How an offshore oil platform works. Features of offshore oil and gas production

An oil platform is a huge industrial complex designed for drilling wells and extracting hydrocarbons located at great depths. Installations for the extraction of oil and gas from the bowels of the Earth are amazing: imagine a man-made structure weighing half a million tons, capable of drilling wells up to 10-13 km even in conditions of partial submersion under water - and you will understand that this is a triumph of engineering modern man. But even among these mighty structures there are giants, the mere sight of which causes awe:

TROLL-A

The TROLL-A reinforced concrete fishing platform is the world's heaviest artificial object capable of moving on the surface of our planet. The total weight of the natural gas platform is 1.2 million tons loaded with ballast (dry weight - about 650-680,000 tons) and a height of 472 meters (of which 369 is occupied by an underwater concrete structure). This is a real miracle of engineering, installed in the Norwegian gas and oil field Troll in the North Sea.

Drilling rigs "Uralmash"

The largest land drilling rigs have been produced in our country since the 70s. The Uralmash-15000 drilling rig was involved in drilling the Kola super-deep well: a 20-story building high structure was able to drill a well up to 15 km deep! But the largest installations on floating platforms are the Aker H-6e systems (pictured), also produced by Norwegians. The working deck area of ​​this design is 6300 m 2 , and the drilling depth reaches 10 km.

Statfjord-B

You can't miss the Statfjord-B drilling rig, the largest floating technical structure in the world. The height of the tower, built in Norway in 1981, with a concrete base is 271 meters, and total weight structures - 840,000 tons. industrial complex can produce up to 180,000 barrels of oil per day, while the tanks will be enough for 2,000,000 barrels. Moreover, the platform is a real city on the water: in addition to the drilling rig, it houses a seven-story high-class hotel, a chemical laboratory, a helipad and a whole fleet of rescue and support equipment.

Perdido Spar

But the deepest platform is located in the Gulf of Mexico, where it is moored at a depth of 2450 meters above the Perdido oil and gas field. The maximum capacity of the platform is 100,000 barrels of crude oil per day! The height of Perdido Spar is 267 meters, that is, this is a real underwater Eiffel Tower!

Eva-4000

Another giant, but of a new generation, is the Eva-4000 drilling platform, also located in the Gulf of Mexico, 240 km from Louisiana. It is owned by Noble Amos Runner and at a height of 106 meters (the platform does not provide for a residential complex) is capable of drilling at a depth of 9700 m.

The development of offshore oil and gas fields required the creation of unique structures - stationary offshore platforms. Fixing on one point in the middle of the open sea is a very difficult task. And over the past decades, the most interesting solutions have been developed, without exaggeration, examples of engineering genius.

The history of the oilmen going to sea began in Baku, on the Caspian Sea, and near Santa Barbara, California, on the Pacific Ocean. Both Russian and American oilmen tried to build a kind of piers that went several hundred meters into the sea in order to start drilling on the already discovered fields on land. But the real breakthrough occurred in the late 1940s, when, again, near Baku and now in the Gulf of Mexico, work began on the high seas. Americans are proud of the achievement of Kerr-McGee, which in 1947 drilled the first industrial well "out of sight of land", that is, at a distance of about 17 km from the coast. The depth of the sea was small - only 6 meters.

However, the famous Guinness Book of Records considers the famous "Oil Rocks" (Neft Daslari - Azerbaijani) near Baku to be the world's first oil platform. Now it is a grandiose complex of platforms that has continued to function since 1949. It consists of 200 separate platforms and bases and is a real city on the high seas.

In the 1950s, the construction of offshore platforms was underway, the bases of which were lattice towers welded from metal pipes or profiles. Such structures were literally nailed to the seabed with special piles, which ensured their stability during waves. The structures themselves were sufficiently "transparent" for passing waves. The shape of such a base resembles a truncated pyramid; in the bottom part, the diameter of such a structure can be twice as wide as in the upper part, on which the drilling platform itself is installed.

There are many designs of such platforms. Own developments, created on the basis of the operating experience of the "Oil Rocks", were in the USSR. For example, in 1976, the platform "Named April 28" was installed at a depth of 84 meters. But still, the most famous platform of this type is Cognac in the Gulf of Mexico, installed for Shell in 1977 at a depth of 312 meters. For a long time it was a world record. The development of such platforms for depths of 300-400 meters is still underway, however, such structures cannot resist ice attacks, and special ice-resistant structures were created to solve this problem.

In 1967, the largest American field, Prudhoe Bay, was discovered on the Arctic shelf of Alaska. It was necessary to develop stationary platforms that would withstand the ice load. Already at the early stages, two basic ideas appeared - the creation of large caisson platforms, and in fact, original artificial islands that would withstand a pile of ice, or platforms on relatively thin legs that would let the ice through, cutting its fields with these legs. Such an example is the Dolly Varden platform, nailed to the seabed through its four steel legs, each of which is a little more than 5 meters in diameter, while the distance between the centers of the supports is almost 25 meters. The piles that secure the platform go into the ground to a depth of about 50 meters.

