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Proceedings Papers

Paper presented at the Southeast Asia Show, February 21–24, 1984
Paper Number: SPE-12429-MS
... pressure, multiple flaw path swivel to conduct fluids between the weathervaning vessel and the non-rotating buoy or riser. In August 1981, a facility went into operation using this new high-pressure, multiple flow path swivel producing from the subsea-completed wells in the Philippines. More recently...
Proceedings Papers

Paper presented at the Southeast Asia Show, February 21–24, 1984
Paper Number: SPE-12434-MS
... the expenditure of swivels. The immense influen- ce of the heod weight on the overall colunm structure design should not be disregarded. The unijoint alternative we would prefer has been described already. The a~efi~onmen~ m the combination of crude oil pipe and unijoint creates the necessity to exchange...
Proceedings Papers

Paper presented at the Southeast Asia Show, February 21–24, 1984
Paper Number: SPE-12430-MS
... <nowiedge of Reservoir 3ehaviour ?rior to Full Development CURRENT INSTALLATIONS 3efore looking at the number of current installations, it is necessary to define the meaning of a floating production facility as used in this survey. Firstly, to aualify, the facilitv must have the capability ta process an oi~/qas/~ater system. This excludes facilities such as a storage only sys- tems floatinta water treatment baraes, offshare L?G storage plant, etc. Secondly, the primary shaoe and function of the supporting structure must be designed to float which obviously includes ships such as tankers, semi- submersible and barges. The tension leg platform is included in this discus- sion although there are no installations operatina at this date. Also in- cluded is the jack-up as it carries with it many of the floating cancepts required for ria mabilitv. The installations of floating production facilities are relatively new to the industry. The first jack-up was in use in 1971 in the Ekofisk Field in the North Sea. The first semi-submersible installation was started up in June 1975 in the Arayll Field, also in the North Sea. The first tanker based floating production system was commissioned in the Castellon Field Offshore, Spain. Considering that the affshare industry started in earnest with Gulf of Mexico developments in the 1940 s, it is perhaos surprising that the floatina system has been so lang in development. Figure 5 illustrates the progression of the tatal number af floating systems since 1971. 1s71 lslg 1- lm FIGURE 5: FLOATING PRODUCTION FACILITY INSTALLATIONS 11-24 Jack-Uo Rigs Table 1 shows that there have been only four iackups that have been used in pr~duction service and two of these are no lonaer operating. The orablems af depth limitations, low topside deckload capacity and dependence on subsea .? A hmS011 cunu*b*ui,S,IIUrndthe use of jack-ups. TABLE 1: JACK-UP BASED PRODUCTION INSTALLATIONS 1 Dcte On Depth No. Of Rate Field ODerator Location Stream (m) Wells (m BPD) Rig I Ekofisk Phillips North Sea 1971 70 - 40 Gulftide Enchova Penrod Leste 1 Petrobras Brazil 1979 80 3 10 72 Badejo Petrobras Brazil 1981 85 4 10 Penrod 72 Ivory Es~oir Phillips Coast 1982 87 5 20 Dan Duke Semi-Submersibles Table 2 shows a total count of 9 semi-submersibles converted to production service, and used in 11 different fields. The trend for converted semi- submersibles was started in the North Sea with the Argyll Field installation -.in June l~la, a trend that wi~~ tAmiia~~gh~ I-IPt~ the installation of the purpose built Balmaral semi-submersible in 1985. TABLE 2: SEMI-SUBMERSI13LE BASED PRODUCTION INSTALLATIONS Field Operator Location Date On Depth No. of Rate Stream (M) Wells (MBPD) Vessel Argvll Hamilton North Sea 1975 75 40 Transworld 58 Enchova . Petrobras Brazil, 1977 130 1 10 Sedco 135-D Dorado Eniepsa Spain 1977 95 3 10 Sedco 135 Buchan BP North Sea 1980 115 8 75 Pentagone 83 Pampoi Petrabras Brazil 1980 120 1 10 Sedco 135-D Casablanca Chevron Spain 1980 160 2 10 Afortunada Linguado Petrobras Brazil 1981 100 3 20 Transworld 61 Bicudo Petrobras Brazil 1982 i30 4 20 C-.A A4WUW Bonito ?etrobras Brazil 1982 zoo 12 30 Penrod 71 Garoupinha Petrobras Brazil 1982 120 5 10 