MXPA96005778A - Isolated double-wall pipe and method of installation of the mi - Google Patents

Abstract

The present invention relates to a column (46) of the double wall insulated pipe, adapted to be suspended from a head (58) of the well, having a column (21) of internal pipe, formed of several internal pipes and a column (22) of radially external pipe, formed of several external pipes, the columns of pipes are independent of each other, in addition to axially fixed the columns of pipes one in relation to the other at the upper end of the column of the pipe, although the axial fixation can also be provided at the lower end of the pipe columns if desired. An annular insulating space (30) between the columns (21, 22) of pipes is hermetically sealed at both opposite ends and can be evacuated. The columns of internal and external pipes can be put into operation in a well that uses conventional oil well drilling technology and there is no mechanical connection between the columns (21, 22) of internal and external pipes, especially in the connections of the respective internal and external tube lengths. To keep the inside of the column (22) of the external pipe free from the formation liquids before the column (21) of the internal pipeline is put into operation in the well and sealed against the column of the external pipe at its lower end, a temporary plug (31) initially closes the lower end of the column of the external pipe and deactivates that the liquid can influence through the column (46) of the thermally insulated double pipe.

Description

ISOLATED DOUBLE-WALL PIPE AND METHOD OF INSTALLATION OF THE (SAME DESCRIPTION OF THE INVENTION This invention relates to insulated, double-walled tubing and to a method for installing such tubing in a well, such as a geothermal or oil well, and there is a requirement to provide excellent insulating properties. thermal in a tubular pipe column, where it is required to bring warm or hot liquids to the surface from the bottom of a [0 depth] In other words, it is required to maintain the cooling of the liquid in its path from the bottom of the well to the upper part of the well to a minimum, although the temperature of the surrounding formations can fall by an average of 3 ° C per 100 meters, such applications are as follows: 1. Geothermal wells which produce hot water from 15 aquifers (total formation or partially saturated with water) at rather low flow rates where the thermal water would otherwise cool to a considerable amount in the route to the surface, to lose by this the thermal energy available to the consumers on the surface. 2. Closed loop geothermal wells where the heat exchanger thermal fluid, which is commonly water, is pumped to the bottom of a well in an annular space formed between a column of the cemented pipe and a column of the pipe in so much that it extracts thermal energy from the surrounding formations and subsequently transports the thermal energy to the surface through the column of the pipe. 3. Oil wells that produce crude oil with a high content of bitumen or paraffin. Without efficient thermal insulation, oil in The column of the pipeline cools down considerably as the oil flows to the installation of the surface. Once the temperature drops to a level which is specific to the type of oil, the bitumen or paraffin begins to change to the solid state and adheres to the inner wall of the pipe column. As a result, the resistance to flow is increased due to the decreased cross-section of the tubes, such that the pumping rods stick and break. To pump the cold and therefore highly viscous oil through the sections of the pipeline near the well head, a high unnecessary amount of energy is required. 4. To produce oil that is already highly viscous in the i? formation that takes oil at the bottom of the drilling where the hot steam is compressed to the formation around the borehole to heat the viscous oil and thus, improve its flow behavior. It is required that the losses of heat on the way to the surface are low so as not to cause any unnecessary pressure drop of the flow in the column of the production pipes. 0 Pipe strings or columns that are covered with glass wool or stone and then wrapped with sheets or strips of thin steel sheets to protect the insulating layer against water are frequently used for surface applications. However, water can enter the insulating material through small holes or fissures that may occur in the surrounding cover and reduce the insulating properties of such string or string or pipe column. Therefore. This known method can not be used to thermally isolate production line chains exposed to high pressure liquids in the annular space between the pipe column and a deep well casing pipe. Pipe made of glass fiber has a lower thermal conductivity than steel and is normally used for pipes or pipe chains for corrosive media rather than for the purpose of thermal insulation, because the thermal properties are usually insufficient. The limits of the temperature and the lower resistances also reduce the possible range of applications of the pipe made of such material. Fiberglass material is also considerably more expensive than steel pipe of the same diameter and can not be used in oil wells equipped with reciprocating pumping rods. As well, inventory costs would rise if glass fiber tubing has to be maintained in stock in addition to standard steel tubing that is generally used in oilfield operations. Up to now, the cns or chains of thermally insulated injection and production pipes have sometimes been used to carry out the injection of steam into the wells to obtain an increased thermal efficiency of the system. The chains or cns of pipe, which often have a length of more than 1,000 meters, are constructed from individual lengths of double-walled pipe, each of