Abstract:
A system and method for dehydrating crude oil on a floating production storage and offloading installation include 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 horizontal two-phase separator/degasser or two vertical two-phase separator/degassers that operate in parallel with each receiving approximately 50 percent of the incoming produced water stream. The final outlet stream preferably contains no more than 0.5 BS&amp;W and 285 milligrams per liter salt.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    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. 
         [0002]    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. 
         [0003]    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. 
       SUMMARY OF THE INVENTION 
       [0004]    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. 
         [0005]    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&amp;W and 285 milligrams per liter salt. 
         [0006]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a block flow diagram of a prior art topside process train. 
           [0008]      FIG. 2  is a block flow diagram of a preferred embodiment of a topside process train that practices the system and method of this invention, showing the high pressure separator, the intermediate flash vessel, the low pressure degasser, the compact electrostatic separator pre-treater, the crude oil storage tank, and the electrostatic treater in the process train. 
           [0009]      FIG. 3  is a block flow diagram of a preferred embodiment of a topside process train that practices the system and method of this invention, showing the high pressure separator, the intermediate pressure flash vessel, the compact electrostatic separator pre-treater, the low pressure degasser, the crude oil storage tank, and the electrostatic treater in the process train. 
           [0010]      FIG. 4  is a block flow diagram of a preferred embodiment of a topside process train that practices the system and method of this invention, showing the high pressure separator/degasser, the intermediate pressure flash vessel, the low pressure degasser, the compact electrostatic separator pre-treater, the crude oil storage tank, and the electrostatic treater in the process train. 
           [0011]      FIG. 5  is a block flow diagram of a preferred embodiment of a topside process train that practices the system and method of this invention, showing the high pressure separator/degasser, the intermediate pressure flash vessel, the compact electrostatic separator pre-treater, the low pressure degasser, the crude oil storage tank, and the electrostatic treater in the process train. 
           [0012]      FIG. 6  is a block flow diagram of a preferred embodiment of a topside process train that practices the system and method of this invention, showing two high pressure separator/degassers in parallel, the intermediate pressure flash vessel, the low pressure degasser, the compact electrostatic separator pre-treater, the crude oil storage tank, and the electrostatic treater in the process train. 
           [0013]      FIG. 7  is a block flow diagram of a preferred embodiment of a topside process train that practices the system and method of this invention, showing two high pressure separator/degassers in parallel, the intermediate pressure flash vessel, the compact electrostatic separator pre-treater, the low pressure degasser, the crude oil storage tank, and the electrostatic treater in the process train. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]    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. 
         [0015]    For the purpose of comparison to the preferred embodiments, the prior art topside process train of  FIG. 1  is used. This prior art train includes a high pressure separator, an intermediate pressure flash vessel (mounted on the pre-treater), a pre-treater, a low pressure degasser (mounted on the electrostatic treater), and an electrostatic treater (see Table 1). The train also includes a crude oil storage tank located downstream of the electrostatic treater. 
         [0000]    
       
         
               
             
               
               
             
               
             
               
               
             
               
             
               
               
             
               
             
               
               
             
               
             
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Prior art process train. 
               
               
                   
               
             
             
               
                 HP Separator 
               
             
          
           
               
                 Operating Pressure: 
                 2,000 kPa (a) 
               
               
                 Operating Temperature: 
                 40° C. 
               
               
                 Slug volume: 
                 20 m 3   
               
               
                 Maximum Water Content in Crude Outlet: 
                 25% vol 
               
               
                 Size: 
                 4.4 m ID × 16.0 m T/T 
               
               
                   
                 Horizontal 
               
             
          
           
               
                 IP Flash Vessel (mounted on Pre-treater) 
               
             
          
           
               
                 Operating Pressure: 
                 770 kPa (a) 
               
               
                 Operating Temperature: 
                 90° C. 
               
               
                 Liquid Hold Up: 
                 2 Minutes 
               
               
                 Size: 
                 3.3 m ID × 10.0 m T/T 
               
               
                   
                 Horizontal mounted on 
               
               
                   
                 Pre-treater 
               
             
          
           
               
                 Pre-Treater 
               
             
          
           
               
                 Operating Pressure: 
                 770 kPa (a) 
               
               
                 Operating Temperature: 
                 90° C. 
               
