RU2197594C2 - Heat-insulated pipe string - Google Patents

Abstract

FIELD: oil and gas producing industry, particularly, oil production with use of heat carrier injection into oil formation for prevention of permafrost thaw and deposition of paraffin in tubings in oil recovery from wells in regions with permafrost grounds and also in other branches of national economy for heat insulation of pipelines. SUBSTANCE: essence of the invention consists in that heat-insulated pipe string including concentric sections of external pipes with joint unit and sections of internal pipes contains, between sections in annular space, heat-insulating and screening materials, expansion joints, elastic rings installed between adjacent sections of pipes in their joint unit. Expansion joints are made in the form of loop-shaped clamp with cylindrical shells, and they are located on joints of string sections at level of joint units. Expansion joints are located at one end of internal pipe and rigidly connected by one cylindrical end of shell to external surface of internal pipe, and by the other cylindrical end of shell, they are installed with sliding on internal pipe and rigidly connected with internal surface of external pipe. EFFECT: higher operating reliability of heat-insulated pipe strings. 2 cl, 2 dwg

Description

 The invention relates to the oil and gas industry, in particular to production using injection of coolant into the oil reservoir, to prevent thawing of permafrost and to prevent paraffin deposits in tubing when producing oil from wells in areas with permafrost soils, and can also be used in others sectors of the economy for thermal insulation of pipelines.

 A known column of thermally insulated pipes, which includes sections of external pipes with threads at the ends and internal pipes, which are fixed to each other and sealed at one end with a welded diaphragm, and a sleeve with a sealing ring is installed on the other. A coupling with cylindrical sealing inserts is installed between the sections of the internal pipes, the coupling being made of the same material as the pipes, and the sealing inserts and rings are made of a material with a higher coefficient of linear thermal expansion than the external and internal pipes. Behind the diaphragm there is a layer of heat insulator and a centralizer. The outer pipe sections are connected by a threaded sleeve [1].

 The disadvantage of this column of thermally insulated pipes is the unreliability of sealing the coupling, especially at high temperatures and pressures and alternating temperatures, due to the impossibility of perfect roundness and cylindricality (in pairs) of the sliding surfaces of the inner pipe of the outer diameter and the inner diameter of the cylindrical insert, microgaps are possible. In addition, the design complexity of this coupling joint as a whole.

 The closest technical solution is a thermally insulated column (taken as a prototype), which includes concentrically arranged sections of the external pipes with the connection unit and sections of the internal pipes, in the annular space between which are insulating and shielding materials, expansion joints made in the form of corrugated diaphragms connecting at the ends of the sections of the external and internal pipes, elastic rings installed between the diaphragms of the adjacent pipe sections in the node of their connection [2].

 The disadvantages of this insulating column are unreliability in conditions of high temperatures and associated elongations of the inner pipes due to the destruction of corrugated diaphragms.

 The objective of the invention is to increase the reliability of a thermally insulated column by reducing stresses in it. The problem is solved in that in a thermally insulated column, which includes concentrically arranged sections of external pipes with a connection unit and sections of internal pipes, in an annular space between which are insulated and shielding materials, expansion joints, elastic rings installed between adjacent pipe sections in the assembly their connections, while the expansion joints are made in the form of a loop-shaped bracket with cylindrical shells and they are placed at the joints of the section columns at the level of the connecting nodes, and expansion joints for thermal expansion are located at one end of the inner pipe and are rigidly connected by one cylindrical end of the shell to the outer surface of the inner pipe, and the other cylindrical end of the shell is mounted slide-movably on the inner pipe and rigidly connected to the centering ring mounted slide-movably on the inner pipe and rigidly connected to the inner surface of the outer pipe. The problem is also solved by the fact that the radii of the bends of the compensator for thermal expansion are equal to one third of the annular space gap, and the distance between the inner walls of the base of the loop-shaped bracket is h = 2 / 3R, where h is the distance between the inner walls of the base of the loop-shaped bracket, mm; R is the bending radius of the bracket, mm