which usually has a length of about 9 meters - which is equivalent to range of 2 API pipe joints - to be put into operation and recovered by oil facilities in the same way as cns or single wall pipe chains. The most common version of such a pipe cn or chain is shown in the "Cataloque Composite of Oil Field Equipment," Ve 1, page 988H, 35a. revision, 1982 - 83, published by Gulf Publishing in the United States of America. The pipe cn of the prior art will now be described with reference to Figures 1 and 2 of the accompanying drawings, in which Figure 1 shows a longitudinal cross section of a pipe cn and Figure 2 shows a sectional view longitudinal, enlarged, detailed cross section of a part of the pipe cn shown in figure 1 to show more clearly the union between the lengths of the pipe. The thermally insulated pipe shown in Figure 1 illustrates an individual length of thermally insulated pipe having connections at opposite ends thereof, but it will be appreciated that in practice there would be a plurality of such pipe lengths used to form a pipe cn. thermally isolated Figure 2 shows the construction details of the threaded connections used to form an isolated pipe length connected together. In Figures 1 and 2, an inner tube 1 has the inner diameter thereof increased at the opposite ends and the inner tube 1 is positioned concentrically to the inside of an end tube and the opposite ends of the inner tube are welded to the outer tube 2. In the annular space 3 formed between the outer wall of the inner tube and the inner wall of the outer tube is an insulating means such as air. The outer tube 2 is slightly longer than the insulated double wall section, such that the threads of the connecting screws can be cut at opposite ends of the outer tube. The double box couplings 4 are used to link a length of double insulated pipe to the next double pipe in an axial direction. In order to avoid internal diameter changes in each joint connection in the chain or cn of the pipe, which would undesirably increase the dynamic pressure losses in the fluid flow, for example oil, the non-insulated section sleeves 5 Insert at the ends of the tube at the time of putting into operation the chain or cn of pipe in the well. Mechanically, such chains or pipe cns satisfy all the strength requirements for deep wells. However, even in the ideal case where the probing liquid does not enter the annular space 6 between the sleeve 5 and the box coupling 4, a considerable amount of thermal energy is lost through the electrically conductive bridges created by the tubes internal and external that are welded together and also for having a mechanical connection between the sleeve 5 and the box coupling 4. However, water or oil will usually enter the annular space 6 to further reduce the efficiency of the insulation. Any mechanical damage to the inner tube 1 caused by the reciprocating or corrosion-causing pumping rods will allow the liquid to flow into the annular space 7 between the inner and outer tubes, to cause by this a thermal bridge that will not be immediately visible on the surface since the annular area is closed at the end of each inner tube because the inner tube is welded to the outer tube. Another disadvantage of this type of chain or pipe column with insulation is the requirement to weld the internal and external pipes together. In the drilling industry, it is usual to avoid, whenever possible, welding tools or equipment that are positioned at the bottom of the well because such welds are the starting points for corrosive leaks. Thus, in the example of the column of thermally insulated pipe present, the welding between the inner and outer pipes can also be the starting point for a corrosive leak. If corrosion starts from inside the annular space 3 between the two tubes, it will not be detected visually or by the non-destructive inspection methods commonly used in the oil and gas industry. When the steel pipes leave the production line of a factory they usually have wide tolerances of the length of width. To correspond with the internal and external pipes of double-walled pipe, the pipes have to be cut to correspond in length, in order to increase the cost of the material. The main reason why the chains or columns of double-walled pipe are not more frequently used is the high purchase cost, which is a multiple of the cost of normal pipes, as well as the increased delivery times for welded joints manufactured especially and finally, but not minimum, the inventory levels increased. Another double wall pipe for thermal insulation purposes is described in reference EP-A-0138603. This reference overcomes the difficulty of the prior art mentioned above by providing a passage or passage between the connection of the two connected lengths of pipe, such that the annular space in the respective pipe lengths are connected together. Thus, in EP-A-0138603 the ends of the inner and outer tubes are connected together by a wall and a small passage or passage having a cross-sectional area smaller than the cross-sectional area of the annular space that is axially extends axially from the annular space outward from the contion of the internal and external tubes. Because the location of the passage or passage in each tube may not exactly align with each other, such that the axially longitudinally outermost portion of the passage is enlarged in the cross-sectional area to ensure that when the two lengths Double-walled pipes join together, their respective steps or passages will be interconnected. On an internal and external side of the passage or passage where the two lengths of pipe are joined together, respective annular seals are provided to create a pressure seal between the annular space within the column of the insulated pipe and the inner liquid and around the isolated chain.