               
                 Maximum Water Content in Crude Outlet: 
                 1% vol 
               
               
                 Size: 
                 3.3 m ID × 10.0 m T/T 
               
               
                   
                 Horizontal 
               
             
          
           
               
                 LP Degasser (mounted on Electrostatic Treater) 
               
             
          
           
               
                 Operating Pressure: 
                 250 kPa (a) 
               
               
                 Operating Temperature: 
                 75-80° C. 
               
               
                 Liquid Hold Up: 
                 2 Minutes 
               
               
                 Size: 
                 33 m ID × 10.0 m T/T 
               
               
                   
                 Horizontal mounted on 
               
               
                   
                 Pre-treater 
               
             
          
           
               
                 Electrostatic Treater 
               
             
          
           
               
                 Operating Pressure: 
                 250 kPa (a) 
               
               
                 Operating Temperature: 
                 75-80° C. 
               
               
                 Maximum Water Content in Crude Outlet: 
                 0.5% vol 
               
               
                 Maximum Salt content in Crude Outlet: 
                 285 mg/l 
               
               
                   
               
             
          
         
       
     
         [0016]    The train is designed to achieve a maximum total liquids flow rate of 24,000 m 3 /day (150,000 bpd), a maximum oil flow rate of 24,000 m 3 /day (150,000 bpd), a maximum produced water flow rate of 19,100 m 3 /day (120,000 bpd), and maximum gas flow rate of 6,000,000 m 3 /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). 
         [0017]    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 m 2 , 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. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Size and weight requirements of prior art process train. 
               
             
          
           
               
                   
                   
                   
                   
                 Plot 
                   
               
               
                 Equipment 
                 Technology &amp; 
                   
                 Size 
                 Area 
                 Weights 
               
               
                 Item 
                 Performance 
                 Residence Requirements 
                 (ID × T/T) 
                 (m 2 ) 
                 (Tonnes) 
               
               
                   
               
             
          
           
               
                 HP Separator 
                 Existing 2/3-Phase 
                 2 Phase: 
                 4.4 m × 16 m 
                 95 
                 117.5 
                 Dry 
               
               
                   
                 Separator 
                 2 Mins Liquids @ 1255 m 3 /hr = 
                 Horizontal 
                   
                 302.5 
                 Op. 
               
               
                   
                 Inlet: 
                 41.83 m 3   
               
               
                   
                 20-80% Water, 
                 3 Phase: 
               
               
                   
                 80-20% Oil 
                 5 minutes Oil @ 1061 m 3 /hr = 
               
               
                   
                 Outlet: 
                 88.4 m 3   
               
               
                   
                 25% Water-in-Oil 
                 5 minutes Water @ 794 m 3 /hr = 
               
               
                   
                   
                 66.2 m 3   
               
               
                   
                   
                 20 m 3  Surge both 2 &amp; 3 phase 
               
               
                 IP Flash Vessel 
                 Existing Design 
                 2 minutes @ 1346 m 3 /hr = 44.8 m 3   
                 3.3 m × 10 m 
                 Inc. 
                 39.4 
                 Dry 
               
               
                   
                 Inlet: 
                   
                 Horizontal 
                 Below 
                 92.4 
                 Op. 
               
               
                   
                 20.8-28% Water-in-Oil 
               
               
                 Pre-Treater 
                 Existing Electrostatic 
                 As Required for Spec 
                 4.2 m × 16 m 
                 90 
                 83.8 
                 Dry 
               
               
                   
                 Technology Outlet: 
                   
                 Horizontal 
                   
                 286.8 
                 Op. 
               
               
                   
                 1% Water-in-Oil 
               
               
                 LP Degasser 
                 Existing Design 
                 2 minutes @ 1159 m 3 /hr = 38.6 m 3   
                 3.2 m × 10 m 
                 Inc. 
                 30.5 
                 Dry 
               
               
                   
                 Inlet: 
                   
                 Horizontal 
                 Below 
                 77.5 
                 Op. 
               
