Patent Publication Number: US-2012024603-A1

Title: Apparatus for  a pipe string of a geological drill hole, pipe string, method for operating a geological drilling gear and method for producing a pipe string for a geological drill hole

Description:
The invention is in the field of technologies for geological boreholes. The invention relates in particular to an apparatus for a pipe string of a geological drill hole, a pipe string of a geological drill hole, a method for operating a geological drilling machine and a method for producing a pipe string for a geological drill hole. 
     BACKGROUND OF THE INVENTION 
     Geological bores are needed and constructed in connection with various applications. These include for example production of oil or natural gas. The production of geological bores to great depths is however also necessary in connection with geothermal energy. Geothermal energy involves using the energy stored in the earth, insofar as it can be obtained. 
     Appropriate systems in the form of drilling and production devices have been proposed for the different applications for geological bores, namely in particular the construction of a geological drill hole and the subsequent production of a fluid through the drill hole. 
     After a drill hole has been constructed in connection with an oil reservoir, it is usually sufficient during the subsequent production of oil when starting to exploit the reservoir to use the natural energy in the oil reservoir so that the oil transports itself upwards. If the reservoir pressure drops, what is known as a gas lift method can be used, during which a gas or a liquid is introduced into the produced column by means of a compressor pump system in order to support the transport of the oil upwards. 
     Various production apparatuses designed for the gas lift method are known. For example, U.S. Pat. No. 3,937,280 describes what is known as a lift apparatus for producing oil. A gas is introduced through an inner cavity of a hollow rod system, which gas passes outwards through openings in the pipe surrounding the inner cavity to enter the liquid to be conveyed, that is, in particular oil, and to support the transport thereof upwards. In a pneumatic system for producing oil using the gas lift method in U.S. Pat. No. 6,298,918 B1, a gas is transported downwards along an outer surface of a production pipe to enter the oil to be conveyed through a central cavity in the production pipe and to support the transport of the oil upwards. 
     The use of the gas lift method in connection with the production of a fluid from a geothermal source is known from U.S. Pat. No. 4,787,450. A separate pipeline is used to introduce an inert gas into the geothermal fluid to be produced and to support the production thereof. The separate pipeline for the gas to be supplied is in one embodiment cemented in an intermediate space between an inner production pipe and an outer pipe. 
     The above-mentioned production of the geothermal fluid requires that a suitable geological drill hole has been constructed beforehand. When such a drill hole is constructed, geological drilling machines are used, on which a drilling tool is mounted at the lower end of the drill string or rod system. A flushing liquid is guided to the drilling head through a cavity in the drill string, which liquid is transported back upwards on the outside of the drill string after exiting in the region of the drilling head. In the process drilling chips produced with the drilling head are transported away by means of the flushing liquid. During operation of the drilling machine, a substantial portion of the flushing liquid including drilling chips can be lost in geological formations by the flushing liquid penetrating strata and collecting there. In this manner the strata, which are for example malm limestones, become blocked. It is then provided for such blockages to be cleared again by introducing an acid. An economic loss also results due to the loss of the flushing liquid. 
     U.S. Pat. No. 6,607,042 B2 describes a method for constructing a geological drill hole in which in one embodiment a gas is injected into flushing liquid transported upwards to affect a circulation pressure of the flushing liquid in the region of the drilling head. It has been found that the circulation pressure at the bottom of the drill hole can be reduced by means of the gas injection. The gas is supplied through an intermediate space between an outer pipe and an inner pipe, in which the flushing liquid is transported upwards. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to specify improved technologies for constructing or forming a geological drill hole. More efficient handling of drilling flushing liquid should in particular be made possible, and damage to drilled geological formations should be minimised or completely avoided. 
     The object is achieved according to the invention by an apparatus for a pipe string of a geological drill hole according to independent Claim  1 , a pipe string of a geological drill hole according to independent Claim  14 , a method for operating a geological drilling gear according to independent Claim  15  and a method for producing a pipe string for a geological drill hole according to independent Claim  16 . Advantageous configurations of the invention form the subject matter of dependent subclaims. 
     According to one aspect of the invention, an apparatus for a pipe string of a geological drill hole is created, with a pipe string element and a fluid supply line which is arranged outside the pipe string element, extends along the pipe string element and is connected to a fluid injection device on the pipe string element, by means of which a fluid supplied through the fluid supply line can be introduced into an inner space of the pipe string element. 
     According to a further aspect of the invention, a pipe string of a geological drill hole, in particular of a geothermal energy drill hole, is created with the above-mentioned apparatus, the apparatus being at least partially cemented in. 
     A further aspect of the invention provides a method for operating a geological drilling machine with the above-mentioned apparatus, the method comprising the following steps: supplying an operating liquid to an operative drill head mounted on a drill rod system, conducting the operating liquid back away from the drill head through an inner space of a pipe string element, supplying a fluid via a fluid supply line extending along and outside the pipe string element and adding the supplied fluid from the fluid supply line via a fluid injection device formed on the pipe string element to the operating liquid conducted away in the inner space of the pipe string element. 
     Another aspect of the invention relates to a method for installing a pipe string for a geological drill hole with the above-mentioned apparatus, in which a pipe string element is cemented, and during the cementing a pumping pressure is reduced by a fluid being supplied via a fluid supply line extending along and outside the pipe string element and added to a space to be cemented via a fluid injection device provided on the pipe string element. The reduction of the pumping pressure lowers the risk of geological formations breaking up. 