The annular space can be filled with any desirable insulated gas or liquid and can alternatively be evacuated from the surface. Thus, the interconnected annular space can be used to inspect leaks in any of the seals or in the walls of the pipe. If the annular space is initially filled with gas, a leak is indicated by an increase in pressure which will rise until the pressure in the annular space is balanced by the pressure of the liquid, either inside the column of the pipe isolated or outside of it. Again, this reference has the disadvantage that the double wall pipe with insulation, described above and if either the internal or external pipe had a leak, the leaking substance will spread throughout the annular space of the entire column of The pipe. In such a case, it is difficult to locate the position of the leak which may be in the elastomeric seals inside or outside the passage. Another known double wall pipe for reverse circulation drilling is described in patent GB-1204026. In this reference, two concentric tubes are connected to each other by fins that are welded in the annular space between the inner and outer tubes. The inner tube is recessed or recessed at each end of the outer tube and the outer tube is provided with a screw thread to join individual tube lengths together. When a column of the pipeline is put into operation to the well, a pontoon sleeve having seals on opposite ends thereof is inserted over the inner tube of the column section of the upper and lower pipe, to seal the inner tubes of the two different double wall sections together. Thus, the sleeve extends to the next joint of the pipe, where it is sealed against the inner tube of the next section. The requirement that the sleeves that connect the internal tubes to each other is added to the cost of purchase, storage and maintenance of the pipe column. However, a double-walled pipe constructed in accordance with this reference also has the disadvantages mentioned above in which the inner and outer tubes are mechanically joined together, to thereby create a thermal connection between the inner and outer tubes. A thermally insulated pipe for transporting liquids and gas over the surface of the earth is described in WO 91/19129. This reference describes two concentric steel tubes separated by an annular space and in the annular space there is an insulating material formed of microfibers or microscopic mineral fibers having sufficient compression force to keep the inner tube properly separated from the outer tube. The insulating material in the annular space is required to carry the weight of the column of the internal pipe, since the chains or columns of the annular pipes are approximately horizontal, without the insulating material losing its insulating properties. To have the appropriate insulating properties, reference is made to solid insulators, which are extremely porous. These support insulators are added to the cost of the chain or column of the pipe but, even worse, liquids which can pass into space through a leak in one of the chains or columns of the internal or external pipes will enter the pores of the insulating material of the insulators, in such a way that the material has to be replaced.

There is no description in this reference of the putting into operation of such pipe column of generally independent concentric tubular elements designed for more or less horizontal pipes to a probe or well, generally vertical, filled with liquid and where the annular space between The internal and external tubes would have to be sealed against the influx of liquids contained in the well. The equipment for the oil fields is not designed to operate simultaneously or pull concentric pipe columns with different diameters. The oil field piping joints, according to the worldwide accepted API standard, they do not have uniform lengths and the lengths of the joints fluctuate considerably. Only with the non-standard, more expensive tubes, machined to identical lengths, can the columns or concentric pipe chains be put into operation simultaneously in a slow operation. Although pipes above the surface are usually welded because at any time the surface can be accessed at any point along the line, in distinction, the pipes at the bottom of the well are usually threaded. that, otherwise, the tube column has to be cut into sections each time the well has to be pulled for any reason. It is an object of this invention to substantially mitigate the difficulties of the prior art mentioned above. According to a first aspect of this invention, there is provided a double-walled insulated pipe column, adapted to be suspended from supporting means, the pipe column comprises internal and external pipes with a thermally insulating space between the internal and external pipes. , characterized in that the column of the pipe comprises several lengths of external tubes mechanically joined together to form a column of the external pipe and several lengths of internal pipes mechanically joined together to form a column of the internal pipe, the columns or Internal and external pipe chains are discrete and are separated from one another over substantially all their lengths. In general, the internal and external pipe columns are separated from each other without any mechanical connection between them, except at one or both ends thereof. In a presently preferred embodiment, separable seaming means are provided at the lower end of the outer pipe column to prevent the ingress of liquid into the column of the inner pipe. Advantageously, the insulating space is filled with a gas or liquid medium or the space is evacuated substantially. Advantageously, the columns of internal and external pipes are mechanically joined together at the upper end of the pipe column or at both ends of the pipe column, ie the upper and lower ends of the column of the isolated pipe only.