               
                   
                 1% Water-in-Oil 
               
               
                 Electrostatic 
                 Existing Electrostatic 
                 As Required for Spec 
                 4.2 m × 16 m 
                 90 
                 82.2 
                 Dry 
               
               
                 Treater 
                 Technology Desalter + 
                   
                 Horizontal 
                   
                 288.2 
                 Op. 
               
               
                   
                 100 m 3 /hr Wash Water 
               
               
                   
                 Outlet: 
               
               
                   
                 0.5% BS&amp;W 
               
               
                   
                 285 mg/l Salt 
                   
                   
                   
                   
               
               
                 Total 
                 — 
                 — 
                 — 
                 275  
                 353.4 
                 Dry 
               
               
                   
                   
                   
                   
                   
                 1047.4 
                 Op. 
               
               
                   
               
             
          
         
       
     
         [0018]    Referring now to  FIG. 2 , a preferred embodiment of a topside process train  10  includes a high pressure separator  20 , an intermediate pressure flash vessel  30  arranged downstream of the high pressure separator  20 , a low pressure degasser  40  arranged downstream of the intermediate pressure flash vessel  30 , a compact electrostatic separator pre-treater  50  arranged downstream of the low pressure degasser  40 , a crude oil storage tank (“cargo tank”)  60  arranged downstream of the compact electrostatic separator pre-treater  50 , and, finally, an electrostatic treater  70  arranged downstream of the cargo tank  60 . 
         [0019]    Compared to the prior art train of  FIG. 1 , the process train of  FIG. 2 , excluding the cargo tank, has a plot area of 177 m 2 , thereby reducing space requirements by 103 m 2  (a 37% reduction), and a dry weight of 178.8 tonnes, thereby reducing the total dry weight by 176.2 tonnes (a 50% reduction, with operating weight reduced by 513.3 tonnes or 49%). 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Preferred embodiment of the process train. 
               
             
          
           
               
                 Equipment 
                 Technology &amp; 
                 Residence 
                 Size 
                 Plot Area 
                 Plot Area 
                 Weights 
                 Weight 
               
               
                 Item 
                 Performance 
                 Rqmts. 
                 (ID × T/T) 
                 (m 2 ) 
                 Reduction 
                 (Tonnes) 
                 Reduction 
               
               
                   
               
             
          
           
               
                 HP 
                 Existing 2/3-Phase 
                 2 Phase: 
                 4.4 m × 16 m 
                 ≈95 
                 n/a 
                 117.5 
                 Dry 
                 n/a 
                 Dry 
               
               
                 Separator 
                 Separator 
                 2 Mins 
                 Horizontal 
                   
                   
                 302.5 
                 Op. 
                 n/a 
                 Op. 
               
               
                   
                 Inlet: 
                 Liquids @ 
               
               
                   
                 20-80% Water, 
                 1255 m 3 /hr = 
               
               
                   
                 80-20% Oil 
                 41.83 m 3   
               
               
                   
                 Outlet: 
                 3 Phase: 
               
               
                   
                 25% Water-in-Oil 
                 5 minutes 
               
               
                   
                   
                 Oil @ 1061 m 3 /hr = 
               
               
                   
                   
                 88.4 m 3   
               
               
                   
                   
                 5 minutes 
               
               
                   
                   
                 Water @ 794 m 3 /hr = 
               
               
                   
                   
                 66.2 m 3   
               
               
                   
                   
                 20 m 3  Surge 
               
               
                   
                   
                 both 2 &amp; 3 
               
               
                   
                   
                 phase 
               
               
                 IP Flash 
                 CONSEPT 
                 Cyclonic 
                 1.6 m × 5.3 m 
                 ≈6 
                 ≈+6 
                 1.4 
                 Dry 
                 −38.0 
                 Dry 
               
               
                 Vessel 
                 Compact Design 
                 degassing 
                 Vertical 
                   
                   
                 3.4 
                 Op. 
                 −89.0 
                 Op. 
               
               
                   
                 Inlet: 
                 with no 
               
               
                   
                 20.8-28% Water- 
                 slug 
               
               
                   
                 in-Oil 
                 volume 
               
               
                   
                   
                 rqmt. 
               
