Abstract:
The invention relates to a fracturing tube system ( 1 ) for introducing into a borehole in order to carry out a hydraulic and/or pneumatic fracturing process, comprising a plurality of tube lines ( 10 ). The fracturing tube system is to be designed such that it can be produced in a simpler and more economical manner and such that a variable total length of the fracturing tube system can be introduced into a borehole with little effort. This is achieved in that the fracturing tube system ( 1 ) comprises at least one traction cable ( 11 ), multiple coupling devices ( 12 ) which can be removably attached to the at least one traction cable ( 11 ), and multiple tube sections ( 100 ) which are separate from one another and which can be coupled to the coupling devices ( 12 ) in a pressure-tight manner and thus form the tube lines ( 10 ) as a whole. A pressure-tight releasable connection of the tube sections ( 100 ) to feedthroughs ( 120 ) of the coupling device ( 12 ) can be achieved so that fluid can be conducted from one tube section ( 100 ) into a subsequent tube section ( 100 ) through the feedthrough in the coupling device ( 12 ) in a tube-free manner.

Description:
TECHNICAL FIELD 
       [0001]    The present invention describes a fracturing tube system comprising a plurality of tube lines for being introduced into a bore hole in order to carry out a hydraulic and/or pneumatic fracturing process, as well as the utilization of at least one traction cable, multiple coupling devices that can be removably attached to the at least one traction cable and multiple separate tube sections in the form of corrugated metal tubing with a braiding, which can be coupled to the coupling devices in a pressure-tight fashion and collectively form the tube lines, for assembling a fracturing tube system. 
       PRIOR ART 
       [0002]    Hydraulic fracturing (hydraulic fracturing) and/or pneumatic fracturing, which is generally also referred to as fracking, is used for extracting hydrocarbons, natural gas or crude oil from corresponding subterranean natural gas or oil formations. Among other things, hydraulic and/or pneumatic fracturing also makes it possible to reactivate abandoned natural gas or oil formations and to thereby extract residual amounts of liquid and gaseous fossil fuels that were previously inaccessible, wherein this process is also referred to as intervention. 
         [0003]    Natural gas or oil formations usually are subterraneously fractured with the aid of a fracturing fluid in order to create artificial flow channels for the hydrocarbons to be extracted and to thereby simplify the process of pumping off the hydrocarbons. To this end, a multi-lumen tubing has to be purposefully lowered into an existing bore hole for the hydraulic and/or pneumatic fracturing process, wherein this is also referred to as coiled tubing. The multi-lumen tubing is unwound from a drum on-site with a suitable device and lowered into the bore hole to a depth between a few meters and a few kilometers. In this case, the fixed length of the multi-lumen tubing has to be adapted to the desired lowering depth or bore hole depth, respectively. A corresponding system for carrying out hydraulic and/or pneumatic fracturing processes is illustrated in  FIG. 6 . 
         [0004]    Subsequently, the fracturing fluid is hydraulically pumped into the bore hole in a controlled fashion by means of tube lines of the multi-lumen tubing. Since the fracturing fluid not only contains water, but also supporting particles and/or additives that preserve the fractures being produced, the enlarged flow channels leading to the bore hole remain open such that an increased amount of hydrocarbons can be pumped off. 
         [0005]    Nowadays, preassembled multi-lumen tubing, which comprises a plurality of prefabricated tube lines in the form of metal tubes that typically have diameters between one inch and 3.25 inches, are used for hydraulic and/or pneumatic fracturing processes. The tube lines are completely encased in a plastic covering and form a flexible, compact tube line cluster. The thusly realized multi-lumen tubing is protected from external influences by the plastic covering, as well as an optional covering of steel cables and another optional plastic covering, wherein the individual tube lines are clustered in an encapsulated fashion at a distance from one another and enclosed by plastic. Such compact and integrally designed multi-lumen tubing can be introduced into a bore hole and is designed for being vertically and horizontally advanced therein. 
         [0006]    A preassembled multi-lumen tubing according to the prior art is illustrated in  FIG. 7  in the form of a fracturing tube system. In this case, four tube lines with an inside diameter of ¾ inch are enclosed by a plastic covering, as well as two rows of steel cables extending parallel to the circumference of the multi-lumen tubing, wherein an additional plastic covering encloses the two rows of steel cables. 
         [0007]    The individual tube lines serve for pumping in or pumping out fracturing fluids and/or for supplying supporting particles and/or additives, as well as for pumping off hydrocarbons. Since an electronically controlled pump device or control device (so-called packer) usually is subterraneously arranged on the multi-lumen tubing, this multi-lumen tubing also features optional electrical wiring that is likewise encased in the plastic covering along the entire length of the preassembled multi-lumen tubing. The fracturing tube system is manufactured with a constant outside diameter and a fixed length and wound on a drum. Since pressures up to 200 bar and temperatures within the bore hole of a few hundred degrees Celsius occur during hydraulic fracturing, the individual tube lines are realized in the form of metal tubes that are able to withstand these conditions. 