Advantageously, the external and internal tubes are adapted to withstand a pressure that exceeds a hydrostatic pressure of the fluid in or within the column of the insulated pipe. In a preferred embodiment, the internal pipe column is prestressed and the outer pipe column is pre-compressed so as not to exceed the predetermined allowable stress levels in the internal and external pipe columns respectively, caused by variations in internal and external temperature. Advantageously, the column of the internal pipe and / or the external pipe column are provided with means that compensate for the temperature of the axial length. In another preferred embodiment, an insulation means is provided in the insulation space to maintain concentricity between the internal and external pipe columns to prevent the column of the inner pipe from coming into contact with the column of the external pipe. According to a second aspect of this invention, a method is provided for installing a double wall insulation pipe column, which includes the steps of: providing a first length of the outer pipe with sealing means at a lower end, in use The same, to prevent the entrance of the liquid to the external tube, mechanically join a second length of the external tube to the end of the first external length, far from the sealing means to form a column of the external pipe, suspend the column of the external pipe of the support means, locating the first and second joined lengths of the inner tube that form a column of the internal pipe to the interior of the column of the external pipe, the first and second internal lengths of the pipe are mechanically joined together and the column of the internal pipe is separated from the column of the external pipe to provide a space of thermal insulation between the chains of internal and external tubes, the internal and external tubing columns are discrete and are separated from one another over substantially the entire length thereof. Preferably, more than two lengths of the outer tube and the outer tube are connected, respectively, together. In a preferred embodiment, the sealing means is separated by increasing the fluid pressure within the lengths of the inner tube or by mechanical means. Advantageously, in order to equalize the hydrostatic pressure against the outside of the sealing means in a sounding, the column of the inner pipe is filled with a liquid and the sealing means are subsequently deactivated, for example pumped into the open air. Advantageously, the internal and external tubes are mechanically joined together at the upper end of the column or at the extreme limits of the pipe column, that is, at the upper and lower ends of the isolated column only.

Advantageously, the connection between the respective external ends and between the respective internal tubes is a leak-proof connection, preferably provided by a threaded screw connection or by welding. Advantageously, at the lower end of the pipe column, a lower substructure is joined on the column of the external pipe and an acute pipe is joined on the column of the internal pipe to form a seal with the column of the external pipe. Advantageously, a seal is provided for the space in the upper part of the pipe column to provide a vacuum in the space. In a preferred embodiment, wherein the column of the double-walled insulation pipe is located in a column of the production pipe, the cross-sectional area between the column of the double wall insulation pipe and the column of the Production pipeline is larger than the cross-sectional area of the inside of the inner pipe. Advantageously, means are included that compensate for the temperature of the axial length, either in the column of the internal and / or external pipe. An advantage of this invention is that the temperature in the space at the lower end of the pipe column is approximately equal to the temperature at the lower end of the column of the inner pipe when in use. The present invention provides an insulated pipe column that has minimal heat loss and which uses normal oilfield piping joints with positive seal connections without introducing a third insulating layer, generally tubular solid material in the space between the inner and outer tubes, as required in the world patent WO 91/19129. If a liquid enters the insulating space between the internal and external tubes, it is easy to verify when a leak appears to locate and replace the leaking element. Welding on the pipe column is not necessary, although it can be provided if desired. Once removed from the well, the pipe joints are easy to clean and inspect, so that they can be reused in the same well or for any other purpose that requires a pipe column composed of steel grade pipe joints. Used with positively sealing connections. The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a longitudinal axial cross section of the insulated double wall pipe known in the art. Figure 2 shows a detail of a gasket used in the known art of Figure 1, Figure 3 shows an axial cross section of a first embodiment of a column of the double wall insulated pipe according