               
                 LP Degasser 
                 CONSEPT 
                 Cyclonic 
                 1.6 m × 5.3 m 
                 ≈6 
                 ≈+6 
                 1.4 
                 Dry 
                 −29.1 
                 Dry 
               
               
                   
                 Compact Design 
                 degassing 
                 Vertical 
                   
                   
                 3.4 
                 Op. 
                 −73.1 
                 Op. 
               
               
                   
                 Inlet: 
                 with no 
               
               
                   
                 20.8-28% Water- 
                 slug 
               
               
                   
                 in-Oil 
                 volume 
               
               
                   
                   
                 rqmt. 
               
               
                 Pre-Treater 
                 Cameron Compact 
                 As required 
                 4.2 m × 3.3 m 
                 ≈25 
                 ≈−70 
                 24.0 
                 Dry 
                 −59.8 
                 Dry 
               
               
                   
                 Electrostatic 
                 for spec. 
                 Vertical 
                   
                   
                 100.5 
                 Op. 
                 −186.3 
                 Op. 
               
               
                   
                 Separator (C.E.S.) 
               
               
                   
                 Technology 
               
               
                   
                 Inlet: 
               
               
                   
                 20.8-28% Water- 
               
               
                   
                 in-Oil 
               
               
                   
                 Outlet: 
               
               
                   
                 3-10% Water-in- 
               
               
                   
                 Oil 
               
             
          
           
               
                 Cargo Tank 
                 Inlet: 
                 Existing 
                 Existing 
                 Existing 
                 n/a 
                 n/a 
                 n/a 
               
               
                   
                 3-10% Water-in- 
               
               
                   
                 Oil 
               
               
                   
                 Outlet: 
               
               
                   
                 1% Water-in-Oil 
               
             
          
           
               
                 Electrostatic 
                 Hi-Flux Dual 
                 As required 
                 4.2 m × 6.1 m 
                 ≈45 
                 ≈−45 
                 34.5 
                 Dry 
                 −49.3 
                 Dry 
               
               
                 Treater 
                 Frequency 
                 for spec. 
                 Horizontal 
                   
                   
                 123.3 
                 Op. 
                 −164.9 
                 Op. 
               
               
                   
                 Electrostatic 
               
               
                   
                 Desalter + 
               
               
                   
                 100 m 3 /hr Wash 
               
               
                   
                 Water Outlet: 
               
               
                   
                 0.5% BS&amp;W 
               
               
                   
                 285 mg/l Salt 
                   
                   
                   
                   
                   
                   
               
               
                 Total 
                 — 
                 — 
                 — 
                 177 
                 ≈−103 
                 178.8 
                 Dry 
                 −176.2 
                 Dry 
               
               
                   
                   
                   
                   
                   
                   
                 533.1 
                 Op. 
                 −513.3 
                 Op. 
               
               
                   
               
             
          
         
       
     