Sedco 135-F ~u~ ~~ Pampo Petrobras Brazil 1983 5 20 Stafla =ven though the semi-submersible production facility got its start in the iNorth Sea, the Brazilian National Oil Company, Petrobras, has token the areatest advantage of the concept. ?etrobras commissioned a converted Sedco- 1350 semi-submersible in the Enchova Field in August 1977. It produced 8.6 million barrels at Enchova unril it was decommissioned in Juiy 1980. The same vessel was then moved to the Pampo Field in December 1980 and produced 2.2 miilion barrels until October 1981. It was again moved to Petrabras 3icudo Field where it started production in January 1982 and is still pro- ducing. This one case alone stranqly illustrates the flexibility and mobi- lity af the floating production system. -Shio-Shaoe (Tankers) Table 3 indicates that there have been six tankers that have been converted to productionlstoraae service, five of which are still oaerating. The con- cept was started in August 1977 when Shell started uo its Castellon Field, Offshore Spain. The depth record for a floating Production tanker is held by Exxon in its Hondo Development in 160 meters of water, offshore Southern 1--1:x n-- _x LL_ 1, 2L L, uu*AiurrlLu. urle or me primary ~zmlzazzons of lfoating facilities particular and in ship-shape structure is the number of wells serviceable through the high pressure swivels. The recently comnissianed Tazerka Field operated by Shell now incorporates a record six individual flow paths although cur- rently only four are required. lhe table also shows a definite trend to larger tankers culminating in the conversion of a 210,000 DWT tanker for the Tazerka Field. TABLE 3: TANKER BASED PRODUCTION INSTALLATIONS Date No. Field Operator Location On Denth of Rate Tanker Name Stream (m) Wells (mBPD) (mDWT) Castellon Shell Spain 1977 117 3 20 60 Goroupa Petrobras Br~zi~ 1979 I3Q 7 ~~ ~~ Nilde AGIP Italy 1980 90 1 85 Hando Exxon California 1981 160 - 50 50 Cadlao Anoco Philippines 1981 90 2 30 125 Tazerka Shell Tunisia 1982 140 4 30 210 COMPARISONS We have looked at the reasons why an operator would choose a floating production system, where they have been utiiized in the past; now we shOttid consider what tyDe of flaa+ng svstem. Any analysis of the optimum production system for a given field is a lengthv, detailed exercise, but it is useful to look at broad topics that consider the advantages and disadvantages of the different aporaaches. Figure 6 illustrates the advantages and disadvantages of a shin-shape (tan- ker) tyoe production facility. Prabably the single biagest advantage is its ability to stare product. This feature builds into the system a high degree of operational efficiency combined with the lowest oossible cost o+ export. 11-26 SPE12436 Without this feature the production system would need an exoort oipeline to shore (rarely ~conomicallv feasible in a marginal field) or a freauent shutdown for the chanae of a transit tanker. There is also a cost savina in not having a transit tanker idle at the production location during production process. FIGURE 6: TANKER FEATURES the 8 * * * * Advantages Low Conversion Cost l Product Storage Capability * Short Conversion Schedule * Larae Deck Space/Caoacity Side BY Side Offloading Disadvantages Sensitive To Environment Weathervaning No Drilling/Workover Capability Tankers are relatively inexpensive to acquire and convert to floating pro- duction facilities, especially considering today s surplus of VLCC tankers. It has been estimated that the cost to acquire and convert a 120,000 dwt tanker is of the order of 20 million (US BY the very nature of their design, tankers have a large, uncluttered deck space that is ideal for the addition of processing facilities. c~u modifications to the deck are not burdensome due to the ability to spread t .41 the equ&Pllwnk-u-v-v ~fetv systems on the tanker are usually compati- ble because the ships are already designed to handle volatile products. The schedule, from time of project approval to first oil processed, can be very short. The tanker based system for the Shell Castellon Field was in operation 11 months after project go ahead was obtained. me tanker based production system also has its drawbacks. The