to this invention, Figure 4 shows a longitudinal axial cross-section of a second embodiment of a column of the insulated double-walled pipe according to this invention, Fig. 5 (a) shows a partial longitudinal cross section of a pipe column according to this invention, with the eccentric inner tube with respect to the outer tube, Figure 5 ib) shows a cross section along the double arrow head lines BB of Figure 5 (a), Figure 6 (a) shows a view in longitudinal cross section of a portion of a column of the double wall insulated pipe according to this invention, centered by the centering elements of low thermal conductivity, Figure 6 (a) shows a cross-section along the double-headed arrow lines BB of Figure 6 (a), Figure 7 (a) shows a portion of a double-walled insulated pipe column of According to this invention, in which the column of the inner pipe is provided with thermal expansion elements, Figure 7 (b) shows a cross section along the lines of double arrow head BB of Figure 7 (a ), Figure 8 shows a column of the double wall insulated pipe according to this invention, located in a geothermal well with closed circuit heat production, Figure 9 shows a column of the double wall insulated pipe according to the invention. This invention, in a petroleum or thermal well producing water, Figure 10 shows a well head to support the internal and external pipe columns and to seal both columns together and also shows the provision for joining a vacuum pump. I to improve the thermal insulation, and Figure 11 shows a lower seal between the columns of the internal and external pipe. In the figures similar reference numerals denote similar parts. Figure 3 shows a longitudinal cross-section of a column of the double-walled insulated pipe, in which a column of the inner pipe 21, formed of various lengths of the inner pipe (pipe), joined together in the axial direction, is provided. and a column of the outer pipe 22 formed of several individual lengths of outer pipe (pipe), which are axially joined together, the column of the inner pipe 21, preferably, is located concentrically to the interior of the column of the pipe. external pipe 22. The individual pipes of the internal pipe column are connected together by the threaded connections 23 and the individual pipes of the outer pipe column are connected together by threaded connections 24 and both of these threaded connections 23, 24 are, normally , selected type connections which are leak proof of gas and liquid. At the upper end of the column of the double-walled insulated pipe, the columns of internal and external pipes are secured against relative axial movement with respect to each other by means of an element 25 which fixes the upper end of the two columns of tubes together. Also, at the upper end of the columns of the pipe there is a peripheral seal 26 which seals the columns of the internal and external pipe together at the upper end limit of the columns of the pipe. The element 25 which prevents axial movement and the seal 26 can be combined in a single construction element. At the lower end of the columns of the pipe, the columns of internal and external pipes are also sealed together by a peripheral seal 27 to seal and hermetically seal a space 30 between the columns of the internal and external pipe. The space 30, which is typically an annular space, since the columns of the pipe are usually circular in cross section, can be filled with any desired gas or insulating liquid, via a valve 29 at the upper end of the column of the external pipe 22. Alternatively, the annular space can be substantially evacuated. A temporary sealant plug 31 is located at the lower end of the outer pipe chain to close the lower end of the outer pipe column 22 and is sealed to the lower outer tube by a peripheral seal 28. The use of the temporary sealant plug 31 will be described later in this. A further embodiment of the invention, shown in Figure 4, which is similar to the embodiment of Figure 3, except that, to avoid excessive relative movement in the lower seals 27, 28 caused by frequent temperature fluctuations or caused Due to the friction between the column of the internal pipe and the pumping rods, the columns of the independent internal and external pipes are also fixed axially to each other by the fixing element 32 positioned between the seals 27 and 28. Thus, in general, In this invention the columns of the inner and outer pipe 21, 22 are discrete and are separated from each other without any mechanical connection between them over substantially all lengths thereof, except at one or both ends thereof. Because the wells in which the columns of the pipe are located are rarely quite vertical or straight. in such a way that the longitudinal axis of the column of the internal pipe 21 may not be concentric with the longitudinal axis of the outer column 22. Depending on the total inclination, as well as the changes in azimuth and inclination, both columns may be placed in contact, as shown in figures 5 (a) and 5 (b). The eccentricity is, however, limited by the minimum spacing caused by the largest external diameter