     With the aid of the invention new technologies for constructing a geological drill hole with a pipe string are created, which allow more efficient handling of the drilling machine used in comparison with the prior art. The introduction of the fluid supplied via the fluid supply line in the inner space of the pipe string element allows the density conditions in the operating liquid conveyed upwards, which is usually what is known as a flushing or drilling flushing liquid to be influenced in a targeted manner. For example, the density of the operating liquid can be reduced by introducing a gas. The pressure conditions in the drill hole are thereby adjusted during hole. Also in connection with the method for installing a pipe string, the supply and introduction of the fluid make it possible to regulate the pressure, namely to reduce the pumping pressure during cementing, 
     The provision of the fluid supply line outside the pipe string element makes possible an independent design and configuration of the inner space of the pipe string element on the one hand and of the fluid supply line on the other. The pipe string element can be optimised for the intended purpose, in particular the return of the operating liquid and the injection of the fluid into the operating liquid transported back. Independently of this, the fluid supply line can be correspondingly optimised to its purpose, namely the supply of the fluid to be injected into the operating liquid. 
     In a possible embodiment, a plurality of fluid injection devices can be formed along the pipe string element. These can be distributed for example over the entire circumference of the pipe string element. If a plurality of fluid injection devices are formed on the pipe string element, they can be fed either via one fluid supply line or via separate fluid supply lines or separate fluid supply line sections. The supplied fluid can be a gas or a liquid. The fluid supply line is preferably formed in a gastight manner in one configuration. 
     A preferred development of the invention provides for the fluid supply line to be configured as a pipeline formed separately from the pipe string element, the walls of which pipeline are free from wall sections formed together with the walls of the pipe string element. 
     In an expedient configuration of the invention, it can be provided for the fluid supply line to be arranged at least in sections on the outside of the pipe string element. The fluid supply line can lie completely or partially on the outside of the pipe string element. A combination of sections of the fluid supply line which lie on the outside of the pipe string element and fluid supply line sections kept at a distance therefrom can be provided. In one configuration, retaining tabs can be used to fix the fluid supply line to the pipe string element. Independently of this configuration, it can be provided in one configuration for the fluid supply line to be routed outwardly on a drill hole head in a fluid-tight manner. 
     One advantageous embodiment of the invention provides for the fluid supply line to be configured as a high pressure line. 
     A development of the invention preferably provides for the fluid supply line to be connected with at least one section through a connecting element which is arranged on the pipe string element and by means of which the pipe string element is connectable to a further pipe string element. In one embodiment, the connecting element is configured as a connecting bushing with which the pipe string element and the further pipe string element are connected to each other. 
     In an advantageous configuration of the invention, it can be provided for the fluid injection device to be provided in the connecting element. The fluid injection device is connected to an opening in the walls of the pipe string element through which the fluid is injected into the inner space of the pipe string element. 
     One development of the invention can provide for an inspection opening to be provided on the connecting element. Access to for example the fluid supply line and/or the injection device is made possible via the inspection opening. The inspection opening is preferably provided with a removable cover. 
     A preferred development of the invention provides for the injection device to be formed with a counterforce element which is configured to allow the injection of the supplied fluid into the inner space of the pipe string element only when a counterforce provided by the counterforce element is overcome. In one exemplary embodiment, the injection device is formed with a non-return valve, it being possible for valves operating according to the electronic or the mechanical non-return principle to be used. In this configuration, the one or the plurality of injection devices also prevent fluid from escaping from the interior of the associated pipe string element. If a plurality of fluid injection devices are arranged at different depths over the length of the pipe string, it can be provided in the configuration for the counterforce to be overcome to increase downwards. In this manner the fluid is injected via the different fluid injection devices at increasing pressure one by one. 
     In an expedient configuration of the invention, it can be provided for the counterforce provided by the counterforce element to be adjustable. 
     One advantageous embodiment of the invention provides for the pipe string element to be connected to a further pipe string element via an associated connecting element, the fluid supply line also extending along the further pipe string element and being connected to a further fluid injection device on the further pipe string element, by means of which the fluid supplied through the fluid supply line can be introduced into an inner space of the further pipe string element. 
     A development of the invention preferably provides for the injection device and the further injection device to be attached to separate supply line sections of the fluid supply line which are configured to feed the injection device and the further injection device individually. Alternatively, the injection device and the further injection device can be arranged in series. 
     In an advantageous configuration of the invention it can be provided for the further injection device to be formed with a further counterforce element which is configured to allow the injection of the supplied fluid into the inner space of the further pipe string element only when a counterforce provided by the further counterforce element is overcome. In one configuration, the further fluid injection device is formed with a non-return valve, which is identical to or different from the non-return valve of the fluid injection device. 
     One development of the invention can provide for the counterforce provided by the further counterforce element to be different from the counterforce provided by the counterforce element. 
     The method for operating a geological drilling machine can be developed according to one of the above-mentioned configurations of the apparatus for the pipe string or according to a combination of a plurality of the said configurations. 
    
