Offshore production plant for producing, processing and refining feed gases

Abstract

The present invention relates to marine production facilities that can be used to create marine production complexes to extract, process and process hydrocarbon feedstocks to produce liquefied natural gas (LNG), wide fraction light hydrocarbons (WFLH) and stable gas condensate (SGC) on the GBS, representing a novel marine hydrocarbon structure GDCPSO (gravity drilling chemical production storage and offloading). The offshore industrial complex comprises a gravitational structure (GBS) on which an upper portion is provided, comprising a drilling facility comprising a drilling rig (10), a torch portion (11), processing equipment (as a module (12)) for feed gas processing and processing, and a living area (13). The GBS accommodates tanks (14, 15, 16) for storing various processed products. The GBS center part (1) is a rectangular prism and is provided with a top plate (3), and the machining equipment is installed on the top plate (3). The GBS projection (2) extends along the side of the central portion (1) and has a vertical outer wall. The GBS center part (1) and the GBS protruding part (2) share a bottom plate (4), and the height of the protruding part (2) is lower than that of the center part (1). The GBS center part (1) has longitudinal and transverse walls (6) forming a cabin, including a ballast tank (17) and a tank (14, 15, 16) containing each processed product. The GBS projection (2) has an inner wall which is perpendicular to its outer wall and forms a ballast tank (17). The drilling machine (10) is mounted on the short end of the GBS central part (1), the cabin (18) below which serves as a drilling well. The preferred design is characterized in that the central compartment of the GBS is formed by a short end wall on one side thereof, including at least one consumable compartment (19), at least one chemical compartment (20) and at least one waste compartment (21). The GBS center part (1) also has an intermediate horizontal plate (5) housing an LNG storage tank (14) and between the intermediate horizontal plate (5) and the bottom plate (4) there are provided longitudinal and transverse walls (6) forming an additional ballast tank (17). The offshore complex is suitable for operation in water areas with ice in the north pole.

Description

Technical Field

[0001] The present invention relates to an offshore production facility which can be used to establish an offshore production complex for extracting, treating and processing hydrocarbon feedstocks on a gravity-based structure (GBS) to produce liquefied natural gas (LNG), wide-fraction light hydrocarbons (WFLH) and stable gas condensate (SGC), representing a new type of offshore oil and gas structure - GDCPSO (Gravity Drilling Chemical Production Storage and Offloading). Background Art

[0002] FPSO (Floating Production Storage and Offloading) systems are one of the most widespread technical solutions for offshore hydrocarbon processing.

[0003] Specifically, FLNG (Floating Liquefied Natural Gas) systems are used in offshore LNG plants. In this case, the LNG plant is part of a floating unit that produces, processes and liquefies natural gas, as well as stores and unloads LNG. FLNG is used in the development of offshore natural gas fields and is installed directly on the gas field using anchoring and / or mooring.

[0004] This design has the following disadvantages.

[0005] FLNG is not suitable for use in waters with severe ice conditions because the reliable positioning required to connect the installation hull to the underwater extraction system cannot be ensured when the ice moves. Therefore, its use is limited to offshore oil field development in ice-free waters.

[0006] There is an integrated production complex for processing raw gas on a gravity-based structure (GBS) (RU2762588C1, publication date: December 21, 2021), intended for working in near-shore areas and consisting of a GBS capable of accommodating an upper module with processing equipment. The GBS is designed for use in waters with thick ice.

[0007] The complex has the following disadvantages.

[0008] 1. The complex needs to be connected to the oilfield hydrocarbon extraction and processing infrastructure.

[0009] 2. The complex allows hydrocarbon offloading only from the sea-facing side of the GBS.

[0010] 3. GBS has a large number of tanks with a large total volume, which are used only as ballast tanks. These tanks do not have any other functions.

