Offshore production facility for producing, treating, and purifying raw gas

Abstract

The present invention relates to an offshore production facility, which can be used in the manufacture of an offshore production complex facility for producing liquefied natural gas (LNG), a wide range of light hydrocarbons (WFLH), and stable gas condensate (SGC) on a GBS by extracting, treating, and processing hydrocarbon raw materials. Thus, it represents a new type of offshore oil and gas structure, namely GDCPSO (Gravity Drilled Chemical Production Storage Offloading). The offshore industrial complex facility comprises a gravity-based structure (GBS) with an upper deck having a drilling facility with a drilling rig 10, a flare unit 11, processing equipment for treating and processing raw gas as a module 12, and a residential area 13. The GBS houses storage tanks 14, 15, 16 for corresponding processed production products. The central part 1 of the GBS is a rectangular column having an upper slab 3, on which the above-mentioned processing equipment is installed. The GBS protrusion 2 extends along all sides of the central part 1 and has a vertical outer wall. The central part 1 of the GBS and the GBS protrusion 2 share a base slab 4, and the height of the protrusion 2 is lower than that of the central part 1. The central part 1 of the GBS has vertical and transverse walls 6 that form compartments including a ballast compartment 17 and compartments for housing the storage tanks 14, 15, 16 for corresponding processed production products. The GBS protrusion 2 has an inner wall that is perpendicular to its outer wall and forms a ballast compartment 17. The drilling rig 10 is installed at the short end of the central part 1 of the GBS, and the compartment 18 below it functions as a borehole well. A preferred design is characterized in that the compartments of the central part of the GBS, including at least one consumable compartment 19, at least one chemical compartment 20, and at least one waste compartment 21, are formed by the short end wall on one side of the central part. The central part 1 of the GBS also has an intermediate horizontal slab 5 for housing the LNG storage tank 14, and between the intermediate horizontal slab 5 and the base slab 4, there are vertical and transverse walls 6 that form an additional ballast compartment 17. This offshore complex facility is suitable for operating in waters with ice field conditions in the Arctic.

Description

Technical Field

[0001] The present invention relates to an offshore production facility, and can be used in the manufacture of an offshore production complex for producing liquefied natural gas (LNG), a wide range of light hydrocarbons (WFLH), and stable gas condensate (SGC) by extracting, treating, and processing hydrocarbon raw materials on a gravity-based structure (GBS). Therefore, it represents a new type of offshore oil and gas structure, namely GDCPSO (Gravity Drilling Chemical Production Storage and Offloading).

Background Art

[0002] The FPSO (Floating Production Storage and Offloading) system is one of the most widespread technical solutions in offshore hydrocarbon processing.

[0003] In particular, the FLNG (Floating Liquefied Natural Gas) system is used in offshore LNG plants. In this case, the LNG plant is part of a floating facility for producing, treating, and liquefying natural gas, as well as storing and offloading LNG. FLNG is used in the development of offshore natural gas fields and is installed directly at the oil field using mooring and / or anchoring.

[0004] This design is characterized by the following drawbacks.

[0005] FLNG is not used in waters with severe ice conditions because it becomes impossible to ensure the reliable positioning required to connect the installation hull to the subsea extraction system when ice floes move. Therefore, the use of FLNG is limited to the development of offshore oil fields in ice-free seas.

[0006] There is an integrated production complex for processing raw gas on a GBS (Gravity-Based Structure) that houses upper deck modules equipped with processing equipment for operations in coastal areas (Russian Patent No. 2762588, Publication Date: December 21, 2021). This GBS design is suitable for use in waters with severe ice conditions.

[0007] This complex facility is characterized by the following drawbacks. 1. This complex facility requires connection to hydrocarbon extraction and processing infrastructure in the oil field. 2. This complex facility can only discharge hydrocarbons from the side facing the sea of the GBS. 3. The GBS has a number of compartments with a considerable total volume used only as ballast compartments. These compartments have no other functions.