Examples of an ice-resistant caisson platform are the Prirazlomnaya platform in the Pechersk Sea and Molikpaq, also known as Piltun-Astokhskaya-A, offshore Sakhalin Island. The Molikpaq was designed and built to operate in the Beaufort Sea, and in 1998 it was refurbished and started operating at a new location. The Molikpaq is a sand-filled caisson that acts as ballast to press the bottom of the platform against the seabed. In fact, the bottom of the Molikpak is a huge suction cup, consisting of several sections. This technology was successfully developed by Norwegian engineers in the process of developing deep water deposits in the North Sea.

The North Sea epic began back in the early 70s, but at first the oilmen did without exotic solutions - they built proven platforms from tubular trusses. New solutions were required when moving to great depths. The apotheosis of the construction of concrete platforms was the Troll A tower, installed at a depth of 303 meters. The base of the platform is a complex of reinforced concrete caissons that stick to the seabed. Four legs grow from the base, which support the platform itself. The total height of this structure is 472 meters, and this is the tallest structure that has ever been moved in a horizontal plane. The secret here is that such a platform moves without barges - it only needs to be towed.

A certain analogue of the "Troll" is the ice-resistant platform "Lunskaya-2", installed in 2006 on the Sakhalin shelf. Despite the fact that the depth of the sea there is only about 50 meters, it, unlike the Troll, must resist ice loads. The platform was developed and built by Norwegian, Russian and Finnish specialists. Its "sister" is the Berkut platform of the same type, which is installed at the Piltun-Astokhskoye field. Its technology complex, built by Samsung, is the largest facility of its kind in the world.

The 80s and 90s of the 20th century were marked by the emergence of new constructive ideas for the development of deep-water oil fields. At the same time, formally, the oil workers, crossing the 200-meter depth, went beyond the shelf and began to descend deeper along the continental slope. Cyclopean structures that were supposed to stand on seabed approaching the limit of what is possible. And a new solution was proposed again at Kerr-McGee - to build a floating platform in the form of a navigation milestone.

The idea is ingeniously simple. A cylinder of large diameter is being built, sealed and very long. At the bottom of the cylinder is placed a load of a material that has a specific gravity greater than that of water, such as sand. The result is a float with a center of gravity far below the water level. For its lower part, a Spar-type platform is attached with cables to bottom anchors - special anchors that are screwed into the seabed. The first platform of this type, called Neptune, was built in the Gulf of Mexico in 1996 at a depth of 590 meters. The length of the structure is more than 230 meters with a diameter of 22 meters. To date, the deepest offshore platform of this type is the Perdido rig operated by Shell in the Gulf of Mexico at a depth of 2,450 meters.

The development of offshore fields requires more and more new developments and technologies, not only in the actual construction of platforms, but also in terms of the infrastructure serving them, such as pipelines, for example, which must have special properties for working in offshore conditions. This process is going on in all developed countries that are engaged in the production of relevant products. In Russia, for example, the Ural pipe manufacturers from ChTPZ are actively developing the production of pipe products, specially oriented for operation on the shelf and in the difficult conditions of the Arctic. In early March, new developments were presented, such as large-diameter pipes for risers (risers connecting the platform to subsea equipment) and other structures that require resistance in the Arctic. The work is accelerated by the need for import substitution - from Russian companies there are more and more requests for casing pipes and other equipment for arranging wells under water. Technologies do not stand still, which means that there are opportunities for the development of new promising fields.

DRILLING PLATFORM, a hydraulic structure for drilling wells in the development of offshore oil and gas fields. Depending on the design and purpose, fixed offshore platforms (for production drilling) and floating drilling rigs (for exploration drilling) are distinguished.

Offshore fixed platforms, mostly three-tiered, are used at depths up to 350 m for simultaneous drilling, production and preparation of reservoir products for transportation. Platforms intended solely for the drilling of oil or gas wells, are made in a single-tier version. From the deck of a drilling platform, located at a height unattainable for waves, one or two drilling rigs can carry out the construction of several dozen vertical, directional, horizontal and branched (multilateral) wells. Stationary drilling platforms are fixed on the seabed in the following ways: piled (driving into the seabed of piles rigidly fastened to the drilling platform support block); gravity (they are held at the bottom due to the mass of the structure, while the support block is filled with soil or water for reliable subsidence to the seabed); combined, or pile-gravity (a flooded support array, located at the bottom, is additionally fixed with piles around the entire perimeter); using anchor chains or tension cables (if the drilling platform support block is made of pontoons fully or partially submerged in water). The supporting block of the drilling platform is made of steel (mainly tubular), reinforced concrete or combined (reinforced concrete gravity lower part, upper - steel lattice structure). The surface part of the drilling platform includes the main complexes: drilling, operational, energy, residential and life support. In the waters of the Arctic seas, ice-resistant drilling platforms with supports in the form of a cylinder, prism or cone are used to reduce the ice load.