of the threaded coupling connection 23 of the column of the inner pipe 21 against the body of the inner pipe. This effect can lead to a line contact between the columns of the internal and external pipe in some of the couplings, to cause some minor heat losses. Such heat losses, however, are not significantly lower than those associated with the prior art. Figures 6 (a) and 6 (b) show how these lower heat losses can be avoided by using a centering device 34 made of a material having low thermal conductivity. Such centering devices are located at a minimum of predetermined points along the longitudinal axis and are attached to the outside of the column of the internal pipe to avoid any metallic contact and to minimize contact between the columns of the internal and external tubular pipe. , with the exception of the extreme limits of the thermally insulated double pipe column. If both columns of the pipe are actually fixed to each other at their opposite ends, as shown in Figure 4, temperature fluctuations can lead to undesirably high axial stresses in one or other of the columns of the pipe. Figures 7 (a) and 7 (b) show an embodiment of the invention in which a compensator 35 of the axial length is located in a tube of the column of the internal pipe 21, although it will be understood that the compensator can also be Use in a tube of the column of external pipe 22. or both columns of the pipe. Referring now to Figure 8, a column of the double walled insulated pipe 46 is installed inside a column of the production pipe 47 of a cemented borehole. Commonly, the borehole is provided with a first column of pipe 48, a second column of pipe 49 radially internally and still another third column of pipe 50 radially internal. Both columns of the internal and external pipe of the thermally insulated double pipe column are supported by the hamper of the axial movement 25 formed in the head 58 of the well and thus, the columns of the internal and external pipe 21, 22 are set against the relative axial movement. In close proximity to the obstacle of the axial movement 25 is the seal 26 that closes the annular space between both columns of the pipe. At the lower end of the column of the thermally insulated pipe 36 are the seals 27, 28 (not shown in FIG. 8) and the fastener 32 (not shown separately in FIG. 8) which can be provided. In this embodiment of the invention, a vacuum pump can be connected to the closed annular space via the valve 29 between the two columns of the pipe, to create a vacuum that acts as the insulation medium inside the pipe column. thermally insulated double wall 46. When geothermal energy is extracted from the formations surrounding the well, a cold fluid medium, such as a liquid, preferably water, is pumped via valve 51 into the space between the column of the production pipeline 47 and the column of the double-walled insulated pipe 46. The temperature of the rock formations increases with depth, so that the circulating medium becomes hotter as it approaches the lower end of the pipe column. 46. Then the circulating fluid flows back to the surface through the tubes of the column of the inner pipe 21 and is withdrawn via the valve 52. Preferably the sectional area The cross section of the column of the internal pipe of the column of the double-walled insulated pipe 46 is much smaller than the flow area between the column of the insulated double-walled pipe and the column of the pipe of production 47, such that the period during which the circulating liquid could lose thermal energy as it flows back to the surface is less than the time available to heat the medium when it moves down through the column of the production pipeline. Figure 9 shows another embodiment of the present invention that uses the column of insulated double-walled pipe for a well producing oil. In distinction from the modality of Figure 8, no circulating fluid is cold. it is pumped into the space between the column of the insulated pipe 46 and the column of the production pipe 47, in such a way that the temperature difference between the liquid flowing upwards through the column of the insulated pipe 46 and the environment surrounding is less severe. The flow velocity of oil-producing wells is, however, often extremely small, so that the total temperature losses are still considerable if the column of the pipe is not insulated. Oil, especially with a high bitumen or paraffin content, is extremely sensitive to temperature. Once the temperature of the oil or the inner wall of a pipe column decreases to a temperature lower than a specific minimum for the particular type of oil, the bitumen or paraffin partially solidifies to block the flow path inside the pipe column or inevitably cause the breaking of the pump rods. The purpose of the thermally insulated double pipe column of this invention is, therefore, to maintain the oil temperature completely at the well surface above the critical temperature for solidification. In the embodiment of figure 9 column 47 of the production pipeline is shown in its passage through a formation containing oil or aquifer 60.

