The invention relates to the construction of pipelines. The method is intended to eliminate temperature stresses in pipelines of the “pipe-in-pipe” type in the operating sealed state of the internal pipeline (in the absence of excess pressure in the interpipe space) without installing special compensators inside. The method consists of placing sealing units in the annulus space, made in the form of spiral sleeves tightly wound to each other. The hoses are made of elastic, air-impermeable material; they are wound with a small gap along the ends of the “pipe-in-pipe” type pipeline onto the internal pipeline in the form of two spirals, each with a length no less than the internal diameter of the pipeline. The spirals are inserted into the annulus, the hoses are filled with air, the ends of the annulus are closed with annular plugs rigidly connected to the outer pipeline, ensuring free movement of the outer and internal pipelines relative to each other in the absence of excess pressure in the annulus. The technical result of the invention is to increase the reliability of protection environment. 2 salary f-ly.

The invention relates to the construction of pipelines, mainly underwater crossings, and is intended to eliminate temperature stresses in pipelines of the “pipe-in-pipe” type in operating condition without installing special compensators inside and to prevent liquid hydrocarbons pumped through the internal pipeline from entering the environment in the event of a leak in the internal pipeline .

It is known to construct pipelines of the “pipe-in-pipe” type, in which the interpipe space is sealed by filling spiral hoses loosely wound towards each other along the entire length of the internal pipeline with hardening cement mortar. Temperature stresses in the internal pipeline are suppressed by installing special compensators in the form of closed metal cavities spirally wound towards each other (A.S. USSR No. 1460512, class F16L 1/04, 1989).

The disadvantage of sealing the interpipe space in this case is the mandatory installation of temperature stress compensators inside the “pipe-in-pipe” type pipeline, which significantly complicates and increases the cost of the entire known “pipe-in-pipe” type pipeline design.

Closest in essence technical solution is the sealing of pipeline cavities, in which the seals are made in the form of tightly wound spiral hoses, the hoses are filled with incompressible fillers (RF patent, No. 2025634, Class F16L 55/12, 1994).

In this case, complete sealing of the space is not ensured with a sufficiently large excess pressure in front of the seal. Such pressure can be in front of the sleeve seal if it is installed in the annulus. If the internal pipeline of the “pipe-in-pipe” system is damaged (tightness is broken), the polluting liquid can leak through the spiral gaps between tightly wound hoses with round cross-section, non-deformable under pressure, with incompressible filler and enter the environment. Such sealing of the pipeline cavity has a limited scope and can only be used when the pressure in front of the hose seal is close to atmospheric, i.e. only when carrying out repair work to eliminate (cut out) damaged sections of conventional (not “pipe-in-pipe”) pipelines.

The purpose of the invention is reliable protection environment from spills of liquid hydrocarbons in case of violation of the tightness of the internal pipeline of the “pipe-in-pipe” system and ensuring compensation of temperature stresses in the internal pipeline in working condition (without violating its tightness) due to the free axial movement of the internal pipeline relative to the external one in good condition of the “pipe-in” system pipe."

Reliable environmental protection is achieved due to the fact that the sealing of the annulus space is carried out by installing tightly wound spiral-shaped hoses made of elastic air-tight material into the annulus space, which are filled with a compressible filler (air). If the tightness of the internal pipeline is broken, the excess pressure in the annulus increases, compresses and tightly presses the spirally wound hoses with air to the walls of the outer and internal pipelines, thus ensuring complete tightness of the annulus.

Providing compensation for temperature stresses of the internal pipeline in operating condition (in the absence of excess pressure in the interpipe space) is achieved due to the fact that air is supplied to the spirally wound hoses at low pressure, close to atmospheric pressure, at which there are practically no friction forces between the hoses and the walls of the internal pipeline , preventing the relative longitudinal movement of the external and internal pipelines in good condition.

The method is implemented as follows. The hoses are made of an elastic air-tight material, they are wound with a small gap along the ends of the pipe-in-pipe pipeline onto the internal pipeline in the form of two spirals, each with a length of at least the internal diameter of the pipeline, the spirals are inserted into the interpipe space, the hoses are filled with air, the ends of the interpipe space closed with ring plugs rigidly connected to the outer pipeline, ensuring free movement of the outer and inner pipelines relative to each other in the absence of excess pressure in the interpipe space. To eliminate temperature stresses in a “pipe-in-pipe” pipeline, impermeable hoses wound in the form of a tight spiral on the internal pipeline are filled with air at a pressure that ensures free movement of the pipelines relative to each other in the absence of excess pressure in the interpipe space.

To prevent spontaneous unwinding of the spirals when inserting them into the annulus, the ends of the spirals are connected with a flexible connection or their ends are limited by ring bushings.

FORMULA OF THE INVENTION

1. A method for sealing the annular space of pipelines of the “pipe-in-pipe” type, including placement in pipelines of sealing units made in the form of spiral hoses with fillers tightly wound to each other, characterized in that the hoses are made of an elastic air-tight material, they are wound with a small gap at the ends of the “pipe-in-pipe” type pipeline onto the internal pipeline in the form of two spirals, each with a length no less than the internal diameter of the pipeline, insert the spirals into the annular space, fill the sleeves with air, the ends of the annular space are closed with ring plugs rigidly connected to the outer pipeline, ensuring free movement of external and internal pipelines relative to each other in the absence of excess pressure in the interpipe space.

2. The method according to claim 1, characterized in that to eliminate temperature stresses in a “pipe-in-pipe” pipeline, impermeable hoses wound in the form of tight spirals on the internal pipeline are filled with air at a pressure that ensures free movement of the pipelines relative to each other in the absence excess pressure in the annulus.

3. The method according to claim 1, characterized in that to prevent spontaneous unwinding of the spirals when inserting them into the annulus, the ends of the spirals are connected with a flexible connection or their ends are limited by annular bushings.

After drilling a well in loose sandy soils, a stage begins aimed at strengthening the casing pipes. At the same time, you should protect the barrel from damage and aggressive influences groundwater, corrosion and other negative phenomena. We are talking about a process such as cementing wells.

Carrying out cementing work on your own is quite difficult, but it is possible if you have knowledge about the technologies for carrying out the event. We will tell you why you need to carry out cementing and what you need to pay attention to when performing work. For clarity, the material contains thematic photos and videos.

Well cementing is a process that follows immediately after completion. The cementing procedure consists of introducing cement mortar, which hardens over time to form a monolithic wellbore.

The cement mortar in this case is called “plugging”, and the process itself is called “plugging”. A complex engineering process called well cementing technology requires certain knowledge and special equipment.

In most cases, water sources can be plugged with your own hands, which is much cheaper than hiring specialists.

Well cementing is a set of measures aimed at strengthening the annulus and casing from destructive lateral pressure of rocks and the effects of groundwater

Correctly performed plugging of water wells contributes to:

• ensuring the strength of the well structure;
• protecting the well from ground and surface waters;
• strengthening casing pipe and protecting it from corrosion;
• increasing the service life of the water source;
• elimination of large pores, voids, gaps through which unwanted particles can enter the aquifer;
• displacement of drilling mud by cement, if the former was used during drilling.

The quality of the produced water and performance characteristics wells. Cementing is also carried out for abandoned wells that will no longer be in operation.

Image gallery

Method for repairing a culvert under an embankment

Author: Vylegzhanin Andrey Anatolyevich

The invention relates to the field of repair and, in particular, to methods for repairing culverts. The purpose of the invention is to reduce the labor intensity of filling the space between the defective pipe and the new pipe with concrete solution. The method of repairing a culvert under an embankment involves temporarily diverting a watercourse and installing a new pipe into the internal outline of the defective pipe with a gap. The pipe is equipped with control tubes protruding through the ceiling of the pipe into the interpipe space at a certain pitch. Filling of the interpipe space with concrete solution and its control is carried out through control tubes with their sequential plugging. The interpipe space is filled with concrete using a flexible hose placed in guides installed with outside on top of the new pipe in the interpipe space, moving it outward and removing it as the interpipe space is filled with concrete. Each section of the new pipe is formed from several rings, for example three, made of metal sheet material, preferably corrugated. 2 salary f-ly, 6 ill.

The traditional trench method of laying and replacing culverts under earthen embankments is known (Building of bridges and pipes. Edited by V.S. Kirillov. M.: Transport, 1975, p. 527, fig. XU. 14, XU 15 The disadvantage of this method is that to lay the culvert it is necessary to dig an open trench.

There is a known method for reconstructing a beam bridge by replacing it with one or two culverts (Maintenance and reconstruction of bridges. Edited by V.O. Osipov. M.: Transport, 1986, p. 311, 312, fig. X 14, X 15, X 16). This method repeats the disadvantages of the previous analogue, since it involves dismantling the upper structure of the track.

The “Method for replacing a culvert” is known, given in the description of patent RU 2183230. The method involves laying in winter time tunnel next to the defective pipe, holding it until the walls freeze, erecting support, making a vertical hole in the roadway for pouring concrete, laying a new pipe in the tunnel, pouring concrete into the space between the pipe and the tunnel through vertical hole. After completion of the work, the old tube is plugged. However, the method provides for the possibility of its implementation only in winter.

Known patent RU 2265692 “Method for repairing a culvert under an embankment.” The method includes temporary diversion of a watercourse, erection of a temporary support with an upper plate inside the defective pipe at the site of its defect and its fixation, and installation of parts of a new pipe into the defective pipe from its two opposite sides until the ends of the opposing parts of the new pipe stop against each other. To do this, releases are made in both parts for a temporary support stand, then the ends of the opposing parts of the new pipe are combined with each other and with the temporary support, the cavities between the defective and new pipes are filled with concrete mortar, and the temporary support is removed. However, the method does not disclose how the space between the defective and new pipes is filled with concrete.

The closest in technical essence to the claimed method is the “Method for repairing a culvert under an embankment”, given in the description of patent RU 2341612.

The method involves temporarily diverting a watercourse, installing sections of a new pipe into the internal outline of the defective pipe with a gap, and filling the interpipe space with concrete solution.

In the ceiling of the sections, control tubes protruding into the annulus are mounted at a certain pitch, the annulus is initially filled with concrete through the windows located in the upper part of the side walls of the section to the lower level of the windows and the windows are plugged, the ceiling part of the annulus is filled with concrete through the first tube until concrete comes out in the second tube, plug the first tube and feed concrete through the second tube until it comes out in the next tube and carry out sequential similar operations in all sections.

The disadvantage of this method is the relatively high labor intensity, since it is necessary to first make side windows to first fill the interpipe space with concrete through them, and then plug them and then sequentially fill them with concrete through the ceiling tubes.

The purpose of the invention is to reduce the labor intensity of filling the space between the defective and new pipes with concrete solution.

This goal is achieved due to the fact that in the method of repairing a culvert under an embankment, including temporarily diverting a watercourse, installing a new pipe into the internal outline of a defective pipe with a gap, equipped with control tubes protruding through the ceiling of the pipe into the interpipe space with a certain pitch, filling with concrete solution of the annulus space and its control through control tubes with their sequential plugging, according to the invention, filling the annulus space with concrete is carried out using a flexible hose placed in the annulus space with its movement outward and removal as the annulus space is filled with concrete.

The new pipe is formed from several sections made of metal sheet material, preferably corrugated.

On the outside, at the top of the new pipe, vertical guides are installed in the form of shields for placing and moving a flexible hose in them in the interpipe space, and the vertical guides are made with a certain pitch.

The interpipe space is filled with concrete solution from one end of the pipe using one flexible hose towards the other end of the pipe or two flexible hoses counter from both ends of the pipe

The gap between the defective and new pipes for filling the interpipe space with concrete is set to at least 100 mm.

The spacing between adjacent tubes to control the filling of the interpipe space with concrete is set depending on the dimensions of the culvert being repaired, and there must be at least one tube in each section or through one.

The height of the protrusion of the tubes in the interpipe space is set to create a gap between the end of the tube and the ceiling of the defective pipe of no more than 40 mm, while a plug is installed on each control tube on the inside of the ceiling after the concrete solution comes out of it.

The essence of the invention is illustrated by drawings, which show:

Figure 1 is a longitudinal section of a defective culvert before repair;

Figure 2 - cross-section of the culvert before repair (enlarged);

Figure 3 is a longitudinal section of a defective culvert at the beginning of filling the interpipe space with concrete;

Figure 4 is a longitudinal section of a defective culvert at the end of filling the interpipe space with concrete;

Fig.5 - cross-section of a culvert with an installed hose (enlarged);

Fig.6 - cross-section of the culvert after repair (enlarged).

A method for repairing a culvert 1 that has defects 2, located under an embankment 3, includes temporarily diverting a watercourse, installing sections 4 of a new pipe into the internal outline of the defective pipe 1 and filling the interpipe space 6 with concrete solution 5. To fill the interpipe space with concrete solution, sections 4 are installed with a gap H between the defective pipe 1 and sections 4 of the new pipe of at least 100 mm.

New pipe sections are made from metal sheet material, preferably corrugated.

On the outside, at the top of the sections 4 of the new pipe, vertical guides 7 are installed in the form of shields for placing and moving the flexible hose 8 in them in the interpipe space 6, and the vertical guides are made with a certain pitch.

In addition, in each section 4, either one or two, depending on the length of the pipe being restored, control tubes 9 are pre-installed, protruding into the interpipe space 6. Tubes 9 are installed to form a gap between the end of the tube and the ceiling of the defective pipe 1 more than 40 mm, while each tube 9 on the inside of the ceiling is made with the possibility of installing a plug 10 on it.

Installation of a new pipe into a defective one is carried out entirely by pre-assembling sections 4 into a pipe and dragging it into the internal outline of the defective pipe 1 or by sequentially feeding sections 4 inside the defective pipe 1 and connecting sections 4 there together into a single pipe.

Pulling the flexible hose 9 into the annulus 6 is carried out after placing and assembling sections 4 in the cavity of the defective pipe 1 or simultaneously with the supply of sections 4 into the cavity of the defective pipe 1, while the guide flaps 7 ensure the orientation of the flexible hose 8 in the annulus 6.

In addition, for large lengths of the defective pipe 1, it is possible to pull two flexible hoses 8 counter-pull on both sides of the pipe (not shown).

After placing sections 4 in the internal cavity of the defective pipe 1, the interpipe space from the open ends of pipe 1 is plugged with tampons (not shown).

Filling of the interpipe space 6 with concrete solution 5 is carried out with one flexible hose 8, moving it in the direction from one end to the other end of the pipe until it is completely removed, or with two flexible hoses 8 counter from both ends of the pipe.

The filling of the interpipe space 6 is monitored by the exit of the concrete solution 5 from the next control tube 9. After which the tube is plugged with a plug 10, and the hose 8 is pushed outward and further filling of the interpipe space 6 with the concrete solution 5 is carried out until the solution 5 comes out in the next control tube 9, plugged tube 9 with plug 10 and the cycle is repeated.

The achieved technical result is that the proposed method makes it possible to reduce the labor intensity of filling the space between the defective and new pipes with concrete solution, while simultaneously providing reliable control of the complete filling of the interpipe space.

The method was successfully tested on road repairs.

480 rub. | 150 UAH | $7.5 ", MOUSEOFF, FGCOLOR, "#FFFFCC",BGCOLOR, "#393939");" onMouseOut="return nd();"> Dissertation - 480 RUR, delivery 10 minutes, around the clock, seven days a week and holidays

240 rub. | 75 UAH | $3.75 ", MOUSEOFF, FGCOLOR, "#FFFFCC",BGCOLOR, "#393939");" onMouseOut="return nd();"> Abstract - 240 rubles, delivery 1-3 hours, from 10-19 (Moscow time), except Sunday

Bortsov Alexander Konstantinovich. Construction technology and methods for calculating the stress state of underwater pipelines “pipe in pipe”: IL RSL OD 61:85-5/1785

Introduction

1. Design of an underwater pipeline “pipe in pipe” with an interpipe space filled with cement stone 7

1.1. Double-pipe pipeline designs 7

1.2. Technical and economic assessment of the underwater transition of the pipe-to-pipe pipeline 17

1.3. Analysis of completed work and setting research objectives 22

2. Technology for cementing the interpipe space of pipelines “pipe in pipe” 25

2.1. Materials for cementing the annulus 25

2.2. Selection of cement mortar formulation 26

2.3. Cementing equipment 29

2.4. Filling the annulus 30

2.5. Cementing calculation 32

2.6. Experimental testing of cementing technology 36

2.6.1. installation and testing of a two-pipe rubbing horse 36

2.6.2. Cementing the annulus 40

2.6.3. Pipeline strength testing 45

3. Stress-strain state of three-layer pipes under internal pressure 50

3.1. Strength and deformation properties of cement stone 50

3.2. Stresses in three-layer pipes when cement stone perceives tangential tensile forces 51

4. Experimental studies of the stress-strain state of three-layer pipes 66

4.1. Methodology for conducting experimental studies 66

4.2. Model manufacturing technology 68

4.3. Test bench 71

4.4. Methodology for measuring deformations and testing 75

4.5. The influence of excess cementing pressure of the mek-pipe space on the redistribution of stresses 79

4.6. Checking the adequacy of theoretical dependencies 85

4.6.1. Methodology for planning an experiment 85

4.6.2. Statistical processing of test results! . 87

4.7. Testing of full-scale three-layer pipes 93

5. Theoretical and experimental studies of the bending stiffness of pipe-in-pipe pipelines 100

5.1. Calculation of bending stiffness of pipelines 100

5.2. Experimental studies of flexural stiffness 108

Conclusions 113

General conclusions 114

Literature 116

Applications 126

Introduction to the work

In accordance with the decisions of the 21st Congress of the CPSU, in the current five-year period, the oil and gas industries are developing at an accelerated pace, especially in the regions of Western Siberia, in the Kazakh SSR and in the north of the European part of the country.

By the end of the five-year period, oil and gas production will be 620-645 million tons and 600-640 billion cubic meters, respectively. meters.

To transport them, it is necessary to construct powerful main pipelines with a high degree of automation and operational reliability.

One of the main tasks in the five-year plan will be the further accelerated development of oil and gas fields, the construction of new ones and increasing the capacity of existing gas and oil transport systems running from the regions of Western Siberia to the main places of oil and gas consumption - in the Central and Western regions of the country. Pipelines of considerable length will cross along their path large number various water obstacles. Crossings over water barriers are the most complex and critical sections of the linear part of main pipelines, on which the reliability of their operation depends. When underwater crossings fail, enormous material damage is caused, which is defined as the sum of damage to the consumer, the transport enterprise and from environmental pollution.

Repairing and restoring underwater crossings is a complex task that requires significant effort and resources. Sometimes the cost of repairing a crossing exceeds the cost of building it.

Therefore, great attention is paid to ensuring high reliability of transitions. They must operate without failures or repairs throughout the entire design life of the pipelines.

Currently, to increase reliability, crossings of main pipelines through water barriers are constructed in a two-line design, i.e. parallel to the main thread, at a distance of up to 50 m from it, an additional one is laid - a reserve one. Such redundancy requires double the capital investment, but as operating experience shows, it does not always provide the necessary operational reliability.

Recently, new design schemes have been developed that provide increased reliability and strength of single-strand transitions.

One of such solutions is the design of an underwater pipeline transition “pipe in pipe” with an interpipe space filled with cement stone. A number of crossings have already been built in the USSR design diagram"pipe in pipe" Successful experience in the design and construction of such crossings indicates that the smoldering theoretical and constructive solutions the technology of installation and laying, quality control of welded joints, and testing of two-pipe pipelines are sufficiently developed. But, since the inter-pipe space of the constructed transitions was filled with liquid or gas, the issues related to the peculiarities of the construction of underwater transitions of “pipe-in-pipe” pipelines with an inter-pipe space filled with cement stone are essentially new and poorly understood.

Therefore, the purpose of this work is the scientific substantiation and development of technology for the construction of underwater pipelines “pipe in pipe” with an interpipe space filled with cement stone.

To achieve this goal, a large program was carried out

theoretical and experimental research. The possibility of using sub-tubes to fill the annulus space is shown.

water pipelines "pipe in pipe" materials, equipment and technological methods used in cementing wells. An experimental section of a pipeline of this type was built. Formulas are derived for calculating stresses in three-layer pipes under the action of internal pressure. Experimental studies of the stress-strain state of three-layer pipes for main pipelines were carried out. A formula has been derived for calculating the bending stiffness of three-layer pipes. The bending rigidity of a pipe-in-pipe pipeline was experimentally determined.

Based on the research carried out, “Temporary instructions for the design and construction technology of pilot-industrial underwater gas pipeline crossings for pressures of 10 MPa or more of the “pipe-in-pipe” type with cementation of the interpipe space” and “Instructions for the design and construction of offshore underwater pipelines according to the design scheme” were developed. pipe in pipe" with cementation of the interpipe space", approved by Mingazprom in 1982 and 1984.

The results of the dissertation were practically used in the design of the underwater passage of the Urengoy - Uzhgorod gas pipeline through the Pravaya Khetta river, the design and construction of sections of the Dragobych - Stryi and Kremenchug - Lubny - Kyiv oil and product pipelines, sections of the Strelka 5 - Bereg and Golitsyno - Bereg offshore pipelines.

The author thanks the head of the Moscow underground gas storage station production association"Mostransgaz" O.M. Korabelnikov, head of the strength laboratory gas pipes VNIIGAZ, Ph.D. tech. Sciences N.I. Anenkov, head of the well fastening detachment of the Moscow deep drilling expedition O.G. Drogalin for assistance in organizing and conducting experimental studies.

Technical and economic assessment of the underwater transition of the pipe-to-pipe pipeline

Pipe-in-pipe pipeline crossingsTransitions of main pipelines through water barriers are among the most critical and complex sections of the route. Failures of such transitions can cause a sharp decrease in productivity or a complete stop in pumping the transported product. Repair and rehabilitation of subsea pipelines are complex and expensive. Often the costs of repairing a crossing are comparable to the costs of building a new crossing.

Underwater crossings of main pipelines in accordance with the requirements of SNiP 11-45-75 [70] are laid in two threads at a distance of at least 50 m from one another. With such redundancy, the probability of failure-free operation of the crossing as a transport system as a whole increases. The costs of building a reserve line, as a rule, correspond to the costs of building the main line or even exceed them. Therefore, we can assume that increasing reliability through redundancy requires doubling capital investment. Meanwhile, operating experience shows that this method of increasing operational reliability does not always give positive results.

The results of studying the deformations of channel processes showed that the zones of channel deformations significantly exceed the distances between the laid passages. Therefore, erosion of the main and reserve threads occurs almost simultaneously. Consequently, increasing the reliability of underwater crossings should be carried out in the direction of carefully taking into account the hydrology of the reservoir and developing crossing designs with increased reliability, in which the failure of the underwater crossing was taken to be an event leading to a violation of the tightness of the pipeline. During the analysis, the following design solutions were considered: two-strand single-pipe design - pipeline strings are laid in parallel at a distance of 20-50 m from one another; underwater pipeline with continuous concrete covering; pipeline design “pipe in pipe” without filling the interpipe space and filled with cement stone; a passage constructed using the inclined drilling method.

From the graphs shown in Fig. 1.10, it follows that the highest expected probability of failure-free operation is at the underwater transition of a “pipe-in-pipe” pipeline with an annular space filled with cement stone, with the exception of a transition built by the inclined drilling method.

Currently, experimental studies of this method and the development of its basic technological solutions are being carried out. Due to the complexity of creating drilling rigs for directional drilling, it is difficult to expect widespread introduction of this method into pipeline construction practice in the near future. In addition, this method can be used in the construction of crossings of only a short length.

To construct transitions according to the “pipe-in-pipe” structural scheme with an interpipe space filled with cement stone, the development of new machines and mechanisms is not required. When installing and laying two-pipe pipelines, the same machines and mechanisms are used as during the construction of single-pipe pipelines, and to prepare cement mortar and fill the interpipe space, cementing equipment is used, which is used for cementing oil and gas wells. Currently in the system of Shngazprom and the Ministry of Oil and Gas Industry Several thousand cementing units and cement mixing machines are in operation.

The main technical and economic indicators of underwater crossings of pipelines of various designs are given in Table 1.1. Calculations were performed for the underwater crossing of a pilot section of a gas pipeline at a pressure of 10 MPa, excluding cost shut-off valves. The length of the transition is 370 m, the distance between parallel threads is 50 m. The pipes are made of X70 steel with a yield strength (et - 470 MPa and tensile strength Є6р = 600 MPa. The thickness of the pipe walls and the necessary additional ballasting for options I, P and Sh are calculated according to SNiP 11-45-75 [70].

In the “pipe-in-pipe” pipeline design with an interpipe space filled with cement stone, the wall thickness of the inner pipe is determined according to the method given in [e], the thickness of the outer wall is taken to be 0.75 of the thickness of the inner one. Hoop stresses in pipes are calculated using formulas 3.21 of this work, physical and mechanical characteristics cement stone and metal pipes are taken to be the same as in the calculation of table. 3.1.The most common two-strand, single-pipe transition design with ballasting with cast iron weights was taken as the comparison standard ($100). As can be seen from table. І.І, the metal consumption of the “pipe-in-pipe” pipeline design with an interpipe space filled with cement stone for steel and cast iron is more than 4 times

Cementing Equipment

The specific features of cementing the annulus of pipe-in-pipe pipelines determine the requirements for cementing equipment. The construction of crossings of main pipelines through water barriers is carried out in various areas of the country, including remote and hard-to-reach ones. The distances between construction sites reach hundreds of kilometers, often in the absence of reliable transport communications. Therefore, cementing equipment must have great mobility and be convenient for transportation over long distances in off-road conditions.

The amount of cement slurry required to fill the annulus can reach hundreds cubic meters, and the pressure when pumping the solution is several megapascals. Consequently, cementing equipment must have high productivity and power to ensure the preparation and injection of the required amount of solution into the annulus within a time not exceeding its thickening time. At the same time, the equipment must be reliable in operation and have sufficiently high efficiency.

Most complete specified conditions satisfies the set of equipment intended for cementing wells [72]. The complex includes: cementing units, cement mixing machines, cement trucks and tank trucks, a station for monitoring and controlling the cementing process, as well as auxiliary equipment and warehouses.

Mixing machines are used to prepare the solution. The main components of such a machine are a bunker, two horizontal unloading augers and one inclined loading auger and a vacuum-hydraulic mixing device. The bunker is usually installed on the chassis of an off-road vehicle. The augers are driven by the vehicle's traction engine.

The solution is pumped into the annulus by a cementing unit mounted on. chassis of a powerful truck. The unit consists of a cement pump high pressure for pumping the solution, a pump for supplying water and a motor to it, measuring tanks, a pump manifold and a collapsible metal pipeline.

The cementing process is controlled using the SKTs-2m station, which allows you to control the pressure, flow rate, volume and density of the injected solution.

For small volumes of interpipe space (up to several tens of cubic meters), mortar pumps and mortar mixers used for preparing and pumping mortars can also be used for cementing.

Cementing of the interpipe space of underwater pipe-in-pipe pipelines can be carried out both after they are laid in an underwater trench, and before laying on shore. The choice of location for cementing depends on the specific topographical conditions of construction, the length and diameter of the transition, as well as the availability of special equipment for cementing and laying the pipeline. But it is preferable to cement pipelines laid in an underwater trench.

Cementing of the annulus space of pipelines running in the floodplain (on the shore) is carried out after laying them in a trench, but before backfilling with soil. If additional ballasting is necessary, the annulus space can be filled with water before cementing. The supply of solution into the interpipe space begins from the lowest point of the pipeline section. The outlet of air or water is carried out through special pipes with valves installed on the external pipeline at its highest points.

After the interpipe space is completely filled and the solution begins to exit, the rate of its supply is reduced and the injection continues until a solution with a density equal to the density of the injected one begins to emerge from the outlet pipes. Then the valves on the outlet pipes are closed and excess pressure is created in the annular space. Previously, back pressure is created in the internal pipeline, preventing the loss of stability of its walls. When the required excess pressure is reached in the interpipe space, the valve on the inlet pipe is closed. The tightness of the interpipe space and the pressure in the internal pipeline are maintained for the time required for the cement mortar to harden.

When filling, the following methods of cementing the annular space of pipe-in-pipe pipelines can be used: direct; using special cementing pipelines; sectional. This consists of feeding a cement solution into the annular space of the pipeline, which displaces the air or water present in it. The solution is supplied and air or water is discharged through pipes with valves mounted on the external pipeline. The entire pipeline section is filled in one step.

Cementing using special cementing pipelines With this method, small-diameter pipelines are installed in the annulus, through which cement mortar is supplied into it. Cementing is carried out after laying the two-pipe pipeline in an underwater trench. The cement solution is supplied through cementing pipelines to the lowest point of the laid pipeline. This cementing method allows for the highest quality filling of the interpipe space of a pipeline laid in an underwater trench.

Sectional cementing can be used if there is a lack of cementing equipment or high hydraulic resistance when pumping solution, which does not allow cementing the entire pipeline section in one go. In this case, cementing of the annulus is carried out in separate sections. The length of the cementing sections depends on technical characteristics cementing equipment. For each section of the pipeline, install separate groups pipes for injection of cement mortar and outlet of air or water.

To fill the interpipe space of pipe-in-pipe pipelines with cement mortar, it is necessary to know the amount of materials and equipment required for cementing, as well as the time it takes to complete it. The volume of cement mortar required for filling between

Stresses in three-layer pipes when cement stone perceives tangential tensile forces

The stressed state of a three-layer pipe with an interpipe space filled with cement stone (concrete) under the action of internal pressure was considered in their works by P.P. Borodavkin [9], A.I. Alekseev [5], R.A. Abdullin when deducing formulas, the authors accepted the hypothesis that a ring made of cement stone perceives tensile tangential forces and its cracking does not occur under loading. Cement stone was considered as an isotropic material, having the same modulus of elasticity in tension and compression, and, accordingly, the stresses in a ring of cement stone were determined using Lame's formulas.

An analysis of the strength and deformation properties of cement stone showed that its tensile and compressive moduli are not equal, and the tensile strength is significantly less than the compressive strength.

Therefore, the dissertation work gives a mathematical formulation of the problem for a three-layer pipe with an interpipe space filled with different modulus material, and an analysis of the stress state in three-layer pipes of main pipelines under the action of internal pressure is carried out.

When determining stresses in a three-layer pipe from the action of internal pressure, we consider a ring of unit length cut from a three-layer pipe. The stressed state in it corresponds to the stressed state in the pipe when (En = 0. The tangential stresses between the surfaces of the cement stone and pipes are taken equal to zero, since the adhesion forces between them are insignificant. We consider the inner and outer pipes as thin-walled. A ring made of cement stone in the inter-tube space we consider it to be thick-walled, made of multi-module material.

Let the three-layer pipe be under the influence of internal pressure PQ (Fig. 3.1), then the inner pipe is subject to internal pressure P and external R-g, caused by the reaction of the outer pipe and cement stone to the movement of the inner one.

The outer pipe is subject to internal pressure Pg caused by the deformation of the cement stone. The cement stone ring is under the influence of internal R-g and external 2 Pressure.

Tangential stresses in the inner and outer pipes under the action of pressures PQ, Pj and Pg are determined: where Ri, &i, l 2, 6Z are the radii and wall thicknesses of the inner and outer pipes. Tangential and radial stresses in a ring of cement stone are determined by the formulas obtained for solving the axisymmetric problem of a hollow cylinder made of a different-module material under the influence of internal and external pressures [" 6 ]: cement stone under tension and compression. In the given formulas (3.1) and (3.2) the pressure values ​​Pj and P2 are unknown. We find them from the conditions of equality of the radial displacements of the mating surfaces of the cement stone with the surfaces of the inner and outer pipes. The dependence of the relative tangential deformations on the radial displacements (i) has the form [53] Dependence of the relative deformations from stresses for pipes Г 53 ] is determined by the formula

Test bench

The alignment of the pipes (Fig. 4.2) of the inner I and outer 2 and the sealing of the interpipe space were carried out using two centering rings 3 welded between the pipes. Into the outer pipe vva-. Two fittings 9 were ripped - one for pumping cement mortar into the annulus, the other for air outlet.

The interpipe space of models with a volume of 2G = 18.7 liters. filled with a solution prepared from cement Portland cement for “cold” wells of the Zdolbunovsky plant, with a water-cement ratio W/C = 0.40, density p = 1.93 t/m3, spreadability along the AzNII cone at = 16.5 cm, beginning of setting t = 6 hours 10 clays, end of setting t „_ = 8 hours 50 min”, the tensile strength of two-day cement stone samples for bending & pcs = 3.1 Sha. These characteristics were determined using the standard testing method for Portland cement cement for “cold” wells (_31j.

The compressive and tensile strength limits of cement stone samples at the beginning of testing (30 days after filling the interpipe space with cement mortar) b = 38.5 MPa, b c = 2.85 Sha, modulus of elasticity in compression EH = 0.137 TO5 Sha, Poisson's ratio ft = 0.28. Compression testing of cement stone was carried out on cubic samples with ribs of 2 cm; for tension - on samples in the form of figure eights, with a cross-sectional area at the narrowing of 5 cm [31]. For each test, 5 samples were prepared. The samples hardened in a chamber with 100% relative air humidity. To determine the elastic modulus of cement stone and Poisson's ratio, we used the method proposed by millet. K.V. Ruppeneit [_ 59 J . Tests were carried out on cylindrical samples with a diameter of 90 mm and a length of 135 mm.

The solution was supplied into the annulus of the models using a specially designed and manufactured installation, the diagram of which is shown in Fig. 4.3.

In capacity 8 at removed cover 7, cement mortar was poured, then the cover was put in place and the mortar was forced into the annulus of model II with compressed air.

After the intertubular space was completely filled, valve 13 on the outlet pipe of the sample was closed and excess cementing pressure was created in the annular space, which was monitored by pressure gauge 12. Upon reaching the design pressure, valve 10 on the inlet pipe was closed, then the excess pressure was released and the model was disconnected from the installation. During the hardening of the solution, the model was in a vertical position.

Hydraulic tests of three-layer pipe models were carried out on a stand designed and manufactured at the Department of Metal Technology of the Moscow Institute of Economy and State Enterprise named after. I.M.iubkina. The stand diagram is shown in Fig. 4.4, general view- in Fig. 4.5.

Pipe model II was placed into test chamber 7 through the side cover 10. The model, installed at a slight inclination, was filled with oil from container 13 by centrifugal pump 12, while valves 5 and 6 were open. Once the model was filled with oil, these valves were closed, valve 4 was opened and high-pressure pump I was turned on. Excess pressure was released by opening valve 6. Pressure control was carried out with two standard pressure gauges 2, designed for 39.24 Mia (400 kgf/slg). To display information from sensors installed on the model, we used multi-core cables 9.

The stand allowed experiments to be carried out at pressures up to 38 MPa. The high-pressure pump VD-400/0.5 E had a small flow rate of 0.5 l/h, which allowed for smooth loading of the samples.

The cavity of the inner pipe of the model was sealed with a special sealing device, eliminating the influence of axial tensile forces on the model (Fig. 4.2).

The tensile axial forces arising from the action of pressure on the pistons 6 are almost completely absorbed by the rod 10. As shown by strain gauges, a small transfer of tensile forces (approximately 10%) occurs due to friction between the rubber sealing rings 4 and the inner pipe 2.

When testing models with different internal diameters of the inner tube, pistons of different diameters were also used. Various methods and means are used to measure the deformed state of bodies

where ς is a coefficient taking into account the distribution of load and support reaction of the base, ς = 1.3; P pr - calculated external reduced load, N/m, determined accordingly according to the formulas above, for various options backfilling, as well as the absence or presence of water in the polyethylene pipeline; R l - parameter characterizing the rigidity of the pipeline, N/m 2:

where k e is a coefficient that takes into account the influence of temperature on the deformation properties of the pipeline material, k e = 0.8; E 0 — creep modulus of the pipe material under tension, MPa (with 50 years of operation and stress in the pipe wall of 5 MPa E 0 = 100 MPa); θ is a coefficient that takes into account the combined action of base resistance and internal pressure:

where E gr is the modulus of deformation of the backfill (backfill), taken depending on the degree of compaction (for CR 0.5 MPa); P is the internal pressure of the transported substance, P< 0,8 МПа.

Consistently substituting the initial data into the main formulas above, as well as into the intermediate ones, we obtain the following calculation results:

Analyzing the obtained calculation results for this case, it can be noted that in order to reduce the value of P pr it is necessary to strive to reduce the value of P" z + P to zero, i.e. equality in absolute value of the values ​​P" z and P. This can be achieved by changing the degree filling a polyethylene pipeline with water. For example, with a filling equal to 0.95, the positive vertical component of the water pressure force P on the internal cylindrical surface will be 694.37 N/m at P" z = -690.8 N/m. Thus, by adjusting the filling, data equality can be achieved quantities

Summarizing the results of testing the load-bearing capacity under condition II for all options, it should be noted that maximum permissible deformations do not occur in the polyethylene pipeline.

Load-bearing capacity test according to condition III

The first stage of the calculation is to determine the critical value of the external uniform radial pressure P cr, MPa, which the pipe can withstand without losing its stable cross-sectional shape. The value of Pcr is taken to be the smaller of the values ​​calculated using the formulas:

P cr =2√0.125P l E gr = 0.2104 MPa;

P cr = P l +0.14285 = 0.2485 MPa.

In accordance with the calculations using the formulas above, a smaller value of P cr = 0.2104 MPa is accepted.

The next step is to check the condition:

where k 2 is the coefficient of pipeline operating conditions for stability, taken equal to 0.6; Pvac - the value of possible vacuum in the repair section of the pipeline, MPa; Pgv is the external pressure of groundwater above the top of the pipeline, according to the conditions of the problem Pgv = 0.1 MPa.

The subsequent calculation is carried out by analogy with condition II for several cases:

• for the case of uniform filling of the interpipe space in the absence of water in the polyethylene pipeline:

thus, the condition is met: 0.2104 MPa>>0.1739 MPa;

• the same if there is a filler (water) in a polyethylene pipeline:

thus, the condition is met: 0.2104 MPa >>0.17 MPa;

• for the case of uneven filling of the interpipe space in the absence of water in the polyethylene pipeline:

thus, the condition is met: 0.2104 MPa >>0.1743 MPa;

• the same in the presence of water in a polyethylene pipeline:

thus, the condition is met: 0.2104 MPa >>0.1733 MPa.

Checking the load-bearing capacity according to condition III showed that the stability of the round cross-section of the polyethylene pipeline is observed.

As general conclusions, it should be noted that the implementation construction work for backfilling of the interpipe space for the corresponding initial design parameters will not affect the load-bearing capacity of the new polyethylene pipeline. Even under extreme conditions (with uneven backfilling and high groundwater levels), backfilling will not lead to undesirable phenomena associated with deformation or other damage to the pipeline.