Floating drilling rigs are subdivided into submersible (PBU), jack-up (SPBU), semi-submersible (FPBU) and drilling ships (BS).

MODUs are designed for drilling wells in shallow water in the depth range from 2 to 20 m (some up to 50 m). All MODUs have an underwater hull (flooded pontoon) on which support columns rest. To lift the MODU from the bottom, a system of soil erosion under the bottom is used to reduce suction forces.

The jack-up rig is used for exploratory drilling at depths from 5 to 150 m. The hull has rooms for various purposes - for equipment, storage, residential cabins. When transporting the jack-up rig, the supporting columns are maximally extended upwards. At the drilling point, the columns are lowered to the ground, the body is lifted out of the water with the help of a hydraulic or electromechanical lift, and the lower part of the columns, equipped with special shoes, is pressed into the ground.

MODU and BS are used at sea depths of 150-1500 m. The stability of MODU is ensured by the shape of the pontoon hull, the distance between the pontoons, as well as the number and diameter of the support columns on which the surface part is installed. MODU and BS are fixed at the drilling point using anchor systems or by providing dynamic positioning, carried out by special propulsion units built into the body of a submerged pontoon. BS, unlike other types of floating drilling rigs, retain the high seaworthiness characteristic of conventional ships.

Lit .: Vyakhirev R. I., Nikitin B. A., Mirzoev D. I. Arrangement and development of marine oil and gas fields. M., 2001.

Off the coast of Norway at the bottom north sea one of the richest oil and gas fields. Nature was challenged by man to build such a structure on the high seas that could withstand fierce storms and provide stability to a platform that serves to extract rich fuel reserves from the seabed.

Today we will talk about the Troll gas production platform. It is the highest concrete offshore platform in the world. Access to the platform is possible only by helicopter, wearing a rescue suit. The Troll gas field is located 60 kilometers off the coast of Norway. Natural gas reserves were formed here 130 million years ago. These huge gas reserves required the construction of some permanent structure that would be strong enough to produce gas from it for more than 50 years.

It is the tallest building ever to move relative to the surface of the Earth and is one of the tallest and most complex engineering projects in history. A story about a platform being towed into the North Sea in 1996 became a television sensation.

The Troll platform was towed over 200 km from Chany, in the northern part of Rogaland, to the Troll area, 80 km northwest of Bergen. The towing took seven days.
Produced gas is carried through the pipelines of the platform at speeds up to 2,000 miles per hour (890 m/s). This speed is provided by two gas compressors in order to increase production volumes.

In 1996, the platform set a World Record (Guinness Book of Records) as the ‘largest offshore gas platform’.

In 2006, the company that owns the platform held a concert for the workers. Singer Katie Meluoy was invited to host the "Deepest Concert Ever". The depth was 303 meters below sea level.

Four cyclopean concrete pillars protrude from the sea. The drilling deck and the entire superstructure of the platform rests on four massive concrete pillars that go down to the seabed to a depth of 300 meters. The base of the platform is made of 19 prefabricated concrete blocks made on land. The base was towed on ropes and sunk in a deep fjord, where four high supports were attached to them. The total height of each support is 369 meters, exceeding the height of the Eiffel Tower. By the way, in each of them has an elevator, which takes 9 minutes to go up. The walls of the cylindrical legs are over 1 meter thick.

Then the entire structure was loaded into the fjord to an even greater depth, and a platform was placed over the structure using barges. Then ballast water was pumped out of the structure and allowed to float a few centimeters and dock with the platform. Then the entire new completed structure was raised to the surface and prepared for a journey to the Troll field. The platform was towed to the open sea, and it became the largest structure ever moved from place to place in the history of mankind.

Being on the helipad, at an altitude of 76 meters above sea level, it is easy to forget that most of structure is under water. It's a bit like an iceberg. The height of the helipad exactly matches the height of the famous Empire State Building skyscraper.

Such an offshore platform is a real chemical plant, and since this industrial enterprise, here you can not do without a set of protective clothing. At the bottom is a gas production plant, and a little further is a gas processing plant, in the middle is a drilling rig. On this new platform, all production wells have not yet been discovered, in the end there will be 39 of them. Having covered the distance to the seabed, the drills plunge into it to a depth of one and a half kilometers. The wells are located within a radius of half a kilometer around the platform.