[0008] The closest to the proposed offshore complex facility is a technical solution (Korean Patent Application Publication No. 20170049075, Publication Date: May 10, 2017). According to this technical solution, floating facilities for natural gas extraction, processing, liquefaction, and storage and discharge of LNG are equipped with drilling facilities and are floating drilling type LNG production storage and discharge units (FDLPSOU). This facility includes a floating foundation (ship), a drilling rig arranged on the floating foundation for oil and gas production, a flare unit, processing equipment equipped with gas treatment (purification and dehydration) facilities, fractionation facilities, and gas liquefaction facilities, a landing device, a power plant, accommodation facilities, a control room, and further tanks for liquefied natural gas (LNG), liquefied petroleum gas (LPG), and stabilized gas condensate (SGC) arranged inside the hull of the ship, and a mooring turret.

[0009] The FDLPSOU is used to develop offshore natural gas fields, is directly arranged in the oil field using an automatic ship position holding system, and is connected to a subsea gas extraction system with the assistance of a turret.

[0010] This design is characterized by the following drawbacks. 1. When simultaneously drilling production wells and producing hydrocarbons, it is difficult for the FDLPSOU unit to ensure the positioning required for drilling when the production turret is connected. 2. Since it is impossible to ensure reliable positioning for both the FDLPSOU and FLNG, they are not used in waters with severe ice field conditions.

Prior Art Documents

Patent Document

[0011]

Patent Document 1

Patent Document 2

Summary of the Invention

[0012] The technical problem to be solved by the present invention is as follows. Considering the increasing production of hydrocarbons from offshore oil fields in the Arctic region, it is necessary to urgently develop a new and efficient production complex for hydrocarbon extraction and processing suitable for operation in waters with ice field conditions in the Arctic region.

[0013] The solution proposed for the above problem is an offshore production complex for the extraction, treatment, and processing of raw gas (referred to as "GDCPSO", i.e., gravity drilling type chemical production storage and loading), having an infrastructure with an upper deck having a drilling facility, a flare unit, processing equipment for the treatment and processing of raw gas, and a residential area, and its foundation houses storage tanks for the corresponding processed products. According to the present invention, the infrastructure is a gravity structure (GBS) having a central part and a protruding part. The central part is a rectangular column having an upper slab for housing processing equipment, and the GBS protruding part extends along the entire perimeter along all sides of the central part and has a vertical outer wall. The central part and the protruding part share a base slab, and the height of the protruding part is lower than that of the central part. The GBS central part has vertical and horizontal walls forming compartments including a ballast compartment and a compartment for housing storage tanks for the corresponding processed products. The GBS protruding part has an inner wall that is perpendicular to its outer wall and forms a ballast compartment.

[0014] A preferred design of the drilling facility includes a drilling rig installed at the short end of the GBS central part, and the compartment below the drilling rig functions as a borehole well.

[0015] A preferred design is also characterized in that the compartments in the central part of the GBS, including at least one consumable compartment, at least one chemical compartment, and at least one waste compartment, are formed by the short end wall on one side of the central part.

[0016] Furthermore, a part of the compartments within the central part of the GBS includes at least one of the compartments formed by the short end wall on one side of the central part and can be used as auxiliary compartments.

[0017] Furthermore, the central part of the GBS also has an intermediate horizontal slab for accommodating a storage tank for one of the processed products which is liquefied natural gas, and there are vertical and horizontal walls between the intermediate horizontal slab and the base slab to form an additional ballast compartment.

[0018] Furthermore, a part of the compartments within the central part of the GBS forms storage tanks for other processed products which are stable gas condensate and natural gas liquids.

[0019] The purpose of the GDCPSO is to produce, process, and refine hydrocarbons to produce LNG, WFLH, and SGC.

[0020] The GDCPSO is used for the development of offshore oil fields and is directly installed on the offshore oil field without the need for any anchoring, mooring, or other systems. After being fixed on the base foundation 9 by filling the ballast system, the GDCPSO is fixed in place.

[0021] The GDCPSO is used for the drilling of production wells and the treatment of formation fluids for further processing.

[0022] The technical results achieved by the proposed technical solution are as follows.

[0023] The GBS protrusion increases the buoyancy of the GDCPSO and reduces its submergence during transportation to the installation location.

