海洋平臺結(jié)構(gòu)概述

1、海洋平臺結(jié)構(gòu)概述 鄧忠超,1.為什么我們需要海洋平臺?,當(dāng)今世界面臨著人口、資源和環(huán)境三大問題。隨著世界人口的增長和陸地資源因加速開采而日漸枯竭，海洋資源的開發(fā)、海洋環(huán)境的保護與利用已成為世界各國普遍關(guān)注的問題。,Early Last Century - Huntington Beach, California,Early Last Century - Summerland, California,Beginning of the

2、 Offshore Industry,Offshore Mobile Drilling Rigs,Offshore Production – Variety of Platform Types,Trend – Moving into Deeper Water,Trend – Moving into Deeper Water,里海地區(qū)阿塞拜疆（50%） 哈薩克斯坦和土庫曼斯坦（30%-40%）,北海地區(qū)（產(chǎn)量最多）,海灣地區(qū),非洲

3、,遠東地區(qū),巴西 1997年儲量達169億桶,墨西哥灣,2.海洋平臺需要具有哪些功能?,海洋平臺:,海洋平臺是在海洋上進行作業(yè)的場所。海洋石油鉆探與生產(chǎn)所需的平臺，主要分鉆井平臺和生產(chǎn)平臺兩大類。在鉆井平臺上設(shè)鉆井設(shè)備，在生產(chǎn)平臺上設(shè)采油設(shè)備。平臺與海底片口有立管相通。平臺是進行海上鉆井與采油作業(yè)的一種海洋工程結(jié)構(gòu)。海洋平臺一般都高出海面，能夠避免波浪的沖擊。型式有三邊形、四邊形或多邊形。上下兩層甲板或單層甲板面供安裝、儲存鉆井或

4、采油設(shè)備用。,1)按運動方式，可分為固定式與移動式兩大類,,3.海洋平臺的分類,2)按功能，海洋平臺的分類有鉆井平臺、生產(chǎn)平臺、生活平臺、儲油平臺、近海平臺等。,1、坐底式鉆井平臺 坐底式鉆井平臺是早期在淺水區(qū)域作業(yè)的一種移動式鉆井平臺。平臺分本體與下體，由若干立柱連接平臺本體與下體，平臺上設(shè)置鉆井設(shè)備、工作場所、儲藏與生活艙室等。鉆井前在下體中灌入壓載水使之沉底，下體在坐底時支承平臺的全部重量，而此時平臺本體仍需高出水面，不受

5、波浪沖擊。在移動時，將下體排水上浮，提供平臺所需的全部浮力。如屬自航者，動力裝置都安裝在下體中。坐底式的工作水深比較小，愈深則所需的立柱愈長，結(jié)構(gòu)愈重，而且立柱在拖航時升起太高，容易產(chǎn)生事故。由于坐底式平臺的工作水深不能調(diào)節(jié)，已日漸趨于淘汰。,鉆井平臺,單樁柱坐底式鉆井平臺,建造中的坐底式平臺,2、自升式鉆井平臺 自升式鉆井平臺是由一個上層平臺和數(shù)個能夠升降的樁腿所組成的海上平臺。這些可升降的柱腿能將平臺升到海面以上一定高度，支

6、撐整個平臺在海上進行鉆井作業(yè)。這種平臺既要滿足拖航移位時的浮性、穩(wěn)性方面的要求，又要滿足作業(yè)時著底穩(wěn)性和強度的要求，以及升降平臺和升降樁腿的要求。 由于自升式平臺可適用于不同海底土壤條件和較大的水深范圍，移位靈活方便，便于建造，因而得到了廣泛的應(yīng)用。目前，在海上移動式鉆井平臺中它仍占絕大多數(shù)。,3、半潛式鉆井平臺 半潛式鉆井平臺，又稱立柱穩(wěn)定式鉆井平臺。它是大部分浮體沉沒于水中的一種小水線面的移動式鉆井平臺，它從坐