Drill stems weigh like clothes in a wardrobe and are always ready to use. On average, it takes a month to drill each well. However, in the first place, we are not interested in this, but what makes the whole structure stable.

The journey to the bottom of the sea can be made on an elevator that runs inside one of the giant pillars. When you are surrounded by the sea on all sides, there is a feeling that you are on another planet. On land, we also see tall buildings, giant tunnels and other cyclopean structures, but surrounded by the sea, the scale of this achievement of engineering is perceived as truly extraordinary. There is a feeling that there is no place on any planet where a person could not penetrate.

The pressure of the sea water column behind the wall is 30 times greater than the pressure inside the structure at the seabed and it would seem that it should crush the support. The reason why this does not happen is due to the combination of the strength of heavy reinforced concrete and the cylindrical shape of the support. This shape is best suited to resist this kind of pressure. That is why the hull of the submarine and the fuselage of the aircraft have the same shape.

At the very base of the platform, pipelines bend around a corner and, passing along the seabed, deliver gas to Norway 60 kilometers from this place. And below is a concrete floor, and under it is sea silt, the platform goes deep into the seabed. It looks like overturned coffee cups, nineteen in all, each deeply pressed into the sea mud. Imagine an overturned mug, pressed into the dirt, when you try to remove it from there, the suction force will firmly hold the cup in place. this is the principle of fixing the base of the structure.

Down at the seabed, the main task is to cope with the pressure of the water column, and up close to the top, with the wind and waves that crash on the platform. During a storm, waves can reach the deck located at a height of 30 meters above the sea. But this deck is large enough not to be flooded by the waves, and is securely attached to four pillars. They, in turn, are strong enough to withstand the impact of 5 million waves every year.

It is structures such as the giant Troll platform and the progress of engineering behind all this that give confidence that we can live and work anywhere in the sea, under any conditions. It is now not so much about how a person can hide from the sea, but how to coexist with him on the coast and in open waters.

We are making this publication for those who have always been interested in how an offshore drilling platform works and how this miracle of engineering works.

Types of offshore platforms:

• stationary oil Platform;


• offshore oil platform, freely fixed to the bottom;
• semi-submersible oil drilling platform;
  
  
  


• mobile offshore platform with retractable legs;
  
  
  


• drilling ship;
  
  
  


• floating oil storage (FSO) - a floating oil storage facility capable of storing oil or storing and shipping offshore;
  
  
  


• floating oil production, storage and offloading unit (FPSO) - a floating structure capable of storing, offloading and producing oil;
  
  
  


• oil platform with stretched supports (floating base with tension vertical anchorage).

The four main components of an oil platform: hull, drilling deck, anchor system and drilling rig allow solving the problems of exploration and production of black gold in high water conditions.

The hull is essentially a pontoon with a triangular or quadrangular base supported by huge columns. Above the hull is a drilling deck that can support hundreds of tons of drill pipes, several cranes and a full-sized helipad. A drilling rig rises above the drilling deck, the task of which is to lower / raise the drill to the seabed. At sea, the entire structure is held in place by an anchor system. Several winches pull tightly on steel mooring lines anchored to the ocean floor, holding the platform in place.

Principle of operation

The process of oil production begins with seismic exploration. At sea, seismic exploration is carried out with the help of special ships, usually with a displacement of up to 3,000 tons. Such vessels unwind seismic streamers behind them, on which hydrophones (receiving devices) are located and create acoustic waves using an oscillation source (air guns). Shock acoustic waves are reflected from the layers of the earth, and, returning to the surface, are captured by hydrophones. Thanks to such data, two-dimensional and three-dimensional seismic maps are created, which show potential reservoirs with hydrocarbons. However, no one can guarantee that he has found oil until it gushes from the well.

So, after exploration, the drilling process begins. For drilling, the team assembles the drill in sections. Each section is 28 meters high and consists of iron pipes. For example, the EVA-4000 oil platform is able to connect a maximum of 300 sections, which allows you to go deep into the earth's crust for 9.5 km. Sixty sections an hour, the drill is lowered at that rate. After drilling, the drill is removed to seal the well so that oil does not leak into the sea. To do this, blowout control equipment or a preventer is lowered to the bottom, thanks to which not a single substance will leave the well. The preventer with a height of 15 m and a weight of 27 tons is equipped with control equipment. It acts like a huge sleeve and is able to block the oil flow in 15 seconds.

When oil is found, the oil platform can move to another location to search for oil, and a floating oil production, storage and offloading unit (FPSO) arrives in its place, which pumps oil from the Earth and sends it to refineries onshore.

An oil platform can be anchored for decades, regardless of any surprises of the sea. Its task is to extract oil and natural gas from the depths of the seabed, separating contaminants and sending oil and gas ashore.