, for their clearing.

The associated use of distributed controlled traction and friction reducers in the armored cables (10) reduces the loads to tolerable levels, allowing a reach of several kilometers from the platform where the tube is interconnected. With this, it is possible to fight blocks caused by hydrate formation or deposition of scales, allowing tools to access the pipe at points with such blocks or restrictions, said tools consisting of, for example, pieces of equipment for mechanical removal, application/circulation of chemicals, local heating generation, etc., coupled to the module positioned at the end of the first cable segment.

With the reduction of scaling, there will be a reduction in the head loss to the flow during the production of wells, increasing their production potential and, in the case of hydrates, which usually restrict production completely, the return to production in much less time, when compared to conventionally adopted methodologies, for example, the use of probes associated with the depressurization of the pipe.

The active intervention (enabled with the invention, for long distances) tends to accelerate the solution of the problem, not being limited to passive solutions (typically adopted with the use of intervention probes), where one literally waits for the “ice to melt”.

Thus, with the use of the system object of the present invention, an order of magnitude as to savings of approximately 90% is estimated, justifying its prompt adoption.

It should be noted that, although the present invention has been described in relation to the attached drawings, it may undergo slight changes, but not departing from the presented embodiment.

Claims

1- A SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS, characterized in that it comprises independent traction modules (20) arranged in series, and each traction module (20) is coupled to the next traction module (20) by an armored cable segment (10), sockets (12) or a split device (22); and a BOP device (40).

2- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 1, characterized in that the traction modules (20) and the end (21) comprises means of auto-locomotion that are electrically or hydraulically driven.

3- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 1, characterized in that the traction modules comprise means for positioning tools to fight and remove hydrates and deposition of scales.

4- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 1, characterized in that the means for positioning hydrate fighting tools is located in the end traction module (21).

5- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 1, characterized in that the traction (20) and end (21) modules are equipped with load cells that comprise the electronic devices and sensors.

6- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 1, characterized in that the armored cable segments (10) comprise segments preferably comprising 20 meters in length, but not limited to this length, and are provided with means for the transport of fluids, power supply and data transport along its length.

7- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 1, characterized in that the armored cable segments (10) preferably comprise nylon or Teflon coating; and may reach 500 meters between each traction module (20) or (20) and (21).

8- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 7, characterized in that the segments comprise sockets (12) at their ends for coupling between each segment.

9- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 8, characterized in that the sockets (12) comprise a “U”-shape support, comprising two legs (13) with a hole (15) in each leg (13) of the “U”.

10- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 9, characterized in that the coupling between armored cable segments (10) comprises the positioning of the sockets (12) so that each leg (13) of a socket (12) is located between the two legs (13) of the other socket (12), which will have channels forming a “swivel” rotating link that will allow the transmission of hydraulic pressure and electrical signals.

11- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 10, characterized in that the coupling between armored cable segments (10) comprises the introduction of a rolling wheel (14) comprising a hole (16), of so that the holes (15) of all the legs (13) of the two sockets (12) plus the hole (16) of the wheel (14) are aligned.

12- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 11, characterized in that the coupling between armored cable segments (10) comprises the introduction of a locking pin (17) in the holes (15) of the sockets (12) and in the holes (16) of the wheel (14), functioning as a pivot axle between the sockets and an axle for the wheel (14).

13- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 12, characterized in that the sockets (12) of both ends of a sub-segment of each armored cable segment (10) have an angle of 90° between such sockets and their subsequent socket.

14- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claims 1 to 7, characterized in that the split device (22) has the cylindrical body adjustable to the armored cable (10) and with a locking system by screws and nuts (23).

15- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 14, characterized in that the split device (22) contains at least 2 wheels interconnected to the same axle.

16- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 15, characterized in that the sockets (12) or the split devices (22) are arranged in a misaligned manner in relation to each other at any angle, preferably at the angles of 45° or 90°.

17- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claims 1 to 16, characterized in that there is an electronic speed control system of the wheels present in the traction (20) and the end (21) modules in order to ensure the existence of traction loads in the armored cable segments (10).