         [0008]    The manufacture of preassembled multi-lumen tubing known from the prior art is elaborate and expensive. The individual tube lines in the form of metal tubes have to be encased in the plastic covering at a distance from one another over the entire desired length of the multi-lumen tubing and the steel cable-reinforced outer covering also has to be arranged over the entire length of the multi-lumen tubing such that the preassembled fracturing tube system can be wound up on a drum in one piece for its transport and intended use. 
         [0009]    During the intended use of the fracturing tube system, this drum, which may have an enormous mass depending on the overall length of the wound-up fracturing tube system, has to be unwound in an exactly controlled fashion by means of a suitable device in order to introduce the fracturing tube system into the bore hole in a controlled fashion. 
       DISCLOSURE OF THE INVENTION 
       [0010]    The present invention is based on the objective of developing a fracturing tube system that can be manufactured in a simpler and more cost-efficient fashion, as well as introduced into a bore hole with a variable overall length and with reduced effort. 
         [0011]    The present fracturing tube system no longer has to be supplied in a preassembled fashion with a given overall length, but rather can be modularly assembled and therefore have a variable overall length such that it no longer has to be elaborately wound up on a drum in one piece. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A preferred exemplary embodiment of the object of the invention is described in greater detail below with reference to the attached drawings. 
           [0013]      FIG. 1  shows a schematic front view of a fracturing tube system with several tube lines that are composed of several tube sections and coupled to two coupling devices, wherein the entire fracturing tube system comprises a single traction cable, whereas 
           [0014]      FIG. 2  shows a partially sectioned view of a potential coupling device, in which yet uncoupled tube sections are indicated to both sides of the coupling device. 
           [0015]      FIG. 3  shows a partially sectioned view of a tube section, tube coupling means and device coupling means prior to the coupling process. 
           [0016]      FIG. 4 a    shows a sectioned view of a coupling device whereas 
           [0017]      FIG. 4 b    shows a side view of the coupling device. 
           [0018]      FIG. 5  shows a sectioned top view of a coupling device with inserted traction cable, but without tube sections flanged thereon, wherein the traction cable is not yet fastened in the cable leadthrough. 
           [0019]      FIG. 6  shows a schematic top view of a hydraulic and/or pneumatic fracturing system according to the prior art, in which a fracturing tube system is lowered into a bore hole, whereas 
           [0020]      FIG. 7  shows a sectional view of a fracturing tube system according to the prior art in the form of a multi-lumen tubing. 
       
    
    
     DESCRIPTION 
       [0021]    The fracturing tube system  1  presented herein comprises a plurality of tube lines  10  that can be introduced into a not-shown bore hole by means of a traction cable  11 . The tube lines  10  are arranged separately and spaced apart from one another, wherein said tube lines are composed of a plurality of separate tube sections  100  that are coupled to a plurality of coupling devices  12 . The tube sections  100  are provided with tube coupling means  101  that can be functionally connected to device coupling means  125  such that a pressure-tight separable connection between the tube sections  100  and feedthroughs  120  of the coupling device  12  can be produced and fluid can be conveyed in a tubeless fashion from one tube section  100  into a following tube section  100  through the feedthrough  120  in the coupling device  12 .  FIG. 1 or 2  respectively shows that the feedthrough  120  is the space in the coupling device  12 , through which the fluid flows. After the tube sections  100  have been coupled to the feedthroughs  120  of the coupling device  12 , a direct pressure-tight passage is created from the interior of each tube section  100  through the feedthroughs  120 . In this way, fracking fluids can be conveyed from outside the bore hole through the entire modular tube line  10  until they reach an outlet at the base of the bore hole. The arrow in  FIG. 1  indicates the direction, in which the fracturing tube system  1  is introduced. 
         [0022]    The tube sections  100  are held on the coupling devices  12  such that the respective tube sections  100  or tube lines  10  and the coupling devices  12  are held by the traction cable  11 . The preferably single traction cable  11  extending over the entire length of the fracturing tube system  1  is respectively routed through a cable feedthrough  121  in or on each coupling device  12  and removably attached to the coupling device  12  at this location. The overall length of the fracturing tube system  1  can be easily adapted. 
         [0023]    Additional tube sections  100  with section lengths I can be respectively coupled to additional coupling devices  12  as needed and connected such that the individual tube lines  10  are extended, wherein the length of the traction cable  11  also has to be adapted. Since the transport and the costs of a traction cable  11  are respectively not elaborate or expensive, a sufficiently long traction cable  11  can be chosen before lowering of the modularly designed fracturing tube system  1  begins. This traction cable  11  is unwound from a roll and respectively attached to each coupling device  12 . 