7、底式鉆井平臺演變而來，由平臺本體、立柱和下體或浮箱組成。此外，在下體與下體、立柱與立柱、立柱與平臺本體之間還有一些支撐與斜撐連接，在下體問的連接支撐一般都設(shè)在下體的上方，這樣，當(dāng)平臺移位時，可使它位于水線之上，以減小阻力；平臺上設(shè)有鉆井機械設(shè)備、器材和生活艙室等，供鉆井工作用。平臺本體高出水面一定高度，以免波浪的沖擊。下體或浮箱提供主要浮力，沉沒于水下以減小波浪的擾動力。平臺本體與下體之間連接的立柱，具有小水線面的剖面，主柱與主柱之間相

8、隔適當(dāng)距離，以保證平臺的穩(wěn)性，所以又有立柱穩(wěn)定式之稱。,1、重力式采油平臺 它一般都足鋼筋混凝土結(jié)構(gòu)，作為采油、貯存和處理用的大型多用途平臺，它由底部的大貯油罐、單根或多根立柱、平臺甲板和組裝模塊等部分組成，規(guī)模較大的，可開采幾十口井，貯油十幾萬噸，平臺的總重量可高達數(shù)十萬噸。各類平臺，根據(jù)作業(yè)要求，配備相應(yīng)的采油，處理及生活等設(shè)施。,生產(chǎn)平臺,2、導(dǎo)管架式平臺 樁基式平臺用鋼樁固定于海底。鋼樁穿過導(dǎo)管打入海底

9、，并由若干根導(dǎo)管組合成導(dǎo)管架。導(dǎo)管架先在陸地預(yù)制好后，拖運到海上安裝就位，然后順著導(dǎo)管打樁，樁是打一節(jié)接一節(jié)的，最后在樁與導(dǎo)管之間的環(huán)形空隙里灌入水泥漿，使樁與導(dǎo)管連成一體固定于海底。這種施工方式，使步上工作量減少。平臺設(shè)于導(dǎo)管架的頂部，高于作業(yè)區(qū)的波高，具體高度須視當(dāng)?shù)氐暮r而定，一般大約高出4-5m，這樣可避免波浪的沖擊。樁基式平臺的整體結(jié)構(gòu)剛性大，適用于各種土質(zhì)，是目前最主要的固定式平臺。但其尺度、重量隨水深增加而急驟增加，所以在

10、深水中的經(jīng)濟性較差。,4、牽索塔式平臺 牽索塔式平臺是一瘦長的桁架結(jié)構(gòu)，其下端依靠重力基座坐落于海底或是依靠支柱加以支撐，其上端支承作業(yè)甲板。桁架的四周用鋼索、重塊、錨鏈和錨所組成的錨泊系統(tǒng)加以牽緊，使它能保持直立狀態(tài)。由于這種平臺是由錨泊系統(tǒng)牽緊的，它在小風(fēng)浪時僅發(fā)生微幅擺動；風(fēng)浪大時，由于桁架結(jié)構(gòu)擺動幅度大，會把重塊拉得離開海底，從而要吸收掉風(fēng)浪的一部分能量，因此平臺仍可維持在許可范圍內(nèi)擺動。這種平臺結(jié)構(gòu)簡單，構(gòu)件尺寸小

11、，故所受到的風(fēng)、浪、流的作用力也小。這種平臺能適用于300～600m水深的海域。但若水深超過600米，則由于要提高桁架的抗彎能力，建造時所耗用的材料會大大增加，經(jīng)濟上不一定合算。,Offshore Oil and Gas Exploration,Exploration – Reservoir engineeringDrillingProductionTransportationDistribution to market,Off

12、shore Production Systems,Trend - Floating Production Systems,The search for hydrocarbon resources moves the offshore industry into deepwaters and harsh environments where the traditional technologies were not able to tap

13、 into.There is a continuous drive to reduce the development cost by searching for cost efficient platform types.The future trend: (i) efficient platform for large deepwater fields; (ii) low cost mobile platform for mar

14、ginal fields.Technology development holds the key for successful deepwater hydrocarbon exploration.,Tension Leg Platform - Classical,Tension Leg Platform (TLP) consists of a floating structure held in place by vertical,

15、 tensioned tendons connected to the sea floor by pile-secured templates. Features: Heave natural period 3 – 4 secondsMinimal heave, roll and pitch motionsCompliant in horizontal directionPayload sensitive Water de