[0011] The closest to the proposed offshore complex is the technical proposal (KR20170049075A, publication date: May 10, 2017), according to which the floating unit for natural gas extraction, processing, liquefaction and LNG storage and unloading includes drilling facilities and is a floating drilling LNG production, storage and unloading unit (FDLPSOU). The unit includes a floating foundation (container), a drilling rig placed thereon for oil and gas production, a flare section, processing equipment (including a gas processing (purification and dehydration) unit, a fractionation unit and a gas liquefaction unit), unloading equipment, a power plant, accommodation and control rooms, as well as liquefied natural gas (LNG), liquefied petroleum gas (LPG) and stabilized gas condensate (SGC) storage tanks placed in the hull and a mooring turret.

[0012] The FDLPSOU is used to develop offshore natural gas fields and is placed directly on the gas field using a dynamic positioning system and connected to the underwater natural gas extraction system via a turret.

[0013] This design has the following disadvantages.

[0014] 1. In the case of drilling a production well and producing hydrocarbons at the same time, when the production turret is connected, it is difficult for the FDLPSOU unit to ensure the positioning required for drilling.

[0015] 2. Since reliable positioning cannot be ensured, neither FDLPSOU nor FLNG can be used in waters with severe ice conditions. Summary of the invention

[0016] The technical problem to be solved by the present invention is as follows: In view of the increasing production of hydrocarbons in Arctic offshore oil fields, there is an urgent need to develop a new efficient production complex for extracting and processing hydrocarbons suitable for operation in Arctic icy waters.

[0017] The solution proposed for the above-mentioned problem is to establish an offshore production complex for raw gas extraction, treatment and processing ("GDCPSO", Gravity Drilling Chemical Production Storage and Offloading), including a lower structure with a top, the top including drilling facilities, a flare section, processing equipment for raw gas treatment and processing, and living quarters, the lower structure accommodating storage tanks for various processed products. According to the present invention, the lower structure is a gravity structure (GBS), which has a central part and a protruding part, the central part is a rectangular prism, the rectangular prism has a top plate accommodating the processing equipment, and the GBS protruding part extends along the side of the central part and has a vertical outer wall, the central part and the protruding part share a bottom plate, the height of the protruding part is lower than the central part, the GBS central part has longitudinal and transverse walls, the longitudinal and transverse walls form compartments, including ballast tanks and compartments accommodating storage tanks for various processed products, and the GBS protruding part has an inner wall, which is perpendicular to its outer wall and forms a ballast tank.

[0018] The preferred design of the drilling facility includes a drilling rig mounted on the short end of the central section of the GBS, with a cabin below the drilling rig acting as a borehole.

[0019] The design also has compartments in the central portion of the GBS formed by the short end walls on one side thereof, which include at least one consumable compartment, at least one chemical compartment and at least one waste compartment.

[0020] Furthermore, some of the compartments in the central portion of the GBS, including at least one compartment formed by a short end wall on one side thereof, may be auxiliary compartments.

[0021] Furthermore, the central part of the GBS has an intermediate horizontal plate which accommodates a tank for one of the processed products, which is liquefied natural gas, and longitudinal and transverse walls between the intermediate horizontal plate and the bottom plate, which form additional ballast tanks.

[0022] In addition, some of the compartments in the GBS center section also form storage tanks for other process products, which are stabilized condensate and natural gas liquids.

[0023] The purpose of GDCPSO is to produce, treat and process hydrocarbons to produce LNG, WFLH and SGC.

[0024] GDCPSO is used for offshore oilfield development and is installed directly at the oilfield at sea without anchoring, mooring or any other system. After being lowered onto the foundation base foundation 9, GDCPSO is fixed in place by filling the ballast system.

[0025] GDCPSO is used for drilling of production wells and treatment of formation fluids for further processing.

[0026] The technical effects achieved by this technical solution are as follows.

[0027] The GBS protrusion increases the buoyancy of the GDCPSO and reduces its sinking during transportation to the installation site.

[0028] The increased bottom width of the GBS improves the stability of the entire structure during transportation, allowing a taller and heavier top structure to be installed on the GBS. Seawater is used as ballast during the transportation phase.

[0029] The ballast tanks in the outer periphery within the protruding part of the GBS make the GBS easy to balance, that is, the GBS sinks evenly without trimming and rolling. Some tanks function as ballast tanks during transportation, and after the GBS is installed in the oil field, they are used as tanks for storing consumables, chemicals, waste, utility tanks and drilling wells during operation.