         [0020]    Referring to  FIG. 2 , the high pressure separator  20  for this embodiment has the same characteristics, requirements, and performance as the high pressure separator in the prior art process train shown in  FIG. 1 . The high pressure separator  20  receives a mixed process stream  15  that may contain from 20 to 80% water and from 80 to 20% oil. 
         [0021]    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 . 
         [0022]    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 . 
         [0023]    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. 
         [0024]    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  FIG. 1 . 
         [0025]    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. 
         [0026]    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. No. 6,860,979 B2 and U.S. Pat. No. 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&amp;W content of the stream  75  exiting the electrostatic treater  70  is no greater than 0.5% BS&amp;W and 285 mg/l salt. 
         [0027]    Referring now to  FIG. 3 , another preferred embodiment of a topside process train  80  includes a high pressure separator  20  that receives a mixed stream  15  containing 20 to 80% water and 80 to 20% oil, an intermediate pressure flash vessel  30  arranged downstream of the high pressure separator  20  that receives the outlet stream  25  from the high pressure separator  20 , a compact electrostatic separator pre-treater  50  arranged downstream of the intermediate pressure flash vessel  30  that receives the outlet stream  35  from the intermediate pressure flash vessel  30 , a low pressure degasser  40  arranged downstream of the compact electrostatic separator pre-treater  50  that receives the outlet stream  85  from the pre-treater  50 , a crude oil storage tank (“cargo tank”)  60  arranged downstream of the low pressure degasser  40  that receives the outlet stream  90  from the low pressure degasser  40 , and, finally, an electrostatic treater  70  arranged downstream of the cargo tank  60  that receives the outlet stream  95  from the cargo tank  60 . 
         [0028]    The equipment for each component of the process train in  FIG. 3  is the same as the equipment for the process train described in  FIG. 2  and Table 3, with the same advantages in reduced space and weight, and the size of the low pressure degasser  40  is not affected by the relative position of the compact electrostatic separator pre-treater  50 . Preferably, the BS&amp;W content of the stream  100  as it exits the process train  80  is no greater than 0.5% BS&amp;W and 285 mg/l salt. 
         [0029]    Referring now to  FIG. 4 , a preferred embodiment of a topside process train  110  includes a high pressure separator/degasser  120 , an intermediate pressure flash vessel  30  arranged downstream of the high pressure separator/degasser  120 , a low pressure degasser  40  arranged downstream of the intermediate pressure flash vessel  30 , a compact electrostatic separator pre-treater  50  arranged downstream of the low pressure degasser  40 , a crude oil storage tank (“cargo tank”)  60  arranged downstream of the compact electrostatic separator pre-treater  50 , and, finally, an electrostatic treater  70  arranged downstream of the cargo tank  60 . 
         [0030]    Compared to the prior art train of  FIG. 1 , the process train of  FIG. 4 , excluding the cargo tank, has a plot area of 137 m 2 , thereby reducing space requirements by 138 m 2  (a 50% reduction), and a dry weight of 101.3 tonnes, thereby reducing the total dry weight by 253.7 tonnes (a 72% reduction, with operating weight reduced by 765.8 tonnes or 73%). 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Preferred embodiment of the process train. 
               
             
          
           
               
                 Equipment 
                 Technology &amp; 
                 Residence 
                 Size 
                 Plot Area 
                 Plot Area 
                 Weights 
                 Weight 
               
               
                 Item 
                 Performance 
                 Rqmts. 
                 (ID × T/T) 
                 (m 2 ) 
                 Reduction 
                 (Tonnes) 
                 Reduction 
               
               
                   
               
             
          
           
               
                 HP 
                 CONSEPT Compact 
                 30 seconds 
                 3.2 m × 11.2 m 
                 ≈55 
                 ≈−40 
                 40.0 
                 Dry 
                 −77.5 
                 Dry 
               
               
                 Separator/ 
                 Design 
                 liquid 
                 Horizontal 
                   
                   
                 50.0 
                 Op. 
                 −252.5 
                 Op. 
               
               
                 Degasser 
                 Inlet: 
                 retention 
               
               
                   
                 20-80% Water, 
                 with 
               
               
                   
                 80-20% Oil 
                 cyclonic 
               
               
                   
                   
                 degassing 
               
               
                 IP Flash 
                 CONSEPT 
                 Cyclonic 
                 1.6 m × 5.3 m 
                 ≈6 
                 ≈+6 
                 1.4 
                 Dry 
                 −38.0 
                 Dry 
               
               
                 Vessel 
                 Compact Design 
                 degassing 
                 Vertical 
                   
                   
                 3.4 
                 Op. 
                 −89.0 
                 Op. 
               
               
                   
                 Inlet: 
                 with no 
               
               
                   
                 20-80% Water, 
                 slug 
               
               
                   
                 80-20% Oil 
                 volume 
               
               
                   
                   
                 rqmt. 
               
               
                 LP Degasser 
                 CONSEPT 
                 Cyclonic 
                 1.6 m × 5.3 m 
                 ≈6 
                 ≈+6 
                 1.4 
                 Dry 
                 −29.1 
                 Dry 
               
               
                   
                 Compact Design 
                 degassing 
                 Vertical 
                   
                   
                 3.4 
                 Op. 
                 −73.1 
                 Op. 
               
               
                   
                 Inlet: 
                 with no 
               
               
                   
                 20-80% Water, 
                 slug 
               
               
                   
                 80-20% Oil 
                 volume 
               
               
                   
                   
                 rqmt. 
               