         [0024]    Corrugated metal tubing is used for the tube sections  100 . The corrugated metal tubing is made of steel, preferably of high-grade steel, and therefore extremely resistant to corrosion, wherein this corrugated metal tubing can withstand pressures up to a few hundred bar and temperatures up to 600° C. Consequently, corrugated metal tubing of this type is suitable for hydraulic and/or pneumatic fracturing processes, during which pressures up to 200 bar and occasional temperatures in excess of 200° C. occur. Increased fatigue strength is achieved due to the corrugation of the corrugated metal tubing. Corrugated metal tubing can be used for conveying liquid or gaseous mediums, as well as pumpable solids that are frequently added to the fracturing fluid as an additive. 
         [0025]    In order to provide sufficient mechanical protection for the tube sections  100 , it is advantageous to provide the tube sections  100  with a braiding  1000 . Although it was determined that a single braiding  1000  delivers adequate results during the utilization of the fracturing tube system  1 , it is preferred to respectively use a two or more braidings  1000  for strength reasons. The arrangement of one or multiple braidings  1000  increases the bursting pressure of the tube sections  100  and therefore of the entire tube lines  10 . The braiding  1000  consists of high-grade steel wire or galvanized steel wire and is directly braided on the circumferential surface of the tube sections  100  of corrugated metal tubing. Braided tube sections  100  of this type are commercially available. 
         [0026]    In this case, the tube coupling means  101  on both ends of the tube sections  100  are realized in the form of a flange  1011  and a union nut  1012 . 
         [0027]    The device coupling means  125  is realized in the form of a double nipple  125 . The utilization of a double nipple  125  makes it possible to connect the tube section  100  and the feedthrough  120 . 
         [0028]    An externally realized thread  1251  of the double nipple  125  can be screwed into one side of the feedthrough  120  of the coupling device  12  whereas the union nut  1012  can be screwed on an additional external thread  1251 . In this way, a pressure-tight connection between the tube sections  100  and the feedthroughs  120  is produced. 
         [0029]    The partial section through a coupling device  12  illustrated in  FIG. 2  shows threaded sections  1201  that respectively feature an internal thread and channel sections  1202  that respectively form the feedthroughs  120  extending within the coupling device  12 . An external thread  1251  of the double nipple  125  can be screwed into the threaded section  1201  such that the tube sections  100  can be coupled to the feedthroughs  120  in a pressure-tight fashion. After the modularly designed tube lines  10  have been assembled, the fracking fluid can be pumped through the tube sections  100 , the feedthrough  120  in the coupling device  12  and through additional tube sections  100 . 
         [0030]    The tube sections  100  used in this case are illustrated in a partially sectioned fashion in  FIG. 3  and realized in the form of corrugated metal tubing with annular corrugation. However, it is also possible to use corrugated metal tubing with helical corrugation. In this case, the braiding  1000  is preferably realized in the form of a double braiding  1000  that shields the corrugated outer surface of the tube sections  100 . 
         [0031]    The internal thread  10120  of the union nut  1012  is screwed on the external thread  1251  of the double nipple  125  manually and subsequently tightened with a wrench, wherein the flange  1011  is flanged on the double nipple  125  with or without an additional seal. In this case, the double nipple  125  features a thickening in the form of a hexagon such that the double nipple  125  also can be easily fastened in the threaded section  1201  of the feedthrough  120  in a removable fashion by means of a wrench. 
         [0032]    The exemplary coupling option shown, in which a double nipple  125  is used as device coupling means  125 , may also be realized differently. It would be possible, for example, use coupling sleeves or the coupling device  12  may feature rigid connecting pieces, on which the tube coupling means  101  can be positively and/or non-positively fastened in a removable fashion. These connecting pieces may be integrally formed or welded on and thereby integrally connected to the coupling device  12 . A simple and quick coupling should be achieved, wherein it is advantageous to forgo device coupling means  125 , tube coupling means  101  and additional seals of plastic because plastics are negatively affected by the temperatures occurring during hydraulic and/or pneumatic fracturing. 
         [0033]      FIG. 4 a    shows a section through a coupling device  12 , in which the device coupling means  125  and the tube sections  100  were omitted in order to provide a better overview. The cylindrically designed coupling device  12  shown features a cable feedthrough  121  in the form of a central through-bore extending in the direction of the longitudinal cylinder axis. A traction cable  11  can be placed into this cable feedthrough  121 , wherein said traction cable can be inserted through an insertion slot  123 . In this case, the insertion slot  123  is realized about radially referred to the centrally extending cable feedthrough  121  and extends through the entire body of the coupling device  12 . 
         [0034]    Cable fastening means  1211  are provided for attaching the traction cable  11 . The cable fastening means shown consist of a recess  1211 ″′, through which a threaded pin  1211 ″ can be inserted. 