[0030] The GDCPSO can be secured in place by filling the ballast tanks with seawater and solid ballast.

[0031] The bulge can also protect the center of the GBS from drifting ice and emergency ship impact.

[0032] The salient can also serve as the basis for the unloading terminal of raw gas processing products (LNG, WFLH, SGC). BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The topside layout of the proposed offshore complex is shown.

[0034] Figure 2 – Figure 1 Cross section AA.

[0035] Figure 3 – Figure 1 Longitudinal section BB.

[0036] Figure 4 – Figure 1 Longitudinal section CC.

[0037] Figure 5 – Layout of the GBS main cabin.

[0038] Figure 6 – Figure 2 Vertical wall arrangement of GBS in the DD section.

[0039] Figure 7 – Figure 2 The GBS vertical wall arrangement in the EE section. DETAILED DESCRIPTION

[0040] The proposed GDCPSO offshore complex is a fully integrated technology product that combines processing, engineering and auxiliary equipment for drilling, raw gas extraction, handling, production, storage and offloading of LNG, WFLH and SGC.

[0041] The GDCPSO is manufactured in a dedicated shipyard and float-towed to the installation site.

[0042] GDCPSO is installed on the seabed of the oil field directly at the source of raw materials27( Figures 2 to 4 ) or installed at a distance from the oil field to carry out hydrocarbon extraction operations, depending on the oil field development plan, the water depth exceeds 14 meters. In order to prevent the GBS base foundation 9 and the seabed 27 around the GBS from being scoured, gabions or other similar structures or berms can be arranged to backfill and reinforce the seabed. After the oil field development is completed, the production complex can be unballasted and moved to another location for operation. Therefore, it can be used for hydrocarbon production in shallow and medium depth oil fields.

[0043] The development of GDCPSO will make it possible to develop oil fields located in shallow waters of the Arctic Ocean.

[0044] The main components of GDCPSO for hydrocarbon (raw gas) extraction, treatment and processing are GBS and top modular drilling and processing equipment ( Figures 1 to 4 ).

[0045] GBS is a three-dimensional reinforced concrete structure that serves as a supporting unit for drilling facilities and includes a drilling rig 10, a flare section 11, a top processing module 12, and a living quarters module 13. It is also used as a storage for various products of processed raw gas (i.e., LNG, WFLH, and SGC), consumables, chemicals, and waste, and is installed on the seabed 27 by virtue of its own weight.

[0046] The central part 1 of the GBS is a rectangular parallelepiped having a top plate 3. The protruding part 2 of the GBS extends along the side of the central part 1 to the periphery thereof. The central part 1 and the protruding part 2 of the GBS share a bottom plate 4, and the height of the protruding part 2 is lower than that of the central part 1.

[0047] The central part 1 of the GBS includes the main load-bearing structure - vertical walls 6 and horizontal plates (top plate 3, bottom plate 4 and middle plate 5). The load-bearing structure supports the spatial rigidity required by the GBS frame, for example when the GDCPSO remains afloat before transportation and installation. The vertical walls 6 made of reinforced concrete also divide the GBS into multiple compartments according to its intended use.

[0048] The GBS top plate 3 accommodates a reinforced concrete support 7 , on which a drilling rig 10 , a flare unit 11 , a processing module 12 , and a living area module 13 are mounted.

[0049] Since the vertical walls 6 also act as load bearing structures, transferring loads from the top to the floor slab 4 and the base foundation 9 , reinforced concrete supports 7 are erected above the intersections of the vertical walls 6 in the GBS core 1 .

[0050] The GBS roof 3 slopes from the centerline to the edge to drain atmospheric precipitation and process leaks. The roof 3 is designed to withstand explosions in emergency situations. To prevent cryogenic leaks, the roof 3 is reinforced with steel bars made of cold-resistant steel.

[0051] In order to distribute the load of the storage tank storing LNG, one of the raw gas processing products, the design includes a horizontal intermediate plate 5 between the top plate 3 and the bottom plate 4. The vertical wall 6 below the plate transfers the load to the bottom plate 4 and ensures the spatial rigidity of the structure.