Salient features of the claimed invention in comparison with the prototype are:
- expansion joints temperature expansion made in the form of a loop-shaped staples with cylindrical shells, and they are placed at the joints of the column section at the level of the connecting node;
- expansion expansion joints are located at one end of the inner pipe and are rigidly connected by one cylindrical end of the shell to the outer surface of the inner pipe, and the other cylindrical end of the shell is mounted sliding-movable on the inner pipe and rigidly connected to a centering ring mounted sliding-movable on the inner pipe and rigidly connected to the inner surface of the outer pipe;
- the radii of the bends of the compensator for thermal expansion are equal to one third of the annular space gap, and the distance between the inner walls of the base of the loop-shaped bracket is h = 2 / 3R, where h is the distance between the inner walls of the base of the loop-shaped bracket, mm; R is the bending radius of the bracket, mm

 The expansion of the expansion of thermal expansion in the form of a loop-shaped bracket with the same inner and outer radii equal to one third of the gap of the annular space, and the distance between the inner walls of the loop-shaped bracket of the base, equal to h = 2 / 3R, significantly equalizes the internal stress on its internal and external walls during injection steam into the formation, i.e. during compression and decompression of a loop-shaped bracket - a compensator for thermal expansion, the possibility of its extension is also significantly increased, which simplifies the generally insulated column and improves the reliability of its operation. The above essential distinguishing features were unknown from the patent and scientific and technical information, therefore, the invention meets the criterion of "novelty", that is, the essential distinguishing features are "new."

 Given that the essential distinguishing features are not obvious to a person skilled in this field of knowledge, we believe that the invention meets the criterion of "inventive step".

 With regard to "industrial applicability", the invention meets this criterion, since it has been completed with working drawings, all the necessary documentation and preparations are being made for the production of a prototype, and a test bench has been made.

 The invention is illustrated by drawings, where in Fig.1 shows a thermally insulated column in section, in Fig.2 - node I in Fig.1.

 The thermally insulated column of Fig. 1 consists of concentrically (coaxially) located sections of the outer pipes 1 with nodes of the joints 2, sections of the inner pipes 3, in the annular space between which are placed insulating and shielding materials 4, centering the lower 5 (according to the scheme), centering the upper 6 ( according to the scheme) of rings installed between the external 1 and internal 3 pipes, a compensator of thermal expansion 7, made in the form of a loop-shaped bracket, ring bands 8 and elastic (sealing) rings 9. The lower 5 (according to the scheme) are centering e rings are rigidly welded to one of the ends of the sections of the outer 1 and inner 3 pipes. Clutches 2 (connection nodes) hermetically connect the outer pipes 1. The elastic (sealing) rings 9 are tightly sandwiched between the centering upper 6 and lower 5 rings.

 Expansion expansion joints 7, made in the form of a loop-shaped bracket with cylindrical shells, are placed at the junction of the column section at the level of the connecting unit (sleeve) 2 and are located at one end of the inner pipe 3, and are rigidly connected by one cylindrical end of the shell to the outer surface of the inner pipe 3 and the shells are mounted slider-movably on the inner pipe with another cylindrical end face and are rigidly connected to the centering upper 6 (according to the diagram) mounted slide-movably on the inner pipe 3 and tightly connected to the inner surface of the outer pipe 1. The bending radii of the expansion joint 7 are equal to one third of the annular gap, and the distance between the inner walls of the base of the loop-like bracket is h = 2 / 3R, where h is the distance between the inner walls of the base of the loop-shaped bracket, mm; R is the bending radius of the bracket, mm

 To improve the working conditions of the bending surfaces of the expansion joint 7 on both sides of the curly corrugations on its cylindrical shells round (in section) buffer rings-bandages 8 are rigidly installed.

Figure 2 (node I) shows the operation of the expansion joint 7 in two positions:
- the first position, when the steam supply to the formation through a thermally insulated column is suspended, and the temperature in the column is compared with the temperature of the natural environment, while the internal pipes return to their original position, and the expansion expansion compensator is expanded, i.e. assumes the same installation "open"position;
- the second position is shown in figure 2, when under the influence of steam (when injecting steam into the reservoir), the internal pipes are lengthened, and the compensator is shortened - the position is "squeezed" (shown in dashed in figure 2).