16、pth limited to 5,000 – 6,000 ftLarge well bay size Dry tree application,Tension Leg Platform – Single Column,Attractive Features: Single column for ease of constructionExtended column arms to keep the roll and pitch

17、 natural periods lowLess number of tendons Lower deck weight because of less pry squeeze loadDrawbacks:Well bay size limited Self floating not stableApplication limited to small topsides weight,Tension Leg Platform

18、 – MOSES,Attractive Features: Flat plate design for ease of constructionExtended column arms to keep the roll and pitch natural periods lowLower deck weight because of less pry squeeze load due to reduced column span

19、Riser connect at the same level as the tendons to minimize riser strokeDrawbacks:Well bay size reduced Self floating less stableApplication limited to small topsides weight,Tension Leg Platform – ETLP,Attractive Fea

20、tures: Flat plate design for ease of constructionExtended column arms to keep the roll and pitch natural periods lowLower deck weight because of less pry squeeze load due to reduced column spanDrawbacks:Well bay si

21、ze reduced Self floating less stableApplication limited to small topsides weight,SPAR - Classical,SPAR Platform (SPAR) consists of a large diameter single vertical cylinder anchored to the seabed using taut or caternar

22、y mooring lines.Features:Deep draft to minimize heave motionHeave natural period over 25 secondsMinimal heave motionsSolid ballast at keel for floating stabilityLess payload sensitive compared to TLPBuoyancy can r

23、iser supportWater depth up to 10,000 ftDry tree application,,SPAR - Truss,,Attractive Features: Lower structural weightLess current load Smaller mooring system if static load governsLess vortex induced motionDraw

24、backs:Shorter natural periods at the absence of trapped waterSlightly large wave frequency motions,SPAR - Cell,,Attractive Features: Ease of structural design and fabricationLess vortex induced motionDrawbacks:Lim

25、ited to smaller size,SPAR Design Focus,Minimize topsides payload – Any increase of topsides weight has to be compensated by increase of solid ballast to maintain floating stability.SPAR and riser buoyancy can interactio

26、n. SPAR installation including upending is critical and can govern the global structure design.Vortex induced motion and its impact to mooring system design.,Semi-submersible,Floating Production System (FPS) consists o

27、f a semi-submersible unit which is equipped with drilling and production equipment anchored in place with wire rope and chain, or can be dynamically positioned using rotating thrusters. Features:Deep draft to minimize

28、heave motionHeave natural period over 20 secondsLimited heave motionLess payload sensitive compared to TLPWater depth up to 10,000 ftWet tree application,FPSO – Internal Turret Moored,Floating Production, Storage &a

29、mp; Offloading System (FPSO) consists of a large tanker type vessel moored to the seafloor.  An FPSO is designed to process and store production from nearby subsea wells and to periodically offload the stored oil to

30、 a smaller shuttle tanker. Have storage and can operate remote from pipeline networkWeather vane to reduce env. loadsSmaller mooring sizeVersatile for all regionsTandem offloading,FPSO – External Turret Moored,

31、Attractive Features: Easy for conversionEasy for installation and inspectionEasy for weather-vaneIncreases effective water depth (for shallow waters)Drawbacks:Limitation on mooring loadsLimitation on number of

32、risersMooring/bow interferenceLarge vertical motion at turret,Dis-connectable Turret,FPSO – Spread Moored,Attractive Features: For benign or directional environments, e.g. WOA, Brazil.Lower mooring costsOffloading

33、via buoy Drawbacks:Design govern by near beam sea conditionsLarge mooring sizeRoll motion Green water impact,FPSO Design Focus,Select turret mooring concept and develop system configuration.Mooring/riser/hull desi

34、gn load interaction.Mooring and riser arrangement inside the turret as the space is limited with the turret.Riser design as the vertical motion of the FPSO at turret is relatively large.,Comparison of Platform Features

35、,Offshore Production - Semi-Submersibles,Offshore Production - Tension Leg Platforms,Offshore Production - SPARs,Offshore Production - FPSOs,TLP Transport - Marco Polo,TLP Transport - Brutus,TLP Transport - Morpeth,TLP I