Figure 10 shows an enlarged view of the head of the well used in the embodiments of Figures 8 and 9. One embodiment of a lower sealing means for the annular space between the columns of the internal and external pipe and to cover the column of the outer pipe is shown in Figure 11. A sharp polished organ 70 is threadably attached to the lower end of the column of the inner pipe 21 to seal against the seal elements 28 (a) and 27 (b) of the seal 27 , which is referenced in Figures 3 and 4. A lower substructure 71 is attached to the lower end of the outer pipe column 22 and the seals 27 (a), 27 (b) to form an airtight gas seal and to the liquid between the lower substructure 71 and the acute organ 70. The lower substructure 71 is formed in two parts 71 (a), with which the seals 27 (a), 27 (b) cooperate and a lower part 71 (b) with which the seals 28 (a), 28 (b) of seal 28, shown in FIGS. 3 and 4, cooperate. The plug 32 is located in the lower part 71 (b) of the lower substructure. The plug 21 is inserted and sealed against the bottom substructure part 71 (b) to prevent the entry of liquid into the column of the double pipe 46 while the column of the double pipe is in operation in the well. As mentioned above, it is desirable for a particular application, that both columns of the inner and outer pipe be axially fixed to each other near the seal 28. A device known in the petroleum industry as a "pressurized fastener" is a to effect such axial fixation. Now we will describe the method to install a column of double wall insulated pipe.

Beginning with the bottom substructure 71 which preferably has permanent seals 27 (a), 27 (b), 28 (a), 28 (b) and the temporary plug 31 installed, the column of the external pipe 22 is put into operation in the hole. The temporary plug 31 prevents liquids contained in the well from entering the interior of the pipe column. The lower substructure is joined by a leak-proof connection to a first outer tube of the outer pipe column and as many tubes are connected as necessary until the substructure of the bottom reaches its final position, after which the column of the external pipe is suspended in landslides in the well head 58 (shown in Figures 8 and 9). Starting with the acute organ 20, the column of the internal pipe is now in operation to the column of the empty outer pipe until the acute organ 20 reaches the lower substructure 71 and seals against it by virtue of the seals 27 (a ), 27 (b). To equalize the hydrostatic pressure against the bottom of the temporary plug caused by the liquid in the borehole, the column of the inner pipe 21 is filled with liquid and the temporary plug is deactivated after this, for example when being pumped in the open air. Before or after filling the inner pipe column with liquid and deactivating the temporary plug 31, the column of the inner pipe is suspended from the well head and sealed against the column of the outer pipe at the top of the pipe. water well. To inspect whether the space (annular space) between the columns of the pipe is hermetically sealed, the space may not be evacuated instantaneously, but closed while a manometer controls the development of pressure in the space between the columns of the pipe. internal and external pipe. If the pressure continues to rise after a small initial increase caused by the increase in the initial air temperature between the columns of the pipe, this is an indication of one or more leaking connections, one or more holes in the pipes and / or a seal for leaks in the bottom of the pipe column. In such a case, the insulation has to be rectified immediately. As soon as the system is sealed, a vacuum pump is attached to the valve 29 between both columns of the pipe and the space is evacuated. Following this procedure, the well can be used to produce water or oil or to produce thermal energy as a closed-circuit geothermal system. In some circumstances, it may be desirable to prestress the column of the double wall insulated pipe by pulling the column of the inner pipe against the column of the outer pipe, to thereby stretch the column of the inner pipe and compress the column of the outer pipe. Such pretensioning may be required in various thermal conditions. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following

Claims (19)

1. Claims 1. A pipe column, insulated, double walled, adapted to be suspended from support means, the column of the pipe comprises internal and external tubes with a thermally insulating space between the internal and external pipes, characterized in that the Pipe column comprises several lengths of extemal tubes mechanically joined together to form a column of the external pipe and several lengths of internal pipes mechanically joined together to form a column of the internal pipe, the columns of the internal and external pipe they are discrete and are separated from one another over substantially all the lengths thereof.