 The stroke S of the temperature expansion compensator is set by calculation, depending on the temperature of the injected steam into the formation and the length of the section of the thermally insulated column.

 The manufacture and operation of a thermally insulated column of figure 1 is as follows.

 Having previously installed and secured the bandages 8 on both sides of the corrugations on the cylindrical shells of the expansion joint of the temperature expansion 7, weld it to the inner bore of the centering ring 6. Thus, a blank “compensator - centering ring” is obtained. First, put the centering ring 5 on the stepped end of the inner pipe 3 and weld it with a tight seal. Then, on the other end of the inner pipe 3, a blank “compensator - centering ring” is put on with the cylindrical part of the shell inside and at a certain distance from the end, it is welded to the inner pipe 3. Then, they are wound on the inner pipe 3 in the section between the centering ring 5 and the thermal expansion compensator 7 alternating layers of heat-insulating material 4 foil (shielding) and basalt canvas. The last layer is fixed with wire ties. Then, on the inner pipe 3 with centering rings, a temperature expansion compensator 7 with bandages and heat insulating material 4, put on the outer pipe 1 and centering rings are welded to it. To improve the operating conditions of the expansion compensator 7, it is proposed to connect it in an expanded state (preload) for half a step (S / 2) with the inner surface of the outer pipe 1.

 Thus, the obtained thermally insulated sections of pipes are assembled into a string and lowered into the well like ordinary tubing, pre-installing between the centering rings seals 9 (elastic material - the ring) and screwed with couplings 2 on the outer pipes 1.

 With constant or periodic injection of the coolant into the oil reservoir through a thermally insulated column, the linear dimensions of the internal pipes 3 of FIG. 1, 2 increase or decrease freely, because the inner pipe 3 is rigidly connected at one end to the outer pipe 1 through the centering ring 5, and the other slidingly movable, since this end of the inner pipe 3 is hermetically connected to the outer pipe 1 through the expansion joint 7 and the centering ring 6. In this case, the inner pipes the columns are telescopically interconnected, and expansion joints made in the form of a loop-shaped bracket 7 compensate for changes in the axial linear dimensions of the inner tubes 3. This will dramatically reduce the internal pressure tension in the pipe section of the column, and thereby increase the reliability of the thermally insulated columns. The advantage of the claimed invention in comparison with the prototype is to reduce material costs for well equipment by increasing the durability of the service of thermally insulated columns and the ability to work at higher temperatures and pressures of the coolant, as well as with a large depth of wells.

Sources of information
1. USSR copyright certificate 1609940, 6 IPC E 21 B 17/00; F 16 L 59/00. Publ. 11/30/90.

 2. USSR author's certificate 857425, 6 IPC E 21 B 17/00; E 21 B 43/00; F 16 L 59/00.

Claims (2)

 1. A thermally insulated column, including concentrically located sections of the external pipes with the connection unit and sections of the internal pipes, in the annular space between which are insulating and shielding materials, expansion joints, elastic rings installed between adjacent pipe sections in the connection unit, characterized in that the expansion joints are made in the form of a loop-shaped bracket with cylindrical shells, and they are placed at the joints of the column section at the level of the connection node-negative, and the thermal expansion compensator are arranged at one end of the inner tube and is rigidly connected at one end cylindrical shell with an outer surface of the inner tube and the other end face of the cylindrical shell slidably mounted on a sliding inner tube and rigidly connected to the inner surface of the outer tube.  2. The thermally insulated column according to claim 1, characterized in that the bending radii of the expansion joint compensator are equal to one third of the annular space gap, and the distance between the inner walls of the base of the loop-shaped bracket is h = 2 / 3R, where h is the distance between the inner walls of the base of the loop-shaped bracket mm; R is the bending radius of the bracket, mm

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