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1、閱讀原文：Petroleum,consistingofcrudeoilandnaturalgas,seemstooriginatefromorganicmatterinmarinesediment.Microscopicorganismssettletotheseafloorandaccumulateinmarinemud.Theorganicