How does an underwater gas pipeline work? Laying a gas pipeline along the bottom of the Black Sea is a game of Russian roulette with very sad consequences. Offshore underwater pipelines

There are things that no matter how you talk about them in the most meticulous technological details, they still will not cease to cause admiration bordering on a feeling of miracle. These, of course, include various kinds of megastructures: skyscrapers, bridges, tunnels and, of course, pipelines laid along the seabed.

Welded pipes emerge from the stern of the pipe-laying vessel in a continuous string and are laid on the bottom (photo on the right). The special protection of the installation joints is clearly visible. When the section is completed, a temporary plug is welded to it.

How is it possible to lay hundreds of kilometers of steel pipes at great depths, on a bottom with complex terrain? How to ensure that this entire structure withstands enormous pressure, does not shift, is not destroyed by corrosion, withstands impacts from ship anchors and fishing equipment, and, finally, just works as it should? The most recent example of the construction of an underwater megapipeline was the famous Nord Stream, which ran along the Baltic seabed and connected the Russian and German gas transportation systems. Two strings of pipes, each more than 1200 km long - almost 2.5 million tons of steel, absorbed by the sea by the will of man. Using the example of Nord Stream, we will try to briefly talk about the technologies for creating underwater pipelines.

Welded pipes emerge from the stern of the pipe-laying vessel in a continuous string and are laid on the bottom. The special protection of the installation joints is clearly visible. When the section is completed, a temporary plug is welded to it.

How to wrap steel

The two lines of the gas pipeline consist of 199,755 twelve-meter pipes made of high-grade carbon steel. But since we are talking about contact with such a chemically aggressive environment as sea water, the metal needs protection. To begin with, a three-layer coating of epoxy and polyethylene is applied to the outer surface of the pipe - this is done directly at the manufacturing plant. There, by the way, the pipe is also coated from the inside, however, the task of the internal coating is not to protect against corrosion, but to increase the throughput of the gas pipeline. Red-brown epoxy paint provides a very smooth, glossy surface that reduces as much as possible the friction of gas molecules against the pipe walls.

Is it possible to lay such a pipe on the seabed? No, it needs to be additionally protected and strengthened against water pressure and electrochemical processes. So-called cathodic protection is installed on the pipes (the application of a negative potential to the protected surface). With a certain step, electrodes are welded to the pipes, connected to each other by an anode cable, which is connected to a direct current source. Thus, the corrosion process is transferred to the anodes, and only the non-destructive cathodic process takes place in the protected surface. But the main thing that still needs to be done with the pipe before it is ready to sink to the bottom is concrete coating. In special factories, the outer surface of the pipe is covered with a layer of concrete 60-110 mm thick. The coating is reinforced with steel rods welded to the body, and filler in the form of iron ore is added to the concrete to make it heavier. After concrete coating, the pipe acquires a weight of about 24 tons. It has serious protection against mechanical stress, and the additional weight allows it to lie stably on the bottom.

The photo shows the welding station of the pipe-laying vessel Castoro Dieci. Welded joints will undergo non-destructive ultrasonic testing and then be protected using heat-shrinkable polyethylene sleeve, metal casing and foam. The Castoro Dieci vessel belongs to the Italian company Saipem and is designed for laying pipeline sections in shallow coastal waters. In fact, this is a flat-bottomed, non-self-propelled barge that moves only with the help of a tug and an anchor winch, but Castoro Dieci carries out precise positioning independently due to an eight-point anchor system.

Treacherous bottom

But we must remember that the bottom of even such a relatively shallow sea as the Baltic will not in itself provide a convenient and safe bed for a gas pipeline. There are two factors that the designers and builders of Nord Stream inevitably had to take into account: anthropogenic and natural.

The history of shipping in the Northern European region goes back thousands of years, and therefore a lot of all kinds of garbage, as well as the wreckage of sunken ships, have accumulated at the bottom of the sea. The 20th century made its own terrible contribution: during the world wars, active military operations were carried out in the Baltic, hundreds of thousands of sea mines were installed, and after the end of the wars, ammunition, including chemical ones, was disposed of at sea. Therefore, firstly, when laying the gas pipeline route, it was necessary to bypass identified accumulations of dangerous artifacts, and secondly, to carefully examine the laying area, including the so-called anchor corridor (one kilometer to the left and right of the future route), that is, the area in which they threw anchors of ships involved in construction. In particular, ships equipped with echolocation equipment, as well as a special bottom robot (ROV), connected by cable to the TMS base bottom station, were used to monitor ammunition. When ammunition was discovered (sea mines are very sensitive to movement), they were detonated on the spot, having previously ensured the safety of navigation in a given area and taken measures to scare away large sea animals.

The second factor, natural, is associated with the features of the bottom topography. The seabed is made up of various rocks, it has protruding ridges, depressions, and crevices, and it is not always possible to lower pipes directly onto all this geological diversity. If you allow a large sag in the gas pipeline between two natural supports, the structure may collapse over time with all the ensuing troubles. Therefore, the bottom relief for laying must be artificially corrected.

The stern of a pipe-laying vessel has a stinger—a special groove that increases the bend radius of the laid line. Thanks to the stinger, the letter S takes on a smoother shape.

If it was necessary to level the bottom topography, the so-called rock riprap was used. A special vessel loaded with gravel and small stones, using a pipe, the lower end of which is equipped with nozzles, “targetedly” filled the bottom cavities, giving it a more suitable profile. Sometimes, instead of stones, entire concrete slabs were lowered down. Another option is to dig a trench in the bottom to lay pipes. It is logical to assume that the creation of trenches preceded the laying of pipes, but this did not always happen this way. There is a technical possibility of stabilizing the position of the line at the bottom even when the pipeline is laid (provided that the sea depth at a given point does not exceed 15-20 m). In this case, a trencher with roller grips is lowered from the vessel to the bottom. With their help, the pipeline is lifted from the bottom, and a trench is plowed under it. After this operation, the pipes are laid in the resulting recess.

Laying the Nord Stream using the Castoro Sei vessel
During the pipe-laying process, the Castoro Sei vessel is stabilized by 12 anchors. Each of the anchor ropes is controlled by a winch, which creates a constant tension. The vessel is also equipped with thrusters for more precise positioning.

It is not always possible to pour heavy soil onto the bottom: the mass of gravel pushes through soft rocks. In this case, lighter supports made of metal or plastic structures are used to “straighten” the relief.

Underwater letter

Now, perhaps, the most interesting thing: how do the pipes end up at the bottom? Of course, it is difficult to imagine that each individual 12-meter pipe is welded to a gas pipeline straight into the sea at depth. This means that this procedure must be done before installation. Which, in fact, is what happens on board a pipe-laying vessel. Here it is necessary to briefly return to the design of the pipe itself and note that after applying anti-corrosion protection and heavy-duty concreting to it, the ends of the pipes remain open and unprotected - otherwise welding would be difficult. Therefore, the joint areas are protected from corrosion after welding. First, the installation joints are insulated using a polyethylene heat-shrinkable sleeve, then covered with a metal casing, and the cavity between the casing and the sleeve is filled with polyurethane foam, which gives the joint the necessary mechanical strength.

Next, laying takes place in an S-shape. During the laying process, a scourge welded from pipes acquires a shape reminiscent of the Latin letter S. The scourge emerges from the stern of the ship at a slight angle, drops down quite sharply and reaches the bottom, where it assumes a horizontal position. The hardest thing to imagine is that a string of 24-ton steel pipes coated with concrete is capable of such sharp bends without breaking, but this is exactly what happens.

Of course, in order to prevent the whip from breaking, various technological tricks are used. A stinger stretches tens of meters behind the pipe-laying vessel - a special bed that reduces the radius of inclination of the downward lash. The vessel is also equipped with a tensioning device that presses the pipes downward and reduces bending loads. Finally, the positioning system precisely controls the vessel's position, eliminating jerks and sudden movements that could damage the pipeline. If for some reason the installation needs to be interrupted, instead of the next pipe, a sealed plug with fasteners is welded to the string and the string is “dropped” to the bottom. When work resumes, another ship will pick up the plug with a cable and pull the whip back up.

In 2012, a special “smart probe” was designed that will inspect the condition of the gas pipeline at certain intervals, moving with the gas flow from the Russian Portovaya Bay to the German Lubmin.

Gas pipeline-water pipeline

And yet, it could not have happened without underwater welding. The fact is that each of the Nord Stream lines consists of three sections. The difference between the sections is the different wall thickness of the pipes used. While gas flows from the terminal in the Russian Portovaya Bay to the receiving terminal on the German shore, the gas pressure gradually drops. This made it possible to use thinner-walled pipes in the central and final sections and thus save metal. But it is not possible to ensure the connection of different pipes on board pipe-laying vessels. The sections were joined at the bottom - in a waterproofed welding chamber. To do this, pipe-lifting mechanisms were lowered to the bottom, which were torn from the bottom and precisely positioned the strings of individual sections opposite each other. For the same purpose, inflatable bags with variable buoyancy were used, which ensured vertical movement of the pipes. Thermobaric welding was carried out in automatic mode, but setting up the welding chamber equipment is a complex diving operation. To carry it out, a diving chamber was lowered under water, where a whole team of divers could undergo decompression, and a special bell for descending to the bottom. Welding of sections was carried out at a depth of 80−110 m.

Before using the gas pipeline to pump fuel, it was tested... with water. Even before thermobaric welding, each section of the pipeline underwent severe testing. Seawater, previously filtered from suspended matter and even bacteria, was pumped into the sections using a piston module. The liquid pumped from a special vessel created a pressure inside the whip that exceeded the operating pressure, and this regime was maintained throughout the day. The water was then pumped out and the section of the gas pipeline was dried. Even before there was natural gas in the pipeline, its pipes were filled with nitrogen.

Laying a gas pipeline along the seabed is only part of the Nord Stream project. A lot of effort and expense was required to equip the coastal infrastructure. A separate story is pulling a gas pipeline onto the shore using a powerful winch or creating a mechanism to compensate for the seasonal contraction and expansion of a 1,200-kilometer line.

The construction of Nord Stream has caused a lot of discussion on various near-political topics - from ecology to the excessive role of raw material exports in the Russian economy. But if we abstract from politics, it is impossible not to notice: the trans-Baltic gas pipeline is an excellent example of how advanced technologies and international cooperation are capable of creating modern miracles in a completely working routine mode.

Laying of offshore pipelines can be carried out using several methods. The choice of method for a given water depth is usually determined by a combination of equipment characteristics, availability of equipment to purchase or lease, environmental conditions, cost, and other factors.

1. The most common methods are the following:

For areas where the pipeline is laid in a trench when crossing the coastline:

b dragging to shore from a barge anchored at sea along a pre-designed trench using shore winches.

b installation of strings on shore and pulling the pipeline into the sea along a developed trench using winches of a working barge or tugs.

b installation of the pipeline on a barge and dragging it ashore from the barge along a previously developed trench. The traction force is transmitted from the winch mounted on the barge through a rope passing through a pulley on shore and back to the barge winch.

The latter method is optimal from the point of view of minimizing preparatory work and costs for organizing and operating onshore structures.

2. For laying a pipeline in deep-sea areas:

ь usual S-method;

b laying method for vertical pipes (J-method);

b laying the pipeline from a drum (G-method);

b towing above the bottom;

ь dragging along the bottom;

b towing at a given depth;

b towing on the surface.

Towing methods are usually only used when working on very short pipelines.

For the construction of underwater main oil and gas pipelines, the length of which can reach tens and hundreds of kilometers, the technology of expanding pipelines at sea using special pipe-laying vessels (TPVs) is currently used. In this case, all welding operations, non-destructive testing and application of insulation to assembly joints are carried out on board the vessel at several work stations simultaneously. As the pipeline is extended by one pipe or section, the pipe-laying vessel moves forward, and the pipeline descends to the bottom by free immersion. To ensure a smooth descent of the pipeline from the stern and reduce the resulting stresses, the vessel is equipped with a special supporting device - a stinger. Control of the stress-strain state of the pipeline on the stinger and the freely sagging section between the stinger and the seabed is carried out by applying a longitudinal tensile force to the TUS. The vessel itself is kept in a stationary position using an anchor system or dynamic positioning.

Modern technology for the construction of large-diameter offshore pipelines using pipe-laying vessels is based on the use of two main methods of laying works - the S method and the J-method of pipeline laying. In practice, a combination of both technologies is used, namely, coastal sections are built using ships that implement the S-method, and installation continues deep into the sea using the J-method.

Pipeline installations in deepwater areas can be classified as follows:

1. dragging along the bottom of the sea;

2. diving from the surface of the sea;

3. descent to the seabed from pipe-laying vessels (PLVs).

Laying method by dragging along the bottom

In addition, the dragging method is used in the construction of pipelines to berthless tanker loading points, coastal platforms, or between two oil production platforms at sea.

Efforts are currently being made to develop technology for hauling pipelines over long distances and joining them underwater in hyperbaric chambers. The main problem in this case remains the problem of ensuring the necessary accuracy of laying and joining of each new towed string of pipelines with one already lying on the ground.

The technological process of pipeline construction includes making strings on the shore (500-2000 m long), lowering them into the water and dragging them along the bottom using powerful winches or tugs. The descent path for transporting pipeline strands to the water's edge can have a different design (narrow-gauge rail track with bogies, a descent path made of separate roller supports, an ice descent path, a descent path in the form of a trench filled with water, etc.). In this case, special attention is paid to protecting the insulating coating from mechanical damage. To create the necessary traction, winches are used, installed on tugs or barges, which are supported by anchors.

A head with a device for fastening the cable is welded to the front end of the lash.

The head has a conical or spherical shape, which prevents the head section of the pipeline section from being buried in the ground when pulled through. From the head the cable goes to the traction winch installed on the ship.

To reduce the friction force, the pipeline string is equipped with unloading pontoons, which can significantly reduce the negative buoyancy of the pipeline.

The length of the section (lash) that can be laid at one time depends on its weight and the power of the moving system. The weight of the whip being dragged is the main factor.

The method of dragging pipeline strings along the bottom compared to laying it from a pipe-laying vessel has the following advantages:

b the stress in the pipeline decreases;

b the depth of laying increases;

ь downtime due to weather conditions is reduced.

Sometimes the method of dragging pipes close to the seabed is used.

In this case, pontoons are used, equipped with garlands of chains, which, if their length is chosen correctly, do not allow the pipeline to float to the surface or sink to the bottom.

The pipeline string has zero buoyancy and can be transported using low-power tugs at a distance of 1-2 m from the seabed.

This method essentially coincides with the method of bottom towing of a pipeline when laying it by free immersion.

The dragging method in ice conditions becomes acceptable if the winter ice is stable enough to be used as a working platform, the role of which a ship would normally play.

Rice. 9.1

Method of laying on the bottom by immersion from the sea surface

This method is widely used in the construction of pipelines in coastal areas.

The procedure for carrying out work when laying pipelines involves making strings on the shore, lowering them into the water, towing them afloat to the laying site and lowering them to the bottom. Towing requires favorable hydrological conditions of the region and can be successfully used at the sea depths allowed by calculation with waves of 3-4 points and small currents.

Welding of pipes into a string and their insulation can be carried out according to one of the technological schemes used in field conditions. The lashes are launched in various ways along a narrow-gauge track with carts, roller supports, etc. In some cases, it may be advisable to construct a trench connected to the sea.

The advantage of the method of surface towing of pipeline strings is the possibility of visually checking the correctness of the calculation of the buoyancy of the pipeline and the completeness of its equipment. If conditions on the coastal site do not allow collecting and lowering the lashes into a trench located normal to the water's edge, then the lashes can be collected on beds or racks and rolled into the water along a specially constructed overpass or along an inclined slipway.

Strands up to 15 km long, ready for laying, are towed to the laying site.

The pipeline, whose surface is usually protected by a concrete coating to provide negative buoyancy, is equipped with pontoons to give it positive buoyancy. The finished lash, towed to the laying site in one way or another, is connected to the previously laid end emerging from the water and lowered to the bottom. Depending on the accepted organization of work, the head end of the attached string can be located either on the ship or on the float.

Pipelines of large diameters with positive buoyancy using the surface towing method are towed to the laying site without pontoons. The strands of such pipelines, after connecting to the end of a previously laid strand, are immersed in the bottom by pouring water into it. Water is supplied from the shore end. A quick-release plug with a hose and a cable with a buoy are mounted at the head end of the lowered lash. The buoy records the location of the end of the loop. The pipeline is blown through the hose with compressed air until its head end floats, and then it is supplied for connection to the next towed string. Similar measures should be provided in case of work termination.

Rice. 10.1

With this installation method, the pipeline experiences the greatest bending in sections located near the bottom and surface of the water. To reduce these stresses, in some cases, pipes are filled not with sea water, but with another liquid or solution with the required specific gravity. or a liquid with a lower density (for example, naphtha). Sometimes, to immerse the pipeline, the pontoons are sequentially (usually automatically) disconnected or water is poured into the pontoons, which communicate with each other through a hose.

If the hydrological conditions of the pipeline laying region do not allow towing the pipeline strings on the surface, then the underwater towing method can be used, which involves welding pipeline sections up to 15 km long on the shore and then transporting them under water to the laying site. The launching of the whips into the water is carried out in the absence of rough seas. The entire string of the pipeline is attached to vertical cylindrical buoys located on the surface of the water, so that the string is below the zone of active wave action; for the conditions of the North Sea, this depth is taken to be 40 m.

In this position, the string is towed to its destination, then, using a tug for positioning, the section is lowered to the seabed by remotely flooding the buoys.

During string laying operations, in order to reduce internal stresses, the buoys are unloaded in several stages. To change the position of the pipeline, tension devices installed on the vessel (if used) are used. It is known that when laying steel pipelines without external anti-corrosion coating, problems, as a rule, do not arise. When laying pipelines with a hard coating (epoxy insulation), in practice there were problems associated with the reduced strength of the coating and its dependence on errors in the positioning of the string during transportation and laying on the seabed.

In addition, variations of bottom towing with whips and depth control towing, which is a variation of bottom towing, are sometimes used. This towing method is sometimes called the mid-depth laying method.

During bottom towing, pontoons and chains are attached to the pipeline. The overall buoyancy of the system is calculated in such a way that the pipeline floats above the seabed, and part of the chain (load) is on the seabed. This method provides stability against the effects of waves and currents, but there is a limitation in its use due to the fact that the seabed must be sufficiently smooth and level.

When towing with depth control, the buoyancy of the system must be calculated with such accuracy that the lifting forces acting on the weight chains due to towing at a certain speed would lift the pipeline from the seabed. When towing stops or the towing speed drops below a critical value, the pipeline seems to hang above the bottom. Using this method, several sections of pipelines with a diameter of 660 mm and a length of 3.5 km have already been towed and subsequently laid in waters 150 m deep.

When comparing the method of constructing underwater pipelines, based on bottom towing of pipeline strings with subsequent control of the lowering depth, with the traditional method involving the use of a pipe-laying vessel, its following advantage is clear: a minimum of machinery and equipment is required (only a leading tug with a control system and one or two vessel for collecting buoys. The method is economical, especially effective for underwater laying of insulated pipes, heated pipes or a bundle of pipelines in a common shell (pipe).

Surface towing

Underwater towing

The considered method of near-bottom towing of pipes with their subsequent laying on the bottom is applicable to almost all types of pipelines that were previously constructed in the traditional way using a pipe-laying vessel. The immersion operation also does not present any particular difficulties and is not a limiting factor for using the method. If necessary, buoys can be unloaded in two or more stages in order to reduce internal stresses in the pipeline during towing and laying operations. To change the position of the pipeline, a device for tensioning it is required, and in the case of laying steel pipelines without an anti-corrosion coating applied on top, no problems arise, but when laying pipelines with plastic insulation, some problems may arise. The length of pipeline strings (sections) directly depends on the positioning operation. If the current is more or less moderate, then even very long pipelines can be accurately positioned. If track conditions allow, the length of the lines (sections) can be increased.

Descent to the seabed from pipe-laying vessels (PLVs)

A. Installation in horizontal or slightly inclined position

The most common method for laying pipes using this method is the so-called S-method. To ensure a smooth descent of the pipeline from the stern, the vessel is equipped with a special launching device - a stinger. The section of the pipe located between the point of contact of the bottom and the stinger takes the shape of an S-shaped curve, and therefore this method of installing underwater pipelines is called the S-method.

Rice. eleven.

This method uses the following container pipelaying technology:

From the ship's warehouse, pipes are supplied to the auxiliary installation line using a low-capacity mobile crane;

On the auxiliary pipe assembly line, the protective shells from the ends of the pipe are dismantled, the pipe cavity is cleared of foreign objects and the edges are cleaned for incoming inspection of the pipe ends, the incoming inspection of the pipe ends is carried out, centered (at the same time, the edges of both pipes are also deovalized before welding and welded in a section of two or three pipes, and the quality of welding is checked by means of radiographic or ultrasonic testing;

The pipe sections are moved to the main assembly line using a cross conveyor;

At the 1st work station (station) of the assembly line, the pipe section is joined to the pipeline, centered and the main weld is applied;

The pipe-laying vessel moves along the route for the length of the section, the junction of the section and the pipeline moves to the 2nd station, where subsequent layers of the weld are applied, then to the 3rd, 4th and subsequent welding stations. Depending on the technology adopted, the number of welding stations per lines can range from 3 to 6;

The junction of the section and the pipeline, as a result of the vessel moving along the route, gets to the post of non-destructive testing of the weld, then to the post for cleaning and insulating the joint and then to the post for concreting the joint (if provided for by the technology), then the pipeline is drained of water.

The S-method has the following advantages and disadvantages:

Advantages:

· suitable for work in shallow and deep waters;

· less dependent on weather than for tugs or winch barges used for towing or pulling;

· high productivity compared to the J-method;

· several vessels operating using this method can be found in any area of ​​the world (their number increases as the water depth decreases), which leads to lower mobilization and demobilization costs, since the vessel can be found in the area where the work is being carried out.

Flaws:

· possibility of damage to the stinger by wave impacts;

· since the pipeline passes through the surface of the water at a relatively small angle, a fairly long section is close to the surface and exposed to waves;

· the laying support team is more expensive than a tug or winch barge;

· TUS cannot turn in the wind when laying;

· high tensile loads limit the working depth.

During the laying of offshore pipelines, butt welded joints of pipes are loaded to a much greater extent than onshore ones, and therefore the requirements for their welding are increased. However, due to the high cost of the pipe-laying vessel (and other technical and technological reasons), a high speed of pipeline production is required. In connection with this, the most advanced automated welding installations are usually used for offshore pipelines, allowing welding to be carried out from the inside of the pipe.

The auxiliary assembly line includes devices for moving pipes and sections, a machine for preparing edges for welding, a coating quality detector and an external or internal centralizer, welding equipment, a welding quality control device, a joint isolation device and a means for inserting and repairing a defective section of the seam.

In addition to the equipment listed, the main installation line includes a tension device and means for concreting the joint. On modern pipe-laying vessels, as a rule, concrete coating is not carried out, and the joint is insulated with a layer of bitumen, polyethylene tape or heat-shrink sleeve.

Modern pipelaying vessels operating using the S-method are capable of laying pipelines with a diameter of up to 56" (1417 mm) to a depth of 300 m, and with a diameter of 32" (810 mm) to a depth of up to 700 m at a speed of 3-5 km/day.

The considered S-method for installing offshore pipelines has a limitation on water depth, because the horizontal force of the pipe-laying vessel may not be enough to create the required stress-strain state of the pipeline. At the same time, an increase in the radius of curvature and the total length of the stinger complicates control over the laying of the pipeline and makes it vulnerable to the effects of waves and currents.

Typically, a powerful anchor system is used to hold the TUS in a given location and move along the route of the pipeline being laid (with severe restrictions on movement under the influence of wind, waves and currents). For the operation of the anchor system, it is of great importance to ensure the holding force of the anchors on the ground.

In addition to the anchor holding system, the dynamic positioning system is widely used.

Advantages of dynamic positioning of a pipelay vessel:

· absence of any danger of damage to existing submarine cables and pipelines;

· less mutual interference in case of other operations near the TUS;

· ability to work within the anchor area of ​​drilling rigs and moored vessels;

· flexibility in choosing the place for lowering and laying pipes on the bottom;

· quick descent and laying of pipes to the bottom;

· quick stop to the bottom in case of worsening weather conditions;

· no downtime due to restrictions in the placement of anchors in adverse weather conditions;

· reduction of downtime as a result of mechanical damage;

· ability to work with continuous vertical pumping during pipe-laying operations.

The disadvantage of dynamic positioning is the deep draft of the vessel, equipped with an azimuth propulsion unit located approximately 4 m below the keel; approach to the shore is impossible, since a water depth of at least 15 m is required.

B. Vertical installation

Currently, when constructing pipelines at great depths, the J-method, also named after the shape of the curve that the pipeline takes during the installation process, is increasingly used.

The main features of the J-method are that for joining and centering a section of pipes with a pipeline, a lift is required to deliver the section to an inclined platform (launch ramp); the pipeline is connected to the section at one work station using a welded, coupling or connector connection; The pipeline is lowered directly from the side or stern of the vessel without the use of a stinger, due to the fact that the upper end of the pipeline is located vertically.

The advantage of this method of pipeline installation is the possibility of using significantly smaller vessels, without the use of bulky stingers.

If the S-method has an upper limit on depth, then the use of the J-method, on the contrary, is limited by the minimum depth.

Rice. 12.

The J-method is primarily used for laying large-diameter pipes at relatively large depths and involves lowering the pipeline in a vertical (or near-vertical) position from a vessel equipped with a dynamic positioning system. Using this method, the pipeline string comes off the STS, hanging like a cable and bending slightly towards the horizontal only as it approaches the seabed.

In this case, the tension acts in a nearly vertical direction, virtually eliminating any horizontal reaction of the equipment placed on the vessel. In this way, the bend at the top is completely eliminated and a very short stinger is sufficient to guide the string of pipes over the side of the vessel and relieve stress on the laying interval.

The pipeline is welded from 4 pipe strands in a vertical position in an assembly tower or derrick installed on the TUS, and laid on the bottom with tension to control bending stresses. The vessel moves forward and the laying continues, constantly adding new strands to the pipeline. Installation of the lashes into a vertical position on the assembly tower is carried out using a rotary ramp.

The step-by-step technology for laying a pipeline using the J-method is as follows:

First stage.

The whip with cut edges is loaded from the rack onto the rotary ramp using two deck cranes. The lashes are fixed on the rotary ramp by means of a set of rollers, after which they are raised until the angle of their inclination is equal to the angle at which the finished pipeline is held on the stinger, descending from the stern and held by the devices.

Second phase.

The lash is centered using an internal centering tool suspended from the top of the turning ramp.

Third stage.

The welding of the joint is completed. Non-destructive testing has been performed. The vessel begins to move to a new position, and the joint is lowered to the level of the coating station.

Fourth stage.

A coating is applied to the joint. The vessel begins to move to a new position, and the pipeline descends through the stern into the sea until its free end approaches the welding station. The turning ramp is lowered and the first stage is repeated.

With this scheme, only one station is usually used for welding, inspection and coating of joints, so the productivity of the J-method is less than when working with the S-method. However, this method has the advantage that when laying large diameter pipelines in deep waters, much less tension is required than when laying the S-method.

The J-method vessel is equipped with a dynamic positioning system, since it is difficult to use anchors at great depths (up to 3000 m), which require the use of the J-method.

The J-method has the following advantages and disadvantages:

Advantages:

Large working depth;

Typically less tension is required due to the larger vane angle than using the S-method in deep water (slack section instead of kink section),

Lower stresses due to the absence of bending (a long stinger and equipment design that leads to excessive bending of the pipeline are not used, but with a rigid vertical ramp, a short vertical stinger with a socket must be installed under it to limit the bending moment acting on the pipeline);

Less effort is required to position the SUT;

Less sensitivity of a pipe passing through the surface of the water to the effects of waves;

Less dependent on weather than tugs or winch barges used for towing or hauling;

Easier descent, laying, temporary lowering of the pipeline to the bottom and subsequent lifting,

Fewer spans at the bottom and shorter span lengths due to lower residual tensile stresses;

Makes it possible to lay a pipeline along a complex route, in order to bypass an obstacle or to fulfill the requirements associated with the operational system;

The use of multi-pipe braids manufactured onshore provides excellent quality control as most girth welds are completed onshore under controlled environmental conditions.

When the pipes are in a vertical position, the J-method has some other advantages:

- much less sensitivity to weather conditions, since the vessel can turn with the wind;

b lower mobilization costs for vessels with small or rigidly fixed cargo booms.

Flaws:

Limited number of vessels operating using the J-method;

Existing vessels operating using the J-method are designed for insufficiently large diameter pipes, which leads to increased mobilization and demobilization costs when it is necessary to modernize the barge to work with large-diameter pipes;

Low productivity compared to ships operating using the S-method;

TUS costs more than a tug or winch barge.

B. Unwinding from the drum

For the construction of flexible or steel pipelines of small diameter, the unwinding method from a drum is used, which in the specialized literature is called the G-method.

The principle of maximizing onshore work time to minimize costly offshore work time, which is common to all subsea construction and operation processes, also applies to the G-method, in which a long string of welded, insulated and hydraulically tested pipeline is fabricated onshore and spooled onto large diameter drum.

During laying, the pipeline, which has been plastically deformed during the coiling process, is rolled out using a straightening device to “straighten” the curvature, after which it lies on the bottom as the vessel moves forward.

The advantage of this method is faster installation in offshore conditions than can be achieved using conventional pipelay vessels. In addition, it is also possible to reel several pipelines on the drum at the same time and thus install several lines of smaller diameter at once before the vessel with the drum returns to the port for reloading.

When reeling a pipeline from a drum located horizontally or vertically on the deck, the following technology is used:

· at the onshore base, the pipes are welded into a pipeline using traditional technology;

· as the pipeline grows, it is wound onto a drum at a speed of up to 1.0 km/h. Winding is carried out through a bending mechanism, which gives the pipeline a preliminary curvature. The stresses arising during this process do not exceed the stress in the pipeline during installation;

· a removable drum with a pipeline is installed on the deck of the pipe-laying vessel. If the drum is installed permanently on the ship, then the pipeline is wound on a ship moored at the coastal base where the pipeline is being built up;

· the pipe-laying vessel goes to the pipe-laying area;

· the end of the pipeline is attached to the riser (riser) of the platform or welded to the end of an already laid section of the pipeline;

· The pipe-laying vessel moves along the route and lays the pipeline.

Unwinding from the drum, the pipeline passes through a straightening device and, along a roller track, descends through an inclined slope at the stern end of the vessel into the water.

The tensile force required during laying is created by the joint work of the ship's tensioner and the drum drive mechanism. Sometimes a braking device is installed on the ship to prevent spontaneous unwinding of the pipeline from the drum.

Laying from a drum allows the pipeline to be lowered into the water at an angle close to a straight line, which eliminates the need for stingers.

The main technological equipment of drum-type pipelay vessels includes a tensioner, a straightening device and a drum with pipeline.

When using this method, ovality and plastic deformation of pipes are often observed, which excludes the possibility of their concrete coating and limits the diameter. The pipes must have sufficient mass to ensure their immersion and stability at the bottom. Typically, the diameter of drums laid from ships to ensure the necessary negative buoyancy without weights is limited to 400 mm.

Rice. 13. Drum method: 1. Vessel. 2. Pipeline. 3. Drum. 4. Special trigger device.

Currently, the “drum” method of laying pipelines is widely used when installing pipelines made of elastic materials. It is known that pipelines constructed from elastic (flexible) pipes are simpler, cheaper, and more reliable than steel pipelines. Typically, flexible pipelines are used in field piping systems because they transport corrosive reservoir products, or as risers.

A flexible pipe with steel reinforcement is a composite structure made of layers of materials that defines a pressure channel. This pipe design allows large bending deformations without a significant increase in bending stresses. Another advantage of underwater pipelines made of elastic materials is that it can be easily dismantled.

Flexible pipes are reinforced in the axial and radial directions using steel cores, flat reinforcing elements, spirals, and cylindrical frames.

The international community recognizes the indisputable fact of the Russian Federation’s ability to lay a pipeline along the seabed and successfully begin its operation. Success has been achieved in the implementation of the Nord Stream project in the Baltic Sea.

Next in line is South Stream, but the water area is narrower than the Black Sea. Is the Russian Federation capable of building a gas pipeline with performance indicators that will ensure its trouble-free operation throughout its entire lifespan? Yes! Capable. Russian specialists will ensure the functioning of the pipeline even until the moment when natural gas reserves are exhausted. At that time the pipe will be empty as there will be no gas.

So what does Russian roulette have to do with it? There are a number of circumstances that no one has the right to ignore.

1. Hydrology of the Black Sea

a) the depth of most of the seabed is 2000 meters.

When diving to a depth of 10 meters, we have an increase in pressure of 1 atmosphere. The nuclear submarine on which the author had the honor to serve dived to a depth of 415 meters. The thickness of the armor from which the Murena was made was 5 cm. We did not stretch the threads between the bulkheads; this is technologically impossible to do, but we visually recorded the “subsidence” of the missile silos, and the “moaning” of the durable hull of the boat was perceived as a continuation of our own exposed nerve.

b) the volume of water in the Black Sea is 550,000 km3.

c) hydrogen sulfide H2S is present in 87% of the volume of the entire sea and in a free state will fill 20,000 km3.

d) the length of gas pumping from a station on the coast of the Caucasian coast of the Russian Federation to a station on the Bulgarian coast is several hundred kilometers. There is no technical possibility of additional “acceleration” of the gas flow at the intermediate station. The only option is to increase the pressure as much as possible on the territory of the Russian Federation and pump it from the pipe on the other side. (Very important point!)

2. Insurmountable circumstances that no one can influence

Due to a storm, the ship was wrecked. The craft sinks and ends up on a gas pipeline. 15,000 tons of metal receive enormous energy until they overcome 2,000 meters from the surface to the bottom. The pipeline will be cut instantly. Common practice in the Black Sea is to transport scrap metal on flat-bottomed (!) river vessels, which have a reinforced hull and are classified as “river-sea”. You can also weld something to the hull of a self-propelled river barge and raise its class to the “river-ocean” level, but this will not save you from an immediate catastrophe... Then it will be like this: under crazy pressure, the gas forms a bubble that will go to the surface. The inertial forces in the gas pipeline (see paragraph above), the time required to activate the emergency system and shut off the flow, will make it possible to overcome incredibly large volumes of water saturated with hydrogen sulfide and break through a 100-400 meter layer of oxygen-enriched water. During bad weather, when a ship accident occurs, lightning is always present. A mixture of gas, hydrogen sulfide and atmospheric oxygen will not wait long for a spark that will trigger an explosion.

3. Let's pray for the souls of the innocent people killed in Beslan and Norway. Children died at the hands of terrorists, young people died on a tiny island at the hands of a madman.

The pipeline at the bottom of the sea can be seen on the device as clearly and clearly as your own slippers on outstretched feet. A HEAT shell burns through a tank's armor like newsprint, and the tank's armor is much thicker than a pipe wall. A gas pipeline along the bottom of the Black Sea is a grenade that can be blown up by insurmountable circumstances and by any madman, fanatic or individual terrorist. And the organization of bad guys will carry out such a terrorist attack even at night.

The consequences of a hydrogen sulfide explosion can lead, in the worst case scenario, to the loss of orbit by planet Earth or shift tectonic plates - then we will lose 60% of fauna and flora. A certain period of time will pass and life will return and flourish - the main thing is that Gazprom does not revive.

Over the 20 years of Ukraine’s independence, we have not had a leadership that did not “cheat” with the gas transportation system. Means, colossal means, cloud the minds of everyone, everywhere. The opacity of relationships, shadowy schemes - this is what leads to such projects and can put an end to civilization. Such relations between Ukraine and the Russian Federation are unacceptable.

You can’t blame the Russian Federation for all its sins, making Ukraine white and fluffy. Both parties must be held accountable. And the arbiter in this situation should be the world community. The Ukrainian gas transportation system must be operated in a regime of openness and international audit and constant monitoring. And the first step towards this is that the international community must put an end to possible fraud in the elections to the Verkhovna Rada of Ukraine in 2012. Today, officials of the current government can buy floating drilling platforms at a higher price than the manufacturer sells them for. Our leadership leaves no choice for the Russian Federation but to start building South Stream. Such management cannot honestly operate the Ukrainian gas transportation system. It must go away. The world community must realize the scale of the threat of Ukrainian corruption and the stubbornness of Gazprom, which together can create conditions for an explosion that could easily surpass the simultaneously detonated US nuclear potential.

The development of oil and gas fields located on the shelf is impossible without the construction of pipelines. In modern offshore oil fields, some underwater pipelines connect individual offshore platforms with a central storage tank and a floating berth, which is equipped for mooring tankers, while others connect storage tanks directly to an onshore oil storage facility.

The technology for constructing offshore pipelines involves the following stages: excavation, preparation of the pipeline for laying, its laying, backfilling and protection from damage.

The need to bury offshore pipelines is due to the fact that otherwise they may be damaged by the movement of coastal ice, trawls, ship anchors, etc. When excavating, devices are used that develop a trench, both from the surface of the water and in a submerged position. The former include floating dredgers, hydraulic monitor units, grab dredgers, pneumatic and hydraulic soil pumps. The second includes various kinds of autonomous devices operating under water.

Thus, in Italy, the S-23 dredger was created, which can develop trenches at a depth of up to 60 m. Trench digging is carried out with a milling ripper at a speed of up to 130 m/h in medium-density soils. The parameters of the trench being torn off are as follows: depth - up to 2.5 m, bottom width - from 1.8 to 4.5 m.

In Japan, a bulldozer and an excavator have been developed to carry out work underwater at a depth of up to 70 m. The bulldozer weighs 34 tons, has a powerful engine and moves on tracks. Unlike dredgers, it can mine dense soils.

The underwater excavator is designed to develop trenches during the construction of offshore pipelines, foundation pits for various offshore structures and dredging operations. The speed of its movement along the bottom is 3 km/h. The excavator is controlled by two operators from a surface vessel.

Before laying, a protective coating is applied to the pipeline and it is loaded against floating. World experience in the construction of offshore pipelines has shown that the best protective coating for them and at the same time a weight bearing is a concrete coating.

Laying of offshore pipelines is carried out by dragging, or from the sea surface by gradual build-up.

The drawing diagram is shown in Fig. 4. Pipeline 1 moves along a roller descent track 5. The traction force along the cable 2 is transmitted from a winch installed on the vessel 3. The vessel is held by anchors 4. The pulling method is simple and ensures that the pipeline is laid exactly along the route. However, it is applicable when laying pipelines up to 15 km in length.

The scheme of laying from the sea surface with a gradual build-up (Fig. 5) has become most widespread. The pipe-laying vessel 4 is secured to anchors 6, each of which can withstand a force of up to 10 tons. A stock of concrete-lined pipes is created on the vessel, sections of which are 36 m long and delivered by special transport vessels. The length of the pipe-laying vessel allows the sections to be connected into a string 180 m long.

Pipeline 1 is laid as follows. On vessel 4, the next string is welded, the joints are insulated, concreted and equipped with floats 2. The string is joined to the end of the pipeline laid earlier and held by a tension device and a special rigid attachment 3. The angle of inclination of this attachment is selected so as to minimize the stress in the lowered pipeline. The joint is insulated and concreted, after which the lashes are lowered into the water on pontoons. The pontoons are unslinged automatically at a given depth.

The vessel "Suleiman Vezirov" with a displacement of 8900 tons can lay 1.2 km of welded pipes with a diameter of 200...800 mm under water per day. The Vyartsilya pipe-laying vessel with a displacement of 41,000 tons allows laying up to 2.5 km of pipeline with a diameter of 530 mm per day at a depth of up to 300 m. The supply of pipes is enough for them to work for 5... 10 days.

Laying offshore pipelines with preliminary trenching is associated with significant costs. Laying a trench at sea costs a hundred times more than on land. In addition, it is quite difficult to accurately lay a pipe in a trench from the side of a ship rocking on the waves.

It is cheaper and easier to bury a steel pipeline already laid to the bottom into the ground. For this purpose, special underwater pipe-deepening units have been designed. Their main element is a cart that rolls along a pipe.

Fig 4 - Pipeline pulling diagram: 1 - pipeline; 2 - cable; 3 - vessel on which the winch is installed; 4 - anchors.

Fig 5 - Scheme of laying a pipeline using a pipe-laying vessel: 1 - pipeline; 2 - floats; 3 - rigid attachment on which the end of the pipeline rests; 4 - pipe-laying vessel; 5 - tap; 6-anchors.

Various deepening devices are attached to the trolley: hydraulic jet nozzles, plows, cutters or rotary wheels. The energy to drive them is supplied from the ship via a cable line that reaches a length of 1 km or more. Recently, pipe plungers have been equipped with underwater television cameras, which makes it possible to monitor their operation from the surface.

Rock riprap is most commonly used to protect offshore pipelines from damage in coastal areas. The stone is dumped from the side of barges with inclined bunkers and vibrators. Vessels with a smooth deck are often used, over the side of which a bulldozer throws stones. The accuracy of such filling is low. Therefore, at present, the role of a bulldozer is performed by special shields, which are controlled by hydraulic cylinders connected to a computer. Such devices make it possible to efficiently backfill a pipeline with waves the height of a two-story building and wind speeds of up to 15 m/s.

Another way to protect offshore pipelines from damage is to lay asphalt over the trench. The seabed is asphalted using a floating asphalt plant. From its deck, the finished mixture is fed to the bottom through a vertical pipe, in the center of which there is a heater pipe so that the asphalt does not have time to cool due to contact with relatively cold water. At the bottom, the asphalt is leveled and rolled by an automatic device similar to those used for paving squares and streets. In one pass of the paver, a paved area 5 m wide and 85 mm thick appears at the bottom.

Pipeline transport in Russia, with almost 100 years of history, is the largest in the world. However, offshore pipelines (OPPs) are used relatively recently. Offshore sections of gas pipelines were built and put into operation: North European (Nord Stream or NEGP) in the Baltic Sea, Blue Stream and Tuapse-Dzhubga in the Black Sea. Offshore oil pipelines of relatively short length are available in the Pechersk Sea (export pipeline of the Varandey oil terminal), in the Baltic (D-6 field) on the Sakhalin shelf. MT from the Shtokman gas condensate field in the Barents Sea and the Kirinskoye gas condensate field on the shelf of Sakhalin Island, and South Stream in the Black Sea are in the design stage. In the future, as work on the Arctic shelf develops, a significant increase in the number of MTs should be expected. The operation of pipelines, in relation to the operation of pipelines on land, has certain specifics, which are not sufficiently reflected in the regulatory documentation in force in the Russian Federation. Issues of ensuring the safe operation of these pipelines are currently being resolved mainly on the basis of projects focused primarily on in-line diagnostics. This principle does not meet modern requirements for the reliability and safety of hazardous production facilities. Only a systematic approach focused on the full-scale implementation of the task of monitoring MT in real time, as well as timely and high-quality implementation of inspections, maintenance and repair work can guarantee the safe operation of MT in the conditions of the Arctic shelf. What steps need to be taken today to ensure this approach?

Features of offshore pipelines

During design and construction, the reliability and safety of MT are ensured according to increased requirements in relation to those laid on land. This is caused by special (sea) conditions, such as a fairly aggressive marine environment, underwater location, increased length without intermediate compressor stations, the effects of sea waves, wind and currents, seismicity, complex bottom topography, limited possibilities for preparing and monitoring the route, difficulty or impossibility implementation of standard maintenance and repair regulations for main gas pipelines, etc.

The following can be specified as special measures to ensure the safety of transport vehicles:

1. installation of security zones along the MT route (at a distance of up to 500 m from the pipeline axis) with a special regime for navigation and economic activity, determined at the federal level;
2. ensuring protection of MT from corrosion, which largely determines its reliability and safety, for the entire period of its operation and only comprehensively (external and internal coating and cathodic protection means);
3. the use in the MT design of insulating connections with a corrosion protection system (flange or coupling) from land areas;
4. When designing the MT, taking into account all possible impacts on the pipeline that may require additional protection, namely:

The occurrence and spread of cracking or collapse of pipes and welds during installation or operation;

Loss of mechanical properties of pipe steel;

Unacceptably large pipeline spans at the bottom;

Seabed erosion;

Impacts on the pipeline by anchors of ships or fishing trawls;

Seismic impacts;

Violation of the technological regime of gas transportation.

1. when designing the MT, performing an analysis of the permissible spans and stability of the pipeline on the seabed, as well as calculating nozzles that limit the avalanche collapse of the pipeline during its laying at great depths of the sea;
2. deepening of the MT into the bottom in areas where it comes ashore below the predicted depth of erosion of the bottom of the water area or the coastal section for the entire period of operation of the offshore pipeline;
3. laying of MT on the surface of the seabed only if its design position is ensured during the entire period of operation (the possibility of its floating or moving under the influence of external loads or damage by fishing trawls or ship anchors is excluded); if necessary, the bottom of the water area is pre-prepared or the pipeline is laid in a trench ;
4. choosing a method of protecting the pipeline depending on local environmental conditions and the degree of potential threat of each impact on the gas pipeline;
5. designing the MT to be free from obstacles to the flow of the transported product (in the case of using artificial bending curves or fittings, their radius is taken to be at least 10 pipeline diameters, which is sufficient for the free passage of cleaning and control devices).

To ensure the safety of hydrocarbon transportation and reduce risk in the design and construction of underwater pipelines, the most modern achievements in the field of their construction, increased industrial safety requirements, high-quality pipes, welding and insulating materials, control systems, etc. are used. This circumstance objectively creates conditions for increasing the reliability and safety of transport vehicles, which is confirmed by the absence of accidents on all transport vehicles put into operation in our country. However, the accident rate on offshore pipelines is a real fact and must be taken into account during the design, construction and operation of each pipeline.

Accidents on offshore pipelines

Data on accident rates on offshore pipelines are quite widely presented in available sources of information. For example, they are published by the US Department of Transportation Office of Pipeline Safety (OPS) (oil, gas pipelines) as well as relevant organizations of the European Community. Based on an analysis of available data on approximately 700 cases of emergency depressurization of underwater pipelines (over an approximately 40-year period), the main causes of their destruction were established.

Distribution of the total number of destructions of underwater pipelines depending on the causes that caused them

The dominant causes of emergency situations are: corrosion - 50%, mechanical damage (impact of anchors, trawls) of auxiliary vessels and construction barges - 20% and damage caused by storms, bottom erosion - 12%. Moreover, the majority of incidents occurred in MT sections in the immediate vicinity of platforms (within ~15.0 m), including on risers.

Based on the analysis of statistical data on the accident rate of offshore pipelines, it was revealed that taking into account the measures taken to improve the reliability and safety of pipelines, the intensity of accidents on offshore pipelines has been constantly decreasing and is currently in the range of 0.02 - 0.03 accidents per year per 1000 km of their length.

For comparison, in the initial period of MT use (70s - years of the last century), the accident rate on offshore pipelines in the Gulf of Mexico was 0.2 accidents/year/1000 km of pipelines and 0.3 accidents/year/1000 km in the North Sea.

For comparison, in Russia the average frequency of accidents is 0.17 accidents/year/1000 km for gas pipelines and 0.25 accidents/year/1000 km for oil pipelines.

When operating MTs, despite the safety measures taken, there are real threats of damage or malfunction. These threats include pipeline defects, abnormal technological processes and modes, man-made hazards, processes and phenomena in the geological environment, natural, climatic and geological factors, actions of third parties, scientific, industrial, military activities in the areas where MT is located and other reasons.

Danger level of offshore pipeline accidents

Accidents of offshore pipelines create a danger of disrupting the ecological balance of the marine and geological environments in the areas of their use. The degree of danger of accidents increases significantly in the Arctic and Far Eastern seas of Russia, which are characterized by a low level of intensity of natural biological treatment, which in the event of emergency oil spills can lead to long-term pollution of sea water and bottom sediments.

In the event of an accident on an offshore pipeline, environmental damage will be determined by the amount of payments for excess environmental pollution and the cost of work to localize and eliminate the emergency spill. In offshore leakage conditions, due to the lack of a reliable leak detection system, as well as the complexity of the work to eliminate emergency oil spills at sea, leaks can be expected with significantly higher values ​​than the average for existing onshore pipelines.

The reality of MT accidents, the degree of their dangers, limited experience and possible risks of MT operation require adequate safety measures, which, in accordance with the requirements of the Federal Law of December 27, 2002 No. 184-FZ "On Technical Regulation", must be reflected, first of all, in approaches to organizing the operation of MT.

Analysis of foreign experience in regulating the operation of offshore gas pipelines

Quite strict regulation of the operation of offshore pipelines has been established abroad. The main documents from among the generally recognized international standards (published in the USA, Great Britain, Norway, the Netherlands, etc.) are listed in the table.

In Europe, regulation of the operation of offshore gas pipelines is implemented in the form of European Union Directives, which are approved by members of the European Union. In this case, the method of reference to existing special regulatory documents on main sea pipeline transport, which have received a positive assessment based on the results of long-term use (approximately 20 standards of the ISO series, standards of the USA, Norway, Canada, etc.), is widely used, such as:

API - 1111 "Design, construction, operation and repair of offshore pipelines for hydrocarbons", Practical recommendations. 1993 (US standard);

Det Norske Veritas" (DNV) "Rules for Subsea Pipeline Systems", 1996 (Norwegian standard);

BS 8010. "Practical Guide for the Design, Construction and Laying of Pipelines. Subsea Pipelines." Parts 1, 2 and 3, 1993 (British Standard);

US Standard ASME B 31.8 "Standards for Gas Transportation and Distribution Pipeline Systems", 1996;

US standard MSS-SP - 44 "Steel flanges for pipelines", 1990.

ASME B31.4-2006 Pipeline systems for the transport of liquid hydrocarbons and other liquids;

ASME B31.8-2003, Gas Piping Systems and Gas Distribution; -CAN-Z183-M86 "Oil and gas pipeline systems";

ASTM 96 "Abrasion Resistance of Pipeline Coatings."

The standards used most often are from Det Norske Veritas (DNV). In particular, on their basis, the offshore section of the NEGP was created and a gas pipeline from the Shtokman gas condensate field was being designed.

The DNV standards system relates safety to the elimination of the threat of harm to personnel, property and/or the environment, and risk to the extent of damage caused. This approach is focused on balancing actions to manage operational and technological risks to find a sustainable balance between safety, functionality and cost.

The requirements apply to pipeline inspections and repairs. At the same time, the basic provisions of inspections and control must be established, based on detailed programs, the principles of the formation of which are revised after 5-10 years.

In accordance with section B 200 of the DNV standard, the pipeline system must be subject to routine monitoring (inspection) during operation. DNV standards require inspection of the structure of offshore pipelines and detection of defects (section 10, paragraph B, E DNV-OS-F-101), inspection and control of external and internal corrosion (section 10, paragraph C, D DNV-OS- F -101).

However, “Parameters that may threaten the integrity of the pipeline system must be monitored and assessed at a frequency that allows corrective action to be taken before the system is damaged.”

In general, the provisions and requirements set out in DNV standards are advisory in nature and do not contain specific provisions on techniques and technologies for solving them.

Regulatory regulation of the operation of offshore pipelines in the Russian Federation

Based on the results of the review and analysis of the current regulatory framework regarding the requirements of federal authorities and supervisory authorities for the organization and performance of work on the inspection, operation and repair of offshore sections of gas pipelines, the following can be noted.

1. Currently, the entire existing regulatory framework for construction is being updated by updating SNiP and GOST, introducing European Union standards, as well as creating a unified regulatory framework for the Customs Union of Russia, Belarus and Kazakhstan and EurAsEC.

2. Pipeline operators have the opportunity to form their own regulatory framework that does not contradict federal legislation, both by developing new documents and by recognizing existing regulatory documents - Russian and international.

3. In the Russian Federation, general requirements have been established to ensure the safety of offshore pipeline transport of oil and gas through the appropriate organization and procedure for carrying out work on their inspection, operation and repairs. There is no detailed regulatory and technical documentation regulating the organization, conduct and control of this work at the federal level, since it is assumed that it will be developed at the level of organizations and enterprises.

4. The legal basis for the operation of MT is Federal Law No. 187-FZ of November 30, 1995 and Decree of the Government of the Russian Federation of January 19, 2000 No. 44. In accordance with these documents, the MT operation system must be created and operate in compliance with the requirements stipulated by water legislation , and in the manner established by the Government of the Russian Federation, as well as on the basis of the regulatory and technical documentation (NTD) in force in the Russian Federation, internal regulatory documentation of the EO (branch of the EO), as well as international standards recognized in the Russian Federation.

5. In the Russian Federation, in the field of design, construction and operation of offshore pipelines, the regulatory documents specified in the table are applied. In practice, international standards are widely used:

ISO 13623, ISO 13628, ISO 14723-2003;

DNV standards, including Marine Operations Planning and Execution Regulations;

CAN/CSA-S475-93 (Canadian Standards Association) standards. Naval operations. Marine structures;

German Lloyd. Rules for classification and construction. III. Marine technology.

In addition to those indicated in the table, there are about 70 other regulatory documents related to various aspects of the MT life cycle.

6. The main document operating at the state level is GOST R 54382-2011 Oil and gas industry. Subsea pipeline systems. General technical requirements (hereinafter referred to as GOST), which establishes requirements and rules for the design, manufacture, construction, testing, commissioning, operation, maintenance, re-examination and liquidation of underwater offshore pipeline systems, as well as requirements for materials for their manufacture. GOST is a translation from English into Russian of the Norwegian standard DNV-OS-F101-2000 (Oil and gas industry. Submarine pipeline systems. General requirements), establishes safety requirements for subsea marine pipeline systems by defining minimum requirements for design, materials, manufacturing, construction , testing, commissioning, operation, maintenance, re-inspection and disposal and is quite consistent with the ISO 13623 standard, which sets out the functional requirements for offshore pipelines (there are some differences).

GOST requires that parameters affecting the performance of the pipeline system be monitored and assessed. In this case, the frequency of monitoring or inspections should be such that the pipeline system is not endangered due to any deterioration or wear that may occur between two successive intervals (the frequency should ensure that the malfunction can be corrected in a timely manner). It is stated that if visual inspection or simple measurements are not practical or reliable, and available design methods and accumulated experience are not sufficient to reliably predict system performance, instrumentation of the piping system may be necessary.

GOST requirements for operation, inspection, modification and repair of pipelines apply to the following elements:

Instructions;

Storage of operational documentation;

Measurements of technical and operational parameters:

Basic principles of control and monitoring;

Special checks;

Pipeline configuration survey;

Periodic examinations;

Control and monitoring of external corrosion;

Pipelines and risers in the immersion zone;

Control and monitoring of internal corrosion;

Corrosion control;

Corrosion monitoring;

Defects and repairs.

However, these requirements are of a general nature and for practical use they need detailing, which is advisable to implement within the framework of the new standard (hereinafter referred to as the Standard).

It should be noted that selective application of international requirements is not always possible due to the heterogeneity of approaches in Russia and abroad to the regulation of safety at the same facilities.

General approach to the formation of the Standard

Currently, in the Russian Federation, technical regulation, including in the field of operation of main gas pipelines, is carried out in accordance with the Federal Law of December 27, 2002 No. 184-FZ “On Technical Regulation”, which fundamentally changed the domestic standardization system. The novelty of this system is as follows:

A 3-level system for constructing regulatory documentation is being created, in which only the requirements of the upper (directive) level, which are established by special technical regulations (STR) of the Russian Federation, are mandatory;

State (national) standards are voluntary;

Corporate standards are valid only among organizations that approve them;

The use of international standards as a basis for the development of national standards is permitted;

Responsibility for the safe operation of man-made facilities, including pipeline transport facilities, rests with their owners (customers).

Solving the problems of ensuring the safety of MT operation must take into account the requirements of domestic and foreign standards and link safety with eliminating the threat of harm to personnel, property and/or the environment, and risk with the amount of damage caused. This approach should focus on balancing operational and process risk management activities to find a sustainable balance between safety, functionality and cost. To do this, the basic provisions/principles of MT operation must be established, in terms of control, maintenance and repair of their elements, including inspections, inspections and surveys.

The standard must implement the provisions of the general concept of technical regulation in relation to the object of its regulation and relate to the fundamental documents (organizational, methodological and general technical standard).

The standard should be developed on the basis of sound scientific and technical provisions aimed at reducing risk and ensuring safety during the operation of transport equipment and ensure a modern level of organization and conduct of relevant work.

The standard must ensure the level of operational safety of the MT, which should be perceived as a combination of industrial safety, environmental safety, protection from unauthorized intervention and terrorist threats, labor protection, etc., no lower than onshore sites.

The standard should apply to the processes of operation, inspection, maintenance and repair of MTs laid on the continental shelf and in the inland seas of the Russian Federation.

The standard should establish (to a minimum extent) general provisions, basic guidelines, recommendations and mandatory general technical requirements, the most important norms and rules for processes, procedures, works and operations related to the operation, inspection, maintenance and repair of MT. The requirements of the Standard should not prevent initiatives to introduce modern methods and technical means, optimize technologies and organizational processes, and carry out work on the operation of MT on the basis of good maritime practice.

The standard must contain both safety requirements that take into account the hazardous factors characteristic of the operation of MT, and administrative provisions, which include rules for planning, organization, preparation, conduct, control, acceptance of various works and rules for confirming the conformity of equipment used for operation, inspection and repair , meeting the requirements. Main threats to MT security

An analysis of the available information on the experience of operating offshore pipeline systems for transporting hydrocarbons shows that the components of the general security threat are:

Natural and climatic factors;

Processes and phenomena in the geological environment;

Structural and technological defects of the pipeline;

Emergency technological situations;

Man-made hazards (explosive objects; sunken chemical weapons and sunken objects);

Activities at sea;

Actions of third parties.

According to available data, external threats (from the outside of the pipeline) prevail over internal ones (inside the pipe), both in terms of the overall accident rate and the degree of their danger. In this regard, priority was given to the questions of surveys of the IHL to ensure the diagnosis of its technical condition.

The standard should encourage the manifestation of personnel initiatives to introduce modern methods and technical means of operation, inspection and repair of MT, as well as to optimize relevant technologies and organizational processes based on good maritime practice.

The standard should provide:

Protection of human life and health, property, as well as prevention of actions that mislead consumers (users) regarding the purpose and safety of MT;

Concentration in a single document of the basic requirements of legal and regulatory documents in force in the field of operation, inspection, maintenance and repair of transport equipment;

Eliminating gaps in the regulation of activities related to operation, inspection, maintenance and repair of transport vehicles.

Particular attention should be paid to the requirements for inspection and repair of equipment related to special processes, procedures, work, marine operations, vessels and equipment.

The standard should be developed on the basis of sound scientific and technical provisions aimed at reducing risk and ensuring safety during the operation of MT and should ensure a modern level of organization and conduct of relevant work.

All main provisions, norms, requirements and rules of the Standard must be harmonized with their analogues of the existing Russian and foreign regulatory framework.

Requirements for offshore work (inspections and repairs of MT, offshore operations) should be based on the use of practical experience in the development and implementation of “offshore projects” in our country, as well as taking into account the applicable norms, rules and requirements of RMRS, Norwegian (DNV) and American (API ) standards, Canadian Standards Association guidelines, and other sources of information.

When developing the specified technical conditions and specifications, it is required to use scientific and technical documentation, including generally recognized international standards, such as API 1111 (1993), DNV (1996) and BS 8010 (1993), as well as the results of scientific research on this issue.

The standard should be developed on the basis of an integrated approach to organizing and carrying out all work on the operation of transport equipment, including repairs. At the same time, it is important to ensure the ability to maintain constant feedback to adjust and supplement requirements.

The standard should establish the following basic principles for the operation of MT:

1. The operation of MT should be aimed at preventing failures and reducing the severity of their consequences.
2. There are no uniform (universal) rules for the operation of MT. Individual rules must be established for each MT, taking into account the specifics of its use, maintenance and repairs. The initially established rules should be periodically analyzed and, if necessary, revised, taking into account the accumulated experience in operating the MT. Effective development of rules can and should be ensured by personnel directly servicing MT.
3. A significant part of probable MT failures is not related to the age of the gas pipeline and its operating means, but depends on the quality of construction, use and maintenance.
4. The operation of the MT should be based on a system of special measures to ensure a given level of reliability of the gas pipeline based on a unified system of expert diagnostic services, providing for maintenance and repair of its linear part according to the actual condition based on diagnostics and monitoring of the technical condition of the gas pipeline and its soil foundation.
5. Fundamental decisions on the maintenance and repair of motor vehicles must be justified by assessing the risk of unfavorable development of initial events (the reasons for these decisions).
6. Repair planning must be accompanied by identifying conditions that precede failures and predicting when failures will occur.
7. Major repairs should, if possible, be excluded through effective control and monitoring of the process of using MT, conducting timely inspections, diagnostics and forecasting changes in the technical condition of MT, repair and maintenance and repair work on problem sections of the gas pipeline.
8. Maintenance personnel should be focused on the need to generate informed proposals aimed at ensuring the reliability and safety of MT operation, as well as reducing operational risks.
9. Considering that each specific MT has specific local conditions, design and construction solutions, instructions from manufacturers and suppliers of equipment and materials used as part of the MT, detailed requirements for the operation, inspection and repair of MT should be developed and recorded in job and production instructions, drawings, diagrams and other documents.

The standard should be developed on the basis of the current scientific and technical documentation in the Russian Federation, taking into account design decisions for commissioned MTs, current domestic and international experience in the inspection, operation and repair of offshore pipelines and other underwater stationary facilities, as well as using departmental regulatory documents, technical literature, R&D results.

To minimize the volume of regulatory requirements in the Standard, it is advisable to use a mechanism of references to well-known specifications, practical recommendations and standards.

It seems that the regulation of activities for the operation of MT should be established by a special state standard, for the development of which it is necessary to involve specialists with comprehensive experience and knowledge both in the field of design and operation of offshore underwater pipelines, and the methods and technical means used in this case. It is especially important to take into account the experience of marine diving and underwater technical work on the inspection and repair of various underwater stationary objects.

Table - Regulatory documents in the field of design, construction and operation of offshore pipelines in force in the Russian Federation

International documents

UNECE document "Guidelines and good practices for ensuring the operational reliability of pipelines";

ISO 13623-2009 "Petroleum and gas industries - Pipeline transportation systems";

ISO 5623 Petroleum and gas industries. Pipeline transportation systems (ISO 5623 Petroleum and natural gas industries - Pipeline transportation systems).

ISO 5623 Petroleum and gas industries. Pipeline transportation systems (ISO 5623 Petroleum and natural gas industries - Pipeline transportation systems)

ISO 21809 External coatings for buried or subsea pipelines used in pipeline transport systems;

ISO 12944-6 "Anti-corrosion protection of steel structures using protective paint systems"

GOST R 54382-2011 Oil and gas industry. Subsea pipeline systems. General technical requirements. (DNV-OS-F101-2000. Oil and gas industry. Submarine pipeline systems. General requirements).

ASME B31.4-2006 Pipeline systems for the transport of liquid hydrocarbons and other liquids;

ASME B31.8-2003, Gas Piping Systems and Gas Distribution;

CAN-Z183-M86 "Oil and gas pipeline systems".

Departmental documents

VN 39-1.9-005-98 Standards for the design and construction of an offshore gas pipeline

The concept of technical regulation at OAO Gazprom (approved by order of OAO Gazprom dated September 17, 2009 No. 302)

STO GAZPROM 2-3.7-050-2006 (DNV-OS-F101) Marine standard. Underwater pipeline systems (approved by order of OJSC Gazprom dated January 30, 2006)

STO Gazprom 2-3.5-454-2010. Organization standard. Rules for the operation of main gas pipelines (approved and put into effect by Order No. 50 of OJSC Gazprom dated May 24, 2010),

"Regulations on independent technical supervision and quality control of the construction of facilities of the Yamal-Europe gas transmission system"