         [0035]    Since significant tensile forces act upon the coupling device  12  when the traction cable  11  is inserted and attached and the tube sections  10  are in the coupled state, a slot safety  124  is provided in order to absorb forces acting upon the insertion slot  123  or the slotted coupling device  12  in the region of the insertion slot  123  and to thereby protect the coupling device  12  against distortion. Furthermore, the slot safety  124  additionally secures an attached traction cable  11  from sliding out of the coupling device  12 . 
         [0036]    In this case, the slot safety  124  features a bore  124 ″ and a safety screw  124 ′ that can be screwed through the slot safety  124 ; see  FIG. 5 . 
         [0037]    In the side view of a coupling device  12  illustrated in  FIG. 4 b   , the traction cable  11  extending in the direction of the cylinder axis is indicated with a broken line. The traction cable  11  is laterally inserted into the coupling device  12  through the insertion slot  123  until it is positioned in the central cable feedthrough  121 . This figure shows two recesses  1211 ″′, by means of which the traction cable  11  can be held in two positions in the cable feedthrough  121 . 
         [0038]      FIG. 5  shows a top view of the coupling device  12 , in which the inserted traction cable  11  is illustrated in a sectioned fashion. A clamping element  1211 ′ is linearly screwed in about perpendicular to the longitudinal axis of the coupling device  12  by means of the threaded pin  1211 ″ traversing the recess  1211 ′″ such that the inserted traction cable  11  is clamped in position. The clamping direction is indicated with a double arrow in  FIG. 5 . 
         [0039]    The fracturing tube system  1  described herein can be assembled by lowering a first coupling device  12  with first tube sections  100  coupled thereto and the traction cable  11  fastened thereon into a bore hole. The ends of the first tube sections  100  on the introduction side are coupled to a second coupling device  12  and the traction cable  11  is inserted through the insertion slot  123  of the second coupling device  12  and removably attached to the cable feedthrough  121 . Subsequently, second tube sections  100  can be attached to the second coupling device  12  such that the second coupling device  12 , as well as the second tube sections  100 , can be lowered into the bore hole with the aid of the traction cable  11 . If the base of the bore hole is not yet reached, the fracturing tube system  1  can be extended to the desired overall length by connecting additional coupling devices  12  and tube sections  100  to one another and to a traction cable  11 . 
         [0040]    The fracturing tube system  1  preferably features a continuous one-piece traction cable  11 . However, it would also be conceivable to divide the traction cable  11  into cable sections such that it can be extended to a desired overall length of the fracturing tube system  1 . However, this would reduce the stability of the traction cable  11  and could potentially lead to undesirable twisting, which cannot be readily prevented. 
         [0041]    In this case, the traction cable  11  used consists of a steel cable or high-grade steel cable with a diameter of at least ten millimeters. Such a traction cable  11  is capable of absorbing the tensile forces of four tube sections  100  with a respective length of about one hundred meters. 
         [0042]    In order to additionally protect the individual tube sections  100  against abrasion, a protective helix of steel or high-right steel may furthermore be wound over the circumference of the tube sections  100 . This spirally wound protective helix can be fastened in the coupling part of the tube sections  100 . In addition to the use of a protective helix, a person skilled in the art is familiar with other suitable protection options. 
         [0043]    The tube sections  100  may furthermore consist of multilayer plastic tubes that are resistant to hydrocarbons. Plastic tubes of this type are familiar to a person skilled in the art and can be used with or without braiding. 
         [0044]    Instead of the functional connection between the tube sections  100  and the coupling device  12  described herein, it would also be possible to produce the connection by means of hydraulic rapid-action coupling. Since the tensile force acting upon the tube sections  100  is absorbed by the traction cable  11  in this case, it is also possible to use hydraulic rapid-action couplings that cannot be subjected to tensile loads. 
       LIST OF REFERENCE SYMBOLS 
       [0045]      1  Fracturing tube system 
         [0046]      10  Tube line (composed of four or more sections)
         100  Tube section
           I Section length     1000  Braiding/braid   
             101  Tube coupling means
             1011  Flange     1012  Union nut
                 10120  Internal thread   
               
               
 
         [0054]      11  Traction cable/steel cable (one) 
         [0055]      12  Coupling device
             120  Feedthrough (four or more)
                 1201  Threaded section (internal thread)     1202  Channel section (cylindrical)   
                 121  Cable feedthrough (central through-bore)
                 1211  Cable fastening means
                     1211 ′ Clamping element     1211 ″ Threaded pin     1211 ″′ Recess   
                   
                 123  Insertion slot     124  Slot safety
                 124 ′ Safety screw     124 ″ Bore   
                 125  Device coupling means/double nipple     1251  External thread