               
                 Pre-Treater 
                 Cameron Compact 
                 As required 
                 4.2 m × 3.3 m 
                 ≈25 
                 ≈−65 
                 24.0 
                 Dry 
                 −59.8 
                 Dry 
               
               
                   
                 Electrostatic 
                 for spec. 
                 Vertical 
                   
                   
                 100.5 
                 Op. 
                 −186.3 
                 Op. 
               
               
                   
                 Separator (C.E.S.) 
               
               
                   
                 Technology 
               
               
                   
                 Inlet: 20-80% 
               
               
                   
                 Water, 
               
               
                   
                 80-20% Oil 
               
               
                   
                 Outlet: 3-10% 
               
               
                   
                 Water-in-Oil 
               
             
          
           
               
                 Cargo Tank 
                 Inlet: 
                 Existing 
                 Existing 
                 Existing 
                 n/a 
                 n/a 
                 n/a 
               
               
                   
                 3-10% Water-in- 
               
               
                   
                 Oil 
               
               
                   
                 Outlet: 
               
               
                   
                 1% Water-in-Oil 
               
             
          
           
               
                 Electrostatic 
                 Hi-Flux Dual 
                 As required 
                 4.2 m × 6.1 m 
                 ≈45 
                 ≈−45 
                 34.5 
                 Dry 
                 −49.3 
                 Dry 
               
               
                 Treater 
                 Frequency 
                 for spec. 
                 Horizontal 
                   
                   
                 123.3 
                 Op. 
                 −164.9 
                 Op. 
               
               
                   
                 Electrostatic 
               
               
                   
                 Desalter + 
               
               
                   
                 100 m 3 /hr Wash 
               
               
                   
                 Water Outlet: 
               
               
                   
                 0.5% BS&amp;W 
               
               
                   
                 285 mg/l Salt 
                   
                   
                   
                   
                   
                   
               
               
                 Total 
                 — 
                 — 
                 — 
                 137 
                 ≈−138 
                 101.3 
                 Dry 
                 −253.7 
                 Dry 
               
               
                   
                   
                   
                   
                   
                   
                 280.6 
                 Op. 
                 −765.8 
                 Op. 
               
               
                   
               
             
          
         
       
     
         [0031]    Referring to  FIG. 4 , the high pressure separator/degasser  120  for this embodiment is in two-phase service and employs a CONSEPT® inlet cyclonic distributor (Cameron Solutions, Inc., Houston, Tex.) and demisting cyclones, which allows for the degassing of stream  15  in a compact vessel with only thirty seconds of liquid retention. Although the high pressure separator/degasser  120  remains in a horizontal position within the process train  110 , both the size and weight of the high pressure separator/degasser  120  are reduced as shown in Table 4. 
         [0032]    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 . 
         [0033]    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 . 
         [0034]    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. 
         [0035]    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  FIG. 1 . 
         [0036]    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. 
         [0037]    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. No. 6,860,979 B2 and U.S. Pat. No. 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&amp;W content of the stream  150  as it exits the electrostatic treater  70  is no greater than 0.5% BS&amp;W and 285 mg/l salt. 
         [0038]    Referring now to  FIG. 5 , another preferred embodiment of a topside process train  160  includes a high pressure separator/degasser  120  that receives a mixed stream  15  containing 20 to 80% water and 80 to 20% oil, an intermediate pressure flash vessel  30  arranged downstream of the high pressure separator/degasser  120  that receives the outlet stream  125  from the high pressure separator/degasser  120 , a compact electrostatic separator pre-treater  50  arranged downstream of the intermediate pressure flash vessel  30  that receives the outlet stream  130  from the intermediate pressure flash vessel  30 , a low pressure degasser  40  arranged downstream of the compact electrostatic separator pre-treater  50  that receives the outlet stream  165  from the pre-treater  50 , a crude oil storage tank (“cargo tank”)  60  arranged downstream of the low pressure degasser  40  that receives the outlet stream  170  from the low pressure degasser  40 , and, finally, an electrostatic treater  70  arranged downstream of the cargo tank  60  that receives the outlet stream  175  from the cargo tank  60 . 
         [0039]    The equipment for each component of the process train in  FIG. 5  is the same as the equipment for the process train described in  FIG. 4  and Table 4, with the same advantages in reduced space and weight, and the size of the low pressure degasser  40  is not affected by the relative position of the compact electrostatic separator pre-treater  50 . Preferably, the BS&amp;W content of the stream  180  as it exits the process train  160  is no greater than 0.5% BS&amp;W and 285 mg/l salt. 
         [0040]    Referring now to  FIG. 6 , a preferred embodiment of a topside process train  190  includes two high pressure separators/degassers  200 , an intermediate pressure flash vessel  30  arranged downstream of the high pressure separators/degassers  200 , a low pressure degasser  40  arranged downstream of the intermediate pressure flash vessel  30 , a compact electrostatic separator pre-treater  50  arranged downstream of the low pressure degasser  40 , a crude oil storage tank (“cargo tank”)  60  arranged downstream of the compact electrostatic separator pre-treater  50 , and, finally, an electrostatic treater  70  arranged downstream of the cargo tank  60 . 
         [0041]    Compared to the prior art train of  FIG. 1 , the process train of  FIG. 6 , excluding the cargo tank, has a plot area of 102 m 2 , thereby reducing space requirements by 173 m 2  (a 63% reduction), and a dry weight of 107.3 tonnes, thereby reducing the total dry weight by 247.7 tonnes (a 70% reduction, with operating weight reduced by 759.8 tonnes or 73%). 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Preferred embodiment of the process train. 
               