[0024] When the width at the lower part of the GBS increases, the overall structural stability during its transportation is enhanced, enabling the installation of a superstructure with a greater height and weight on the GBS. During the transportation stage, seawater is used as ballast.

[0025] The ballast compartments in the area around the GBS inside the protrusion facilitate the balancing of the GBS, that is, evenly submerging the GBS without trim and list. Some compartments that function as ballast tanks during transportation are used for storing consumables, chemicals, waste, public facilities, and as boreholes during operation after the GBS is installed in the oil field.

[0026] The ballast compartments may be filled with seawater and solid ballast, and the GDCPSO may be fixed in place.

[0027] The protrusion also protects the central part of the GBS from drifting ice and sudden ship impacts.

[0028] The protrusion also functions as the foundation for a jetty for loading the products (LNG, WFLH, and SGC) obtained by processing the raw material gas.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0030] The proposed GDCPSO offshore complex is a fully factory-prepared technical product that is a combination of processing, engineering, and auxiliary equipment for drilling, extraction of raw gas, treatment, production, storage, and loading of LNG, WFLH, and SGC.

[0031] The GDCPSO is fabricated at a dedicated base and towed offshore to the installation site.

[0032] The GDCPSO is installed on a dedicated foundation 9 on the seabed 27 (Figs. 2 - 4) either directly in the oil field where the raw materials are supplied according to the oil field development plan or at a location away from the oil field enabling hydrocarbon extraction operations. In this case, the water depth exceeds 14 m. To prevent scouring of the GBS foundation 9 and the seabed 27 around the GBS, gabions, or other similar structures, or berm backfilling may be placed for seabed reinforcement. When the development of the oil field is completed, the production complex can be deballasted and moved to operate at another location. Therefore, it can be used for producing hydrocarbons from shallow and medium-depth oil fields.

[0033] The development of the GDCPSO enables the development of oil fields located in the shallow waters of the Arctic Ocean.

[0034] The main components of the GDCPSO for the extraction, treatment, and processing of hydrocarbons (raw gas) are the GBS and the upper deck, i.e., modularized drilling and processing equipment (Figs. 1 - 4).

[0035] The GBS functions as a support unit for the drilling facility and is equipped with a drilling rig 10, a flare unit 11, an upper deck processing module 12, and a living quarter module 13. It also functions as a storage unit for each of the processed raw gas, i.e., LNG, WFLH, and SGC, consumables, chemicals, and waste products, and is a three-dimensional reinforced concrete structure designed to be installed on the seabed 27 with the assistance of its own weight.

[0036] The central part 1 of the GBS is a rectangular column with an upper slab 3. The GBS protrusion 2 extends along the side of the GBS central part 1 over its entire perimeter. The GBS central part 1 and the protrusion 2 share a base slab 4, and the height of the protrusion 2 is lower than that of the central part 1.

[0037] The GBS central part 1 is provided with a main load-bearing structure, namely a vertical wall 6 and horizontal slabs (upper slab 3, base slab 4, and intermediate slab 5). This load-bearing structure supports the required spatial rigidity of the GBS framework, for example, when the GDCPSO is transported and floating before installation. Also, the vertical wall 6 made of reinforced concrete divides the GBS into compartments according to the intended use.

[0038] The GBS upper slab 3 houses 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.

[0039] Since the vertical wall 6 also functions as a load-bearing structure for transmitting loads from the upper deck to the base slab 4 and the foundation pedestal 9, the reinforced concrete support 7 is built above the intersection of the vertical wall 6 within the GBS central part 1.

[0040] The GBS upper slab 3 slopes from the centerline towards the edge to discharge atmospheric sediments and processing effluents. The upper slab 3 is designed to withstand explosions in case of emergencies. For the purpose of protecting effluents at extremely low temperatures, the upper slab 3 is reinforced with steel bars made of highly cold-resistant steel.

[0041] To disperse the load from a tank storing LNG, one of the products obtained by processing raw gas, this design is provided with a horizontal intermediate slab 5 between the upper slab 3 and the base slab 4. The vertical wall 6 under this slab transmits the load to the base slab 4 and ensures the spatial rigidity of the structure.

[0042] Reinforced concrete based on improved normal density concrete with tension reinforcement is the main material of the GBS central part 1.

[0043] The vertical wall 6 divides the GBS central part 1 into compartments (Figs. 5 to 7). Some compartments (compartments 14, 15, 16) are used for storing the final product, and others (compartment 17 along the long side of the GBS) are used for water or solid ballast. The compartment 18 formed by the short end wall on one side of the central part 1 is used as a borehole well, at least one compartment 19 is used for storing consumables, at least one compartment 20 is used for storing chemicals, at least one compartment 21 is used for storing waste, and furthermore, at least one compartment 22 is used as an auxiliary compartment. The GBS central part 1 also houses the engineering compartment 23. During transportation and operation, compartments 19 to 23 are also used as ballast compartments. During operation, the consumables, chemicals, and waste in compartments 19, 20, and 21 respectively are also regarded as ballast.

[0044] The compartment 17 formed by the vertical wall 6 of the GBS protrusion 2 is included in the ballast system.

[0045] The GDCPSO can remain floating during sea transportation to the installation site and can withstand the impact of the ice field under ice field conditions. To fix the floating GDCPSO at a fixed position on the foundation 9 at the installation site, the ballast compartment 17 is filled with seawater.

[0046] The outer dimensions of the GDCPSO can vary according to its production capacity.

[0047] The main spatial planning solution of the GBS structure is determined by the technical parameters and the internal and external loads affecting the GBS structure, and the maximum possible negative combinations thereof are considered.

[0048] The protrusion 2 of the GBS serves the following main purposes: Achieving the required target GBS buoyancy parameters, Accommodate a ballast section 17 mainly for the purpose of GBS balancing to ensure that the GBS floats in a stable state without roll or trim. When a sudden collision / ship impact occurs in the design such that the protrusion 2 withstands and absorbs most of the collision energy to form a natural protective wall, prevent damage to the main volume of the GBS framework, and ensure the integrity and preservation of the main tank on the upper deck and the load-bearing structure. Accommodate auxiliary processing and shipboard equipment to ensure that the tanker moors and discharges LNG, WFLH, and SGC.

[0049] The storage tanks for LNG, WFLH, and SGC are installed in GBS sections 14, 15, and 16.

[0050] The GBS central part 1 has several tanks (Figure 5) that may have different designs according to the characteristics of the substances to be stored.

[0051] Membrane tanks are used for the storage of LNG. In this case, tanks made of stainless steel or Invar (Fe-Ni alloy) metal membranes separated from the concrete structure by a heat-insulating layer are installed within the concrete section. The insulating layer is directly located on the upper slab 3, the intermediate slab 5, and the GBS vertical wall 6, and transmits the load from the tank and its liquid contents to the above-mentioned boundary structure. Thus, the GBS slab and wall function as a support structure for the membrane tank and are integrated into a single structural unit together with the membrane tank. To prevent any leakage, the bottom and side surfaces of the membrane tank have a secondary barrier which is an additional membrane installed inside the heat-insulating layer.

[0052] The storage tanks for WFLH and SGC are formed by GBS concrete sections 15 and 16, and their boundary structures function as barriers.

[0053] As consumable, chemical, and waste tanks (e.g., diesel, oil, mud, tap water, glycol solution, drilling cuttings, drilling wastewater, demineralized water, fresh water, etc.), smaller storage compartments 19, 20, and 21 are located along the short ends of the GBS.

[0054] Auxiliary compartment 22 and engineering compartment 23 within the central part 1 of the GBS are located on both sides of and centrally between the main LNG, WFLH, and SGC storage compartments 14, 15, and 16. These compartments are intended for processing needs, equipment, fluids used, as well as access and evacuation routes for personnel. In the drying compartment along the periphery of the main compartment for hydrocarbon storage, the outer surfaces of the boundary walls of compartments 14, 15, and 16 (LNG, WFLH, and SGC storage tanks) can be inspected.

[0055] Engineering equipment includes a power supply system including a substation, a heating, ventilation, and air conditioning (HVAC) system, a ballast water heating and recirculation system, a water supply and drainage system, fire pumps and pipelines, a foam fire extinguishing system skid, an electrochemical corrosion prevention system, an electrical communication and alarm system, and a video surveillance system. Most of the engineering equipment is located above the upper slab 3 and / or in / above the processing module 12, and the remaining part is located within the engineering compartment 23. The auxiliary compartment 22 is always kept empty and can be made accessible by means of ladders and manholes for assistance.

[0056] The support load is transmitted from the drilling rig 10, flare unit 11, processing module 12, and residential module 13 to the main load-bearing structure of the GBS by the reinforced concrete support 7 for the upper deck module on the GBS upper slab 3. Structurally, the support 7 is a reinforced concrete pylon having a head portion for an embedded component.

[0057] The position of the reinforced concrete support 7 corresponds to the intersection of the GBS vertical wall 6 that enables the dispersion of the load from the upper deck module.

[0058] The reinforced concrete support 7 is necessary to install pipes and cables 24 between the upper deck and the equipment within the GBS section, and to ensure access for people and vehicles across the entire GBS upper slab 3. Therefore, it is designed to be tall enough to provide sufficient space between the GBS upper slab 3 and the bottom of the excavation rig 10, flare 11, processing module 12, and residential module 13.

[0059] The GBS ballast system includes the inner ballast compartments 17 formed by the vertical walls 6, including the compartments under the intermediate slab 5, as well as the outer ballast compartments 17 of the GBS central part 1 and GBS protrusion 2 respectively. To prevent the water in the ballast compartments 17 from freezing, this design is equipped with a ballast recirculation and heating system. The water in the ballast compartments 17 is heated using the waste heat from the flue gas of the gas turbines installed in the upper deck module.

[0060] The ballast system performs the following two main functions: Ballast treatment, that is, changing the weight of the GBS to ensure the draft of the GBS required during floating and the structural stability when the GBS is installed on the foundation 9. GBS balancing, that is, stabilizing the GBS without roll and trim during floating by compensating for the deviation of the structural center of gravity from the geometric center with ballast water.

[0061] The upper deck is equipped with processing equipment composed of the processing module 12. The number of processing modules 12 is determined during the engineering stage of the production complex facility. The positions of the modules on the GBS are considered in terms of their weights, and it is assumed that the center of gravity of the GDCPSO will be close to the geometric center of the GBS so as to reduce the volume of water ballast required to balance the structure during floating.

[0062] The processing module 12 is a three-dimensional steel frame with braces that houses processing equipment, electrical equipment, automation systems, etc.

[0063] At the basic level, the processing module 12 does not differ from the upper deck modules used in the oil and gas sector in other types of marine oil and gas structures in terms of their design and layout.

[0064] The processing module houses processing equipment for the purification and treatment of raw gas, gas liquefaction equipment, equipment for loading LNG, WFLH, and SGC onto tankers, as well as auxiliary equipment and utilities.

[0065] The processing system for the treatment and utilization of the raw materials produced from the wells is designed to act on the formation fluids to produce gas, WFLH, and stabilized gas condensate. These systems are similar to those commonly used in onshore oil fields. The difference is that marine equipment is used.

[0066] To facilitate equipment maintenance and personnel access, each processing module 12 has several levels (decks). The main level 8 of each processing module 12 is at the same height to enable a combination of evacuation routes and load transfer routes across the upper deck, thus reducing the load on the GBS upper slab 3. The other levels of the processing module 12 have different heights according to their functions and equipment.

[0067] The jetty 25 for loading LNG, WFLH, and SGC is structurally integrated with the GBS and the upper deck and is located along both long sides of the GBS. The jetty 25 is equipped with a loading platform with mooring fenders, bracers, and loading arms, as well as other marine equipment and processing equipment enabling loading. The drawing shows the water level 26 in the water area.

[0068] The compartments may be separated by transverse partitions except for the main LNG storage compartment 14. Openings for water flow may be made inside the walls of the ballast compartment 17, and passages for personnel and penetrations for wiring and piping may be made in the engineering compartments 22 and 23.

