Patent Grant
9957446
This invention relates to systems, apparatuses, and methods used to dehydrate crude oil for storage in crude oil storage tanks of floating production storage and offloading (“FPSO”) installations. More specifically, the invention relates to a process train that includes a compact electrostatic separator.
Conventional topside oil separation trains on FPSO installations employ multiple three-phase separators, which separate oil, water, and gas. These three-phase separators are typically large, heavy, and require a significant residence volume to achieve the required separation. In addition, the three-phase separators require significant space because they must be positioned horizontally within the process train.
FPSO installations have limitations on the amount of space that is available and the amount of weight that they are able to support. As a result, there is a need for systems to reduce the space and weight of the equipment required for process trains without compromising the effectiveness and efficiency of the treatment process.
A system for dehydrating crude oil on a FPSO installation includes a separator vessel to receive an incoming produced water stream, followed by a flash vessel, a treatment block, a crude oil storage tank, and an electrostatic treater. The treatment block includes a low pressure degasser followed by a compact electrostatic separator pre-treater or a compact electrostatic separator pre-treater followed by a low pressure degasser. The flash vessel and/or the low pressure degasser may employ an inlet cyclonic distributor and demisting cyclones, while the electrostatic treater may employ DUAL FREQUENCY® technology. The separator vessel may be a single two-phase separator/degasser or two two-phase separator/degassers that operate in parallel with each receiving approximately 50 percent of the incoming produced water stream.
A method for dehydrating crude oil on a FPSO installation includes routing an incoming produced water stream to a separator vessel, routing the outlet stream from the separator vessel to a flash vessel, routing the outlet stream from the flash vessel to a treatment block, routing the outlet stream from the treatment block to a crude oil storage tank, and routing the outlet stream from the crude oil storage tank to an electrostatic treater. Within the treatment block, the outlet stream from the flash vessel is routed to a low pressure degasser and a compact electrostatic separator pre-treater or to a compact electrostatic separator pre-treater and a low pressure degasser. The separator vessel may be a single two-phase separator/degasser or two two-phase separator/degassers that operate in parallel. The final outlet stream preferably contains no more than 0.5 BS&W and 285 milligrams per liter salt.
Objectives of this invention include providing systems and methods that reduce the size and weight requirements of prior art FPSO process trains without compromising treatment performance.
Employing a compact electrostatic separator in the process train allows all of the early stages of separation to be two-phase rather than three-phase. This minimizes the different types of equipment that are required, makes the individual components of the process train smaller, and allows the process vessels to be positioned vertically within the process train, thereby reducing its overall footprint and weight.
For the purpose of comparison to the preferred embodiments, the prior art topside process train of
The train is designed to achieve a maximum total liquids flow rate of 24,000 m3/day (150,000 bpd), a maximum oil flow rate of 24,000 m3/day (150,000 bpd), a maximum produced water flow rate of 19,100 m3/day (120,000 bpd), and maximum gas flow rate of 6,000,000 m3/day. The incoming crude oil properties are 27 API; viscosity 47.1, 30.3 and 19.9 cSt at 30°, 40°, and 50° C. respectively; initial paraffin deposit temperature of 40° C. first event and 20° C. second event; pour point of 12° C.; and severe foaming. The oil temperature on arrival to the train is in a range of 20° C. (maximum oil cases) to 40° C. (maximum water cases).
The size and weight requirements of the prior art train are shown in Table 2. The train, not including the crude oil storage tank, requires a plot area of 275 m2, with a dry weight of 353.4 tonnes and an operating weight of 1047.4 tonnes. Note the amount of water-in-oil decreases at each successive processing step, with 25% water content in the outlet stream of the high pressure separator to a 1% water content in the inlet stream to the low pressure degasser.
Referring now to
Compared to the prior art train of
Referring to
The outlet stream 25 from the high pressure separator 20 is routed to the intermediate pressure flash vessel 30, which may have a CONSEPT® inlet cyclonic distributor (Cameron Solutions, Inc., Houston, Tex.) and demisting cyclones. Using the CONSEPT® inlet cyclonic distributor, which has a liquid hold-up time of only thirty seconds, allows the intermediate pressure flash vessel 30 to be vertically situated within the process train 10, with significant reductions in the space and weight of the process train 10.
The outlet stream 35 from the intermediate pressure flash vessel 30 is then routed to the low pressure degasser 40, which may also have an CONSEPT® inlet cyclonic distributor and demisting cyclones. Using the CONSEPT® inlet cyclonic distributor allows the low pressure degasser 40 to be vertically situated within the process train 10, with significant reductions in the space and weight of the process train 10.
The outlet stream 45 from the low pressure degasser 40 is routed to the compact electrostatic separator pre-treater 50. The pre-treater 50 includes at least two elongated separator vessels oriented at an incline and connected to one another so that an upwardly flowing oil-predominant fluid passes from the first separator vessel to the second separator vessel where further electrostatic separation of water from the oil-predominant fluid occurs. Each vessel has an electrode at its upper end preferably connected to a different voltage source. The inlet to each vessel is located relative to the electrode to provide an up flow or a down flow vessel. Additionally, the first vessel may be at a different elevation than the second vessel. An additional vessel may be included with output from the first vessel bypassing the additional vessel, the second vessel, or both. Baffles may be added in the water collection portion of each vessel to reduce turbulence and settling distances. The compact electrostatic separator pre-treater 50 is further described in U.S. Pat. No. 9,095,790 B2, the contents of which are incorporated herein by reference.
The compact electrostatic separator pre-treater 50 may take an inlet water cut of 20.8 to 28% water-in-oil and reduce it to between 3 to 10% water-in-oil. This pre-treater 50 is also a vertical unit, which further reduces the space and weight of the process train 10 compared to the prior art process train in
The outlet stream 55 from the compact electrostatic separator pre-treater 50 is routed to the cargo tank 60, where it is de-watered from 3 to 10% water-in-oil to 1% water-in-oil. The cargo tank 60 may be any size and type that are well known in the art.
The outlet stream 65 from the cargo tank 60 is routed to the electrostatic treater 70. The electrostatic treater employs DUAL FREQUENCY® technology (Cameron Solutions, Inc., Houston, Tex.) as described in U.S. Pat. Nos. 6,860,979 B2 and 7,351,320 B2, the contents of which are herein incorporated by reference. This technology includes passing the oil-water emulsion into a treatment vessel, establishing at least one dual frequency electric field within the vessel, and selectably varying the electric field at a first frequency modulated in intensity at a second frequency where the first frequency is greater than the second. Preferably, the BS&W content of the stream 75 exiting the electrostatic treater 70 is no greater than 0.5% BS&W and 285 mg/l salt.
Referring now to
The equipment for each component of the process train in
Referring now to
Compared to the prior art train of
Referring to
The outlet stream 125 from the high pressure separator/degasser 120 is routed to the intermediate pressure flash vessel 30, which may have a CONSEPT® inlet cyclonic distributor (Cameron Solutions, Inc., Houston, Tex.) and demisting cyclones. Using the CONSEPT® inlet cyclonic distributor, which has a liquid hold-up time of only thirty seconds, allows the intermediate pressure flash vessel 30 to be vertically situated within the process train 110, with significant reductions in the space and weight of the process train 110.
The outlet stream 130 from the intermediate pressure flash vessel 30 is then routed to the low pressure degasser 40, which may also have an CONSEPT® inlet cyclonic distributor and demisting cyclones. Using the CONSEPT® inlet cyclonic distributor allows the low pressure degasser 40 to be vertically situated within the process train 110, with significant reductions in the space and weight of the process train 110.
The outlet stream 135 from the low pressure degasser 40 is routed to the compact electrostatic separator pre-treater 50. The pre-treater 50 includes at least two elongated separator vessels oriented at an incline and connected to one another so that an upwardly flowing oil-predominant fluid passes from the first separator vessel to the second separator vessel where further electrostatic separation of water from the oil-predominant fluid occurs. Each vessel has an electrode at its upper end preferably connected to a different voltage source. The inlet to each vessel is located relative to the electrode to provide an up flow or a down flow vessel. Additionally, the first vessel may be at a different elevation than the second vessel. An additional vessel may be included with output from the first vessel bypassing the additional vessel, the second vessel, or both. Baffles may be added in the water collection portion of each vessel to reduce turbulence and settling distances. The compact electrostatic separator pre-treater 50 is further described in U.S. Pat. No. 9,095,790 B2, the contents of which are incorporated herein by reference.
The compact electrostatic separator pre-treater 50 may take an inlet water cut of 20 to 80% water-in-oil and reduce it to between 3 to 10% water-in-oil. This pre-treater 50 is also a vertical unit, which further reduces the space and weight of the process train 110 compared to the prior art process train in
The outlet stream 140 from the compact electrostatic separator pre-treater 50 is routed to the cargo tank 60, where it is de-watered from 3 to 10% water-in-oil to 1% water-in-oil. The cargo tank 60 may be any size and type that are well known in the art.
The outlet stream 145 from the cargo tank 60 is routed to the electrostatic treater 70. The electrostatic treater 70 employs DUAL FREQUENCY® technology (Cameron Solutions, Inc., Houston, Tex.) as described in U.S. Pat. Nos. 6,860,979 B2 and 7,351,320 B2, the contents of which are herein incorporated by reference. This technology includes passing the oil-water emulsion into a treatment vessel, establishing at least one dual frequency electric field within the vessel, and selectably varying the electric field at a first frequency modulated in intensity at a second frequency where the first frequency is greater than the second. Preferably, the BS&W content of the stream 150 as it exits the electrostatic treater 70 is no greater than 0.5% BS&W and 285 mg/l salt.
Referring now to
The equipment for each component of the process train in
Referring now to
Compared to the prior art train of
Referring to
The outlet streams 205 from the high pressure separator/degassers 200 are combined and routed to the intermediate pressure flash vessel 30, which may have a CONSEPT® inlet cyclonic distributor (Cameron Solutions, Inc., Houston, Tex.) and demisting cyclones. Using the CONSEPT® inlet cyclonic distributor, which has a liquid hold-up time of only thirty seconds, allows the intermediate pressure flash vessel 30 to be vertically situated within the process train 190, with significant reductions in the space and weight of the process train 190.
The outlet stream 210 from the intermediate pressure flash vessel 30 is then routed to the low pressure degasser 40, which may also have an CONSEPT® inlet cyclonic distributor and demisting cyclones. Using the CONSEPT® inlet cyclonic distributor allows the low pressure degasser 40 to be vertically situated within the process train 190, with significant reductions in the space and weight of the process train 190.
The outlet stream 220 from the low pressure degasser 40 is routed to the compact electrostatic separator pre-treater 50. The pre-treater 50 includes at least two elongated separator vessels oriented at an incline and connected to one another so that an upwardly flowing oil-predominant fluid passes from the first separator vessel to the second separator vessel where further electrostatic separation of water from the oil-predominant fluid occurs. Each vessel has an electrode at its upper end preferably connected to a different voltage source. The inlet to each vessel is located relative to the electrode to provide an up flow or adown flow vessel. Additionally, the first vessel may be at a different elevation than the second vessel. An additional vessel may be included with output from the first vessel bypassing the additional vessel, the second vessel, or both. Baffles may be added in the water collection portion of each vessel to reduce turbulence and settling distances. The compact electrostatic separator pre-treater 50 is further described in U.S. Pat. No. 9,095,790 B2, the contents of which are incorporated herein by reference.
The compact electrostatic separator pre-treater 50 may take an inlet water cut of 20.8 to 28% water-in-oil and reduce it to between 3 to 10% water-in-oil. This pre-treater 50 is also a vertical unit, which further reduces the space and weight of the process train 190 compared to the prior art process train in
The outlet stream 230 from the compact electrostatic separator pre-treater 50 is routed to the cargo tank 60, where it is de-watered from 3 to 10% water-in-oil to 1% water-in-oil. The cargo tank 60 may be any size and type that are well known in the art. The outlet stream 240 from the cargo tank 60 is routed to the electrostatic treater 70. The electrostatic treater employs DUAL FREQUENCY® technology (Cameron Solutions, Inc., Houston, Tex.) as described in U.S. Pat. Nos. 6,860,979 B2 and 7,351,320 B2, the contents of which are herein incorporated by reference. This technology includes passing the oil-water emulsion into a treatment vessel, establishing at least one dual frequency electric field within the vessel, and selectably varying the electric field at a first frequency modulated in intensity at a second frequency where the first frequency is greater than the second. Preferably, the BS&W content of the stream 250 as it exits the electrostatic treater 70 is no greater than 0.5% BS&W and 285 mg/l salt.
Referring now to
The equipment for each component of the process train in
While the invention has been described with a certain degree of particularity, many changes may be made in the details of construction, the arrangement of components, the steps of the process, and the order of the steps without departing from the spirit and scope of this disclosure. Further, multiple systems may be operated in parallel. The invention is not limited to the embodiments set forth herein for purposes of exemplification, but is limited only by the scope of the attached claims, including the full range of equivalency to which each element thereof is entitled.
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