2. 2. A double wall pipe column according to claim 1, characterized in that a removable sealing means is provided at the lower end of the outer pipe column to prevent liquid from entering the column of the internal pipe.
3. 3. A column of double-walled pipe according to claim 1 or 2, characterized in that the insulating space is filled with a gas or liquid medium or the space is substantially evacuated.
4. 4. A double-walled pipe column according to any of the preceding claims, characterized in that the columns of the internal and external pipe are mechanically joined together at the upper end of the pipe column or at both ends of the pipe column. the pipe, this is only the upper and lower ends of the column of the insulated pipe.
5. 5. A double wall pipe column according to any of the preceding claims, characterized in that the internal and external pipes are adapted to withstand a pressure that exceeds the hydrostatic pressure of the fluid in or outside the column of the insulated pipe.
6. 6. A double-walled pipe column according to any of the preceding claims, characterized in that the column of the internal pipe is prestressed and the column of the outer pipe is pre-compressed so as not to exceed the predetermined permissible stress levels in the columns of the pipe. internal and external caused by internal and external temperature variations.
7. 7. A column of double-walled pipe according to claim 6, characterized in that the column of the internal pipe and / or the column of the outer pipe are provided with means that compensate for the temperature of the axial length.
8. 8. A double wall pipe column according to any of the preceding claims, characterized in that an insulating separation means is provided in the insulation space to maintain the concentricity between the columns of the internal and external pipe to prevent the column of the Internal pipe is put in contact with the outer pipe column.
9. 9. A method for installing a double wall insulated pipe column, characterized in that it includes the steps of: providing a first length of the outer tube with sealing means at a lower end, in use, thereof to prevent liquid from entering the pipe external, mechanically joining a second length of the outer tube to the end of the first external length, far from the sealing means, to form a column of the external pipe, suspend the column of the outer pipe from the support means, locate the first and second joined lengths of the inner tube forming a column of the inner pipe to the interior of the outer pipe column, the column of the internal pipe of the supporting means will be suspended, the first and second lengths of the inner pipe are mechanically joined joint way and the inner pipe column is spaced from the outer pipe column to provide a thermal insulation space in Between the columns of the internal and external pipe, the columns of the internal and external pipe are discrete and are separated from each other over substantially all the lengths thereof.
10. 10. A method of comfort with claim 9, characterized in that more than two lengths of the outer tube and the inner tube are joined, respectively, together.
11. 11. A method according to claim 9 or 10, characterized in that the sealing means are removed by increasing the fluid pressure within the lengths of the inner tube or by mechanical means.
12. 12. A method according to claim 11, characterized in that in order to equalize the hydrostatic pressure against the outside of the sealing means in a sounding, the column of the inner pipe is filled with a liquid and the sealing means are subsequently deactivated.
13. 13. A method according to any of claims 9 to 12, characterized in that the inner and outer tubes are mechanically joined together at the upper end of the pipe column or at the ends of the pipe column.
14. 14. A method according to any of claims 9 to 13, characterized in that the connection between the respective external tubes and between the respective internal tubes is a leak-proof connection.
15. 15. A method according to any of claims 9 to 14, characterized in that at the lower end of the pipe column, a lower substructure is joined on the column of the outer pipe and a sharp organ is attached on the pipe column internal to form a seal with the column of the external pipe.
16. 16. A method according to any of claims 9 to 15, characterized in that a seal is provided for the space in the upper part of the pipe column to provide a vacuum in the space.
17. 17. A method according to any of claims 9 to 16, characterized in that the column of the double-walled insulating pipe is located in a column of the production line, the cross-sectional area between the column of the double wall insulated pipe. and the column of the production pipeline is larger than the cross-sectional area of the pipe interior.
18. 18. A method according to any of claims 9 to 17, characterized in that the temperature in the space at the lower end of the pipe column is approximately equal to the temperature at the lower end of the column of the internal pipe when it is at use.
19. 19. A method according to any of claims 9 to 18, characterized in that the means that compensate the temperature of the axial length are included in the internal and / or external pipe columns.