[0069] The drilling facility is designed for the operating conditions in the offshore oilfield and has relevant climate design. To ensure the operations related to well drilling, the drilling facility includes a handling device, blowout preventer equipment, mud pumps, mud circulation system, concrete placing facility, pneumatic conveying system, slurry preparation and injection system, drilling wastewater collection system, a hydraulic actuated gear for the mechanism of the drilling rig 10, a bulk material storage, etc., and is equipped with a drilling rig 10 (Figs. 1 and 4).

[0070] The drilling rig 10 of the GDCPSO ensures multiple well drillings and repairs throughout the year for vertical wells, deviated wells, and horizontal wells. By moving the drilling rig 10 across the entire well pattern, multiple well drillings are ensured.

[0071] The drilling rig 10 is installed at the short end of the central part 1 of the GBS, and the section 18 below it functions as a borehole well.

[0072] The drilling rig 10 is equipped with a base frame having an infrastructure to which equipment and systems for ensuring well drilling are attached. The handling device of the drilling rig 10 enables the drilling rig 10 to be positioned above and fixed at any point of the well pattern. Drilling is carried out through the borehole well 18 of the GBS (Figs. 4 - 7).

[0073] The processing system for well fluid treatment and disposal is designed to operate as part of the integrated GDCPSO.

[0074] This design includes high - pressure and low - pressure flare systems for safely disposing of gases containing hydrocarbon gas / steam generated from high - pressure and low - pressure processing equipment respectively, which are not consumed for power or heat production. The flare system is also involved during emergencies and / or blowdowns. Gases from the high - pressure and low - pressure systems are sent to the flare unit 11 and burned at the flare tip (Figs. 1 and 3).

[0075] The residential area module 13 is used to provide accommodation facilities (Figs. 1, 3, and 4). The residential area module 13 is a safe, fully functional, fire-resistant, and securely fixed building that meets all applicable architectural, design, sanitary, and general technical requirements. The residential area module 13 is developed as part of the upper deck together with other structures and systems.

[0076] The residential area module 13 is a fully functional modular structure that includes buildings for living, public use, sanitation, medical care, and dining, as well as buildings for auxiliary equipment to support the functions of the residential area module 13.

[0077] In accordance with safety requirements, the residential area module 13 is installed as far as possible from the most dangerous operating area where the excavation facility 10 is located.

Claims

1. An offshore production complex for the extraction, treatment, and processing of raw gas, comprising an infrastructure with an upper deck located on top, wherein the upper deck comprises a drilling facility, a flare unit, processing equipment for the treatment and processing of raw gas, and a residential area, the infrastructure houses storage tanks for corresponding processed production products, the infrastructure is a gravity-based structure (GBS) having a central part and a protruding part, the central part is a rectangular column having an upper slab on which the processing equipment is located, the GBS protruding part extends along the entire perimeter along the side of the central part and has a vertical outer wall, the central part and the protruding part share a base slab, the height of the protruding part is lower than that of the central part, the GBS central part has vertical and horizontal walls forming compartments including a ballast compartment and a compartment for housing storage tanks for corresponding processed production products, and the GBS protruding part has an inner wall perpendicular to its outer wall and forming a ballast compartment. An offshore production complex characterized by the above.

2. The offshore production complex according to claim 1, wherein the drilling facility comprises a drilling rig installed at the short end of the GBS central part, and the compartment below the drilling rig functions as a borehole well.

3. The offshore production complex according to claim 1, wherein the compartment formed by the short end wall on one side of the GBS central part includes at least one consumable compartment, at least one chemical compartment, and at least one waste compartment.

4. The offshore production complex according to claim 1, wherein a part of the compartments within the GBS central part, including at least one of the compartments formed by the short end wall on one side of the central part, is an auxiliary compartment.

5. The offshore production complex according to claim 1, wherein the GBS central part also has, in a position located above it, an intermediate horizontal slab storage tank for the corresponding processed production product, i.e., liquefied natural gas, and there are vertical and horizontal walls forming an additional ballast compartment between the intermediate horizontal slab and the base slab.

6. The offshore production complex according to claim 5, wherein a part of the compartments within the GBS central part forms storage tanks for other corresponding processed production products, i.e., stable gas condensate and a wide range of light hydrocarbons.

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