             
          
           
               
                 Equipment 
                 Technology &amp; 
                 Residence 
                 Size 
                 Plot Area 
                 Plot Area 
                 Weights 
                 Weight 
               
               
                 Item 
                 Performance 
                 Rqmts. 
                 (ID × T/T) 
                 (m 2 ) 
                 Reduction 
                 (Tonnes) 
                 Reduction 
               
               
                   
               
             
          
           
               
                 HP 
                 CONSEPT Compact 
                 30 seconds 
                 Two (2) 
                 ≈20 
                 ≈−75 
                 46.0 
                 Dry 
                 −71.5 
                 Dry 
               
               
                 Separator/ 
                 Design 
                 liquid 
                 2.5 m × 10.0 m 
                   
                   
                 56.0 
                 Op. 
                 −246.5 
                 Op. 
               
               
                 Degasser 
                 Inlet: 
                 retention 
                 Vertical 
               
               
                 Two (2) × 
                 20-80% Water, 
                 with 
               
               
                 50% 
                 80-20% Oil 
                 cyclonic 
               
               
                   
                   
                 degassing 
               
               
                 IP Flash 
                 CONSEPT 
                 Cyclonic 
                 1.6 m × 5.3 m 
                 ≈6 
                 ≈+6 
                 1.4 
                 Dry 
                 −38.0 
                 Dry 
               
               
                 Vessel 
                 Compact Design 
                 degassing 
                 Vertical 
                   
                   
                 3.4 
                 Op. 
                 −89.0 
                 Op. 
               
               
                   
                 Inlet: 
                 with no 
               
               
                   
                 20-80% Water, 
                 slug 
               
               
                   
                 80-20% Oil 
                 volume 
               
               
                   
                   
                 rqmt. 
               
               
                 LP Degasser 
                 CONSEPT 
                 Cyclonic 
                 1.6 m × 5.3 m 
                 ≈6 
                 ≈+6 
                 1.4 
                 Dry 
                 −29.1 
                 Dry 
               
               
                   
                 Compact Design 
                 degassing 
                 Vertical 
                   
                   
                 3.4 
                 Op. 
                 −73.1 
                 Op. 
               
               
                   
                 Inlet: 
                 with no 
               
               
                   
                 20-80% Water, 
                 slug 
               
               
                   
                 80-20% Oil 
                 volume 
               
               
                   
                   
                 rqmt. 
               
               
                 Pre-Treater 
                 Cameron Compact 
                 As required 
                 4.2 m × 3.3 m 
                 ≈25 
                 ≈−65 
                 24.0 
                 Dry 
                 −59.8 
                 Dry 
               
               
                   
                 Electrostatic 
                 for spec. 
                 Vertical 
                   
                   
                 100.5 
                 Op. 
                 −186.3 
                 Op. 
               
               
                   
                 Separator (C.E.S.) 
               