[0052] Tension reinforced concrete based on modified normal density concrete is the main material of the central part 1 of the GBS.

[0053] The vertical walls 6 divide the GBS center 1 into multiple compartments ( Figures 5 to 7). Some (compartments 14, 15, 16) are used to store finished products; some (compartments 17 along the long sides of the GBS) are used to store water or solid ballast. The compartment 18 formed on one side by the short end walls of the center section 1 is used as a borehole well, at least one compartment 19 is used to store consumables, at least one compartment 20 is used to store chemicals, at least one compartment 21 is used to store waste, and at least one compartment 22 is used as an auxiliary compartment. The GBS center section 1 also accommodates an engineering compartment 23. During transportation and operation, compartments 19 to 23 are also used as ballast tanks. During operation, the consumables, chemicals and waste in the individual compartments 19, 20 and 21 are also considered as ballast.

[0054] The compartment 17 formed by the vertical walls 6 of the GBS nose 2 is contained in the ballast system.

[0055] The GDCPSO can remain afloat during transportation by sea to the installation site and can withstand ice shock under freezing conditions. In order to fix the floating GDCPSO on the base foundation 9 at the installation site, the ballast tank 17 is filled with seawater.

[0056] The external dimensions of the GDCPSO may vary depending on its production capabilities.

[0057] The main spatial planning solution for the GBS structure is defined by the technical parameters as well as the internal and external loads that affect the GBS structure, taking into account their maximum possible negative combination.

[0058] The main uses of GBS protrusion 2 are as follows:

[0059] - Achieve the desired target GBS buoyancy parameters;

[0060] - Accommodate the ballast tank 17, which is mainly used to balance the GBS and ensure that the GBS floats stably without shaking or tilting;

[0061] - Form a natural protective barrier in the event of a designed emergency collision / ship impact; the protrusion 2 will bear and absorb most of the collision energy, preventing damage to the main volume of the GBS frame, ensuring the integrity and preservation of the main tank and top load-bearing structure;

[0062] - Accommodate auxiliary processing and marine equipment to ensure berthing and unloading of tankers for LNG, WFLH and SGC.

[0063] LNG, WFLH and SGC storage tanks are installed in GBS compartments 14, 15 and 16.

[0064] GBS center 1 has multiple tanks ( Figure 5 ), these tanks may be of different designs depending on the nature of the substance to be stored.

[0065] Membrane tanks are used for liquefied LNG storage. In this case, the tank consists of a metal membrane made of stainless steel or Invar (Fe-Ni alloy) and is separated from the concrete structure by an insulation layer, and the tank is installed in a concrete cabin. The insulation layer is directly located on the top plate 3, the middle plate 5 and the GBS vertical wall 6, transferring the load of the tank and its liquid contents to the above-mentioned boundary structure. Therefore, the GBS plates and walls serve as a supporting structure for the membrane tank, which are integrated with the membrane tank into a single structural unit. To prevent any leakage, the bottom and sides of the membrane tank have a second barrier, namely an additional membrane installed in the insulation layer.

[0066] The WFLH and SGC tanks consist of GBS concrete compartments 15 and 16, whose boundary structures act as barriers.

[0067] Smaller storage compartments 19, 20 and 21 that serve as storage tanks for consumables, chemicals and waste (e.g., diesel, oil, mud, service water, glycol solutions, drill cuttings, drilling wastewater, deionized water, fresh water, etc.) are located along the short end of the GBS.

[0068] The auxiliary compartments 22 and engineering compartments 23 in the GBS center section 1 are located on both sides and in the middle of the main LNG, WFLH and SGC storage compartments 14, 15 and 16. These compartments are used to meet processing needs, equipment, service fluids, and personnel access and evacuation routes. The outer surfaces of the boundary walls of the compartments 14, 15 and 16 (LNG, WFLH and SGC tanks) can be inspected through dry compartments along the perimeter of the main hydrocarbon storage compartments.

[0069] Engineering equipment includes: power supply system, including substation; heating, ventilation and air conditioning (HVAC) system; ballast water heating and recirculation system; water supply and treatment system; fire pumps and pipes; foam fire extinguishing system slide rails; electrochemical corrosion protection system; telecommunications and alarm systems and video surveillance systems. Most of the engineering equipment is located in / on the top plate 3 and / or processing module 12, and the rest is located in the engineering compartment 23. The auxiliary compartment 22 can remain empty and be entered with the help of ladders and manholes.

[0070] The reinforced concrete bracket 7 of the upper module on the GBS top plate 3 ensures the transfer of supporting loads from the drilling rig 10, the flare section 11, the processing module 12 and the living quarters module 13 to the GBS main load-bearing structure. Structurally, the bracket 7 is a reinforced concrete tower with embedded heads.

[0071] The positions of the reinforced concrete supports 7 correspond to the intersection points of the GBS vertical walls 6, so as to distribute the loads from the top modules.

[0072] The reinforced concrete support 7 is designed to be high enough to provide sufficient space between the GBS top plate 3 and the bottom of the drilling rig 10, flare 11, processing module 12 and living area module 13, so as to install pipes and cables 24 between the top and the equipment in the GBS cabin, and to ensure that personnel and vehicles can pass through the GBS top plate 3.

[0073] The GBS ballast system includes inner ballast tanks 17 formed by vertical walls 6 (including the ballast tanks below the middle plate 5), and outer ballast tanks 17 in the GBS center section 1 and the GBS nose section 2, respectively. To prevent the water in the ballast tanks 17 from freezing, the design includes a ballast recirculation and heating system. The water in the ballast tanks 17 is heated using the waste heat of the flue gas of the gas turbine mounted on the top module.

[0074] The ballast system has two main functions:

[0075] - Ballasting, i.e. changing the weight of the GBS to ensure the required draft of the GBS when floating and the structural stability of the GBS after it is installed on the base foundation 9;

[0076] - GBS balancing, i.e. keeping the GBS stable and floating without roll and pitch, by compensating the deviation of the structure's centre of gravity from its geometric centre through ballast water.

[0077] The topside includes the processing equipment consisting of processing modules 12. The number of processing modules 12 is determined during the production complex engineering phase. The location of the modules on the GBS takes into account their weight, thus ensuring that the center of gravity of the GDCPSO is close to the geometric center of the GBS, thereby reducing the volume of ballast water required to balance the structure when floating.

[0078] The processing module 12 is a three-dimensional steel frame with supports for accommodating processing equipment, electrical equipment, automation systems, etc.

[0079] Fundamentally, the process module 12 is no different in design and layout from topside modules used in other types of offshore structures in the oil and gas industry.

[0080] The modules house feed gas purification and treatment processing units, gas liquefaction equipment, equipment for offloading LNG, WFLH and SGC to tankers, as well as auxiliary equipment and utilities.

[0081] The processing systems used to treat and utilize the raw materials produced from the well are designed to work with formation fluids and produced gas, WFLH and stabilized gas condensate. These systems are similar to those typically used in onshore oil fields. The difference is that the marine version of the equipment is used.

[0082] To facilitate equipment maintenance and personnel access, each processing module 12 has multiple levels (decks). The main level 8 of each processing module 12 is at the same height, so that evacuation routes and top load movement can be combined, thereby reducing the load on the GBS top plate 3. The height of the other levels of the processing module 12 depends on its function and equipment.

[0083] The LNG, WFLH and SGC unloading docks 25 are structurally integrated with the GBS and the top and are located on both long sides of the GBS. The docks 25 are equipped with mooring fenders, releasers and unloading platforms with loading and unloading arms and other vessels and processing equipment that can be unloaded. The figure shows the water level 26 in the water area.

[0084] The compartments may be separated by transverse bulkheads, except for the main LNG storage tank 14. Openings may be made in the walls of the ballast tank 17 to allow water to flow through, and personnel passages and cable and pipe penetrations may be made in the engineering compartments 22 and 23.

[0085] The drilling facilities are designed for the operating conditions of offshore oil fields and are designed for the corresponding climate. To ensure the smooth progress of drilling work, the drilling facilities include a drilling rig 10 ( Figure 1 , Figure 4 ), the drilling rig 10 has a handling device, blowout prevention equipment, a mud pump, a mud circulation system, a concrete pouring facility, a pneumatic conveying system, a mud preparation and injection system, a drilling wastewater collection system, a hydraulic drive device of the drilling rig 10 mechanism, a bulk material storage, etc.

[0086] The drilling rig 10 can ensure multi-well drilling and well repair of vertical wells, directional wells and horizontal wells throughout the year. Multi-well drilling is ensured by moving the drilling rig 10 in the entire well pattern.

[0087] The drilling rig 10 is mounted at the short end of the GBS center section 1, and the cabin 18 below it is used as a drilling well.

[0088] The drilling rig 10 comprises a base frame with a substructure equipped with equipment and systems to ensure drilling. The handling device of the drilling rig 10 allows it to be positioned above any point in the well pattern and to fix the drilling rig 10 in this position. The drilling is carried out by drilling a well 18 in the GBS ( Figure 4 to Figure 7 ).

[0089] The well fluids handling and disposal processing system is designed to operate as part of an integrated GDCPSO.

[0090] The design includes high and low pressure flare systems for the safe handling of gases from high and low pressure process equipment, including hydrocarbon gases / steam that are not used for power generation or heat. The flare system is also used during emergencies and / or blowdowns. Gases from the high and low pressure systems are sent to the flare section 11 and burned at the flare head ( Figure 1 , Figure 3 ).

[0091] The living area module 13 is used to provide accommodation ( Figure 1 , Figure 3 , Figure 4 ). The living quarters module 13 is a safe, fully functional, fireproof, secure and reliable building that meets all applicable architectural, design, sanitary and general technical requirements. The living quarters module 13 is developed as part of the superstructure together with other structures and systems.

[0092] The living area module 13 is a fully functional modular structure that includes living, public use, hygiene, medical and food facilities as well as auxiliary equipment facilities that support the functions of the living area module 13.

[0093] In order to meet safety requirements, the living quarters module 13 is installed as far away as possible from the most dangerous operating area where the drilling facility 10 is located.

Claims

1. An offshore production complex for raw gas extraction, treatment and processing, comprising a substructure having a top portion, the top portion including drilling facilities, a flare section, processing equipment for raw gas treatment and processing, and living quarters, the substructure accommodating storage tanks for various processed products, characterized in that: The lower structure is a gravity-based structure (GBS) having a center portion and a protrusion, the center portion being a rectangular prism having a top plate for accommodating the processing equipment, and the GBS protrusion extending along the side of the center portion and having a vertical outer wall, the center portion and the protrusion sharing a bottom plate, the height of the protrusion being lower than the center portion, the GBS center portion having longitudinal and transverse walls forming compartments including ballast tanks and compartments for accommodating storage tanks for respective processed products, and the GBS protrusion having an inner wall which is perpendicular to its outer wall and forms a ballast tank.

2. The complex according to claim 1, characterized in that The drilling facility includes a drilling rig mounted on the short end of the central portion of the GBS, and a cabin below the drilling rig is used to drill a well.

3. The complex according to claim 1, characterized in that: The compartments of the central part of the GBS formed by the short end wall on one side thereof include at least one consumable compartment, at least one chemical compartment and at least one waste compartment.

4. The complex according to claim 1, characterized in that: Some of the compartments in the central part of the GBS, including at least one compartment formed by a short end wall on one side thereof, are auxiliary compartments.

5. The complex according to claim 1, characterized in that The central part of the GBS also has an intermediate horizontal plate located thereon, which accommodates storage tanks for the corresponding processed product, which is liquefied natural gas, and longitudinal and transverse walls are arranged between the intermediate horizontal plate and the bottom plate, and the longitudinal and transverse walls form additional ballast tanks.

6. The complex according to claim 5, characterized in that Some of the compartments in the central part of the GBS form storage tanks for other corresponding process products, which are stable gas condensate and wide-cut light hydrocarbons.

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