    
     
       DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS OF THE INVENTION 
       The invention is explained in more detail below using preferred exemplary embodiments with reference to figures of a drawing. Here: 
         FIG. 1  shows a schematic diagram of a pipe string design with a plurality of pipe strings of a geological drill hole, 
         FIG. 2  shows a schematic diagram of an arrangement with three pipe string elements which are connected with connecting bushings, and 
         FIG. 3  shows a schematic diagram of an arrangement with three pipe strings of a geological drill hole, which are cemented in. 
     
    
    
       FIG. 1  shows a schematic diagram of a pipe string design of a geological drill hole. There is a plurality of pipe strings  1 , . . . ,  5 , which are each cemented in, shown with different diameters. The pipe strings  1 , . . . ,  5  are terminated at the top with the aid of associated flanges  6 , . . . ,  10 . Three pipe strings  2 ,  3 ,  4  are provided on the outside with a respective fluid supply line  11 ,  12 ,  13  via which a fluid, in particular a gas, can be fed into the respective inner space of the pipe strings  2 ,  3 ,  4 , which is shown schematically in  FIG. 1  by means of arrows. The fluid supply lines  11 ,  12 ,  13  are routed outwards at the top through the associated flanges in a pressure-tight manner. Dashed lines in  FIG. 1  indicate possible branches of the fluid supply lines  11 ,  12 ,  13  to intermediate valves (not shown) along the pipe string design. 
     The fluid supply lines  11 ,  12 ,  13  can be configured as high pressure lines, for example consisting of reinforced plastic, reinforced rubber or metal. During production, an endless pipeline from a drum or screwed, flanged or welded individual pipes can be used. 
     The fluid supply lines  11 ,  12 ,  13  are attached on the outside in the region of a drill hole head (not shown), preferably by means of a high pressure quick coupling, a stop nut or a flange design. 
       FIG. 2  shows a schematic diagram of an arrangement with pipe string elements  20 ,  21 ,  22  of a pipe string which are connected to each other with the aid of connecting bushings  23 ,  24  in cross section. On the outside of the pipe string elements  20 ,  21 ,  22 , two fluid supply lines  25 ,  26  which are configured as high pressure lines are arranged along them, via which lines a fluid, for example air or an inert gas, can be supplied to non-return valves  27 ,  30  which are arranged in the connecting bushings  23 ,  24  and act as fluid injection devices. The supplied fluid can be introduced via the non-return valves  27 ,  30  in an inner space  31 , through which flushing or drilling flushing liquid flows upwards during operation. Arrows indicate a flow path of the fluid in  FIG. 2 . 
     According to  FIG. 2 , a respective inspection opening  32  is formed on the connecting bushings  23 ,  24 , which opening is closed with a cover. 
       FIG. 3  shows a schematic diagram of an arrangement with three pipe strings  40 ,  41 ,  42  of a geological drill hole, which are cemented in. 
       FIG. 3  shows a schematic diagram of a section of a pipe string design with three pipe strings  40 ,  41 ,  42  of a geological drill hole at the time of sinking the drill hole from the pipe string  42  with a drill head which corresponds to the inner diameter of the pipe string  42 . A plurality of fluid supply lines  43 ,  44 ,  45  act to supply a fluid, for example air or an inert gas. The supply of the fluid makes it possible to reduce the pumping pressure in the process of cementing the pipe strings when introducing the cement. The supplied fluid is introduced via fluid injection devices  46 ,  47 ,  48 . The plurality of fluid supply lines  43 ,  44 ,  45  are partially deactivated again after successful drilling and cementing of already covered, higher drill hole sections. The fluid supply lines  44 ,  45  are still active for continued drilling and cementation of a pipe string still to be introduced inside the pipe string  42 . 
     A plurality of fluid injection devices, distributed over a pipe string and operated via one or a plurality of fluid supply lines, make it possible with optimum adding of light fluids or gases to maintain the flushing circuit in a drill hole in the short term, even with the flushing head unscrewed from the drill rod system and pumps stopped. This time can generally be sufficient to reset a drill string without in the meantime having to fill a rod system interior with flush medium manually in order to maintain the often desired continuous flushing circuit in a drill hole during such stoppage times. Pressure peaks on geological formations, which can arise especially in deep drilling sections when restarting the flushing pumps after such a resetting process, can thereby largely be avoided. 
     The features of the invention disclosed in the above description, the claims, and the drawing can be of significance individually as well as in any combination for the implementation of the invention in its different embodiments.