one meriting the most attention is its performance in high sea state conditions. Due to ~~s sha,pe, a tanker cannot attain the stable motion characteristics of a semi-submersible in high sea state conditions. Hence we see the pre6Gfide- rance of converted tankers in the milder condition of South East Asia, Offshore California and the Mediterranean (maximum significant wove height of about 10 meters), but no installations in areas such as the North Sea (maximum significant wave heiaht of about 15 meters). There has been much investigation in this area to expand the role nf tanker hase~ facilities to rouahnr environments1 conditions. Marathon has invwtiaated the use of a productionlstorage tanker in the North Sea and found it to be feasible. Shell has recently installed a floating storage svsternonlv in its Fulmar Field in the North Sea. The system consists of a 210,000 dwt tanker moored A. .-A A A for ~ 25 ~ter wave height.in Yu meters of vifitarUIIU-sew A second oroblem with this type of svstem is the need for weathervaning. The tanker must be allowed to weathervane with wind, - .- .-tt--nn+t= rnini-Wobe Ultub ,s mize the ~arces on the mooring and the tankers motian characteristics. In so A*;mm ~S necessarv to incorporate a swivel between the tanker and its mooring equioment. The swivel becomes the weok link in the system and re- auires significant attention. Past limitations in swivel desimn have limited the number of wells, the ooerating oressures and the flow rates for a ~rodu~ti~n sY~tern= In oddition, it has prevented the use of hi~h pressure 11-?7 water and gas reinfection systems. Significant progress has been made over the past few years with the commissioning of Shell Tazerka Field in 1982. This system incorporates a manifold between the wellheads and the swivel, allowing the inclusion of six J-inch independent flow paths, The final limitation of a tanker based system is that it is not feasible to incorporate drilling or workaver facilities without a major modification to the vessel itself, and is further complicated by the requirement to hold a fixed position (i.e. no weathervaning) over a well location during drilling operations. Figure 7 illustrates the aavantcges and disadvantages of a semi-submersible based production facility. FIGURE 7: SEMI-SUBMERSIBLE FEATURES * * l * Advantages Superior Mation Characteristics * Catenary Mooring (Na Weathervaning) l Drilling/Workover Capability * Surplus Available For Conversion * Disadvantages Low Payload Minimal Praduct Storage Capacity Relatively Expensive Longer Schedule The ~rimary arivantaqeis the semi s well known suoerior performance in harsh environmental conditions. The semi concept was originally developed to meet tbe AA= -~ -A AJ--A114- --ad ,8abA#m=aat=uu~8=u WW8~MiyuityVpCIULAWII ifi deep, hostile waters. l%is inherent steadiness makes it superior for ~erformance as a production facility. ,A,Rc~~ermA.,mrI+mm.m A4 e==r,~ Blb y= v -al s 1 1 A :-1 wauALJ.1*~ 1 I WII1 Al.= UAL.UAAUIIL =L=UUJIIC ~> its ability to be moored with a standard catenary system with no requirement for weathervaning. Elimination of weathervaning obviates the need far fluid swivels and greatly increases the flexibility of the system to deal with multiple wells ond higher pressures. The open area moon pool design...
Proceedings Papers

Paper presented at the Offshore South East Asia Show, February 9–12, 1982
Paper Number: SPE-10476-MS
... environments such as the North Sea. The principle common to all Single Point Moorings (SPM) in use today is that a shuttle tanker is moored to a permanent buoy by a braided synthetic rope or ropes as its bow. From a seabed pipeline, the product is discharged through a riser pipe or hose to a swivel assembly...
Proceedings Papers

Paper presented at the Offshore South East Asia Show, February 9–12, 1982
Paper Number: SPE-10477-MS
... the sub- marine and floating hoses and the buoyancy tanks. Two underbuoy hoses and all but one of the floating hoses were retained for future use. No scour was evident around mooring base and PLEM, the universal joints and the chain swivel were in good condition. the fluid swivel showed no leaks...

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