               
                   
                 Technology 
               
               
                   
                 Inlet: 20.8-28% 
               
               
                   
                 Water-in-Oil 
               
               
                   
                 Outlet: 3-10% 
               
               
                   
                 Water-in-Oil 
               
             
          
           
               
                 Cargo Tank 
                 Inlet: 
                 Existing 
                 Existing 
                 Existing 
                 n/a 
                 n/a 
                 n/a 
               
               
                   
                 3-10% Water-in- 
               
               
                   
                 Oil 
               
               
                   
                 Outlet: 
               
               
                   
                 1% Water-in-Oil 
               
             
          
           
               
                 Electrostatic 
                 Hi-Flux Dual 
                 As required 
                 4.2 m × 6.1 m 
                 ≈45 
                 ≈−45 
                 34.5 
                 Dry 
                 −49.3 
                 Dry 
               
               
                 Treater 
                 Frequency 
                 for spec. 
                 Horizontal 
                   
                   
                 123.3 
                 Op. 
                 −164.9 
                 Op. 
               
               
                   
                 Electrostatic 
               
               
                   
                 Desalter + 
               
               
                   
                 100 m 3 /hr Wash 
               
               
                   
                 Water Outlet: 
               
               
                   
                 0.5% BS&amp;W 
               
               
                   
                 285 mg/l Salt 
                   
                   
                   
                   
                   
                   
               
               
                 Total 
                 — 
                 — 
                 — 
                 102 
                 ≈−173 
                 107.3 
                 Dry 
                 −247.7 
                 Dry 
               
               
                   
                   
                   
                   
                   
                   
                 286.6 
                 Op. 
                 −759.8 
                 Op. 
               
               
                   
               
             
          
         
       
     
         [0042]    Referring to  FIG. 6 , the two high pressure separator/degassers  200  for this embodiment operate in parallel, with each separator/degasser  200  receiving approximately fifty percent of the stream  15 . Each high pressure separator/degasser  200  is in two-phase service and employs a CONSEPT® inlet cyclonic distributor (Cameron Solutions, Inc., Houston, Tex.) and demisting cyclones, which allows for the degassing of the stream  15  in a compact vessel with only thirty seconds of liquid retention. Dividing the stream between the two separator/degassers  200  allows the separator/degassers  200  to be mounted vertically rather than horizontally, thereby reducing the space requirements and weight of the process train  190  as shown in Table 5. 
         [0043]    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 . 
         [0044]    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 . 
         [0045]    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  FIG. 1 . 
         [0046]    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. No. 6,860,979 B2 and U.S. Pat. No. 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&amp;W content of the stream  250  as it exits the electrostatic treater  70  is no greater than 0.5% BS&amp;W and 285 mg/l salt. 
         [0047]    Referring now to  FIG. 7 , another preferred embodiment of a topside process train  260  includes two high pressure separator/degassers  200  operating in parallel, with each separator/degasser  200  receiving approximately half of a mixed stream  15  containing 20 to 80% water and 80 to 20% oil, an intermediate pressure flash vessel  30  arranged downstream of the high pressure separator/degassers  200  that receives the combined outlet stream from the separator/degassers  200 , a compact electrostatic separator pre-treater  50  arranged downstream of the intermediate pressure flash vessel  30  that receives the outlet stream  210  from the intermediate pressure flash vessel  30 , a low pressure degasser  40  arranged downstream of the compact electrostatic separator pre-treater  50  that receives the outlet stream  270  from the pre-treater  50 , a crude oil storage tank (“cargo tank”)  60  arranged downstream of the low pressure degasser  40  that receives the outlet stream  280  from the low pressure degasser  40 , and, finally, an electrostatic treater  70  arranged downstream of the cargo tank  60  that receives the outlet stream  290  from the cargo tank  60 . 
         [0048]    The equipment for each component of the process train in  FIG. 7  is the same as the equipment for the process train described in  FIG. 6  and Table 5, with the same advantages in reduced size and weight. Preferably, the BS&amp;W content of the stream  300  as it exits the process train  260  is no greater than 0.5% BS&amp;W and 285 mg/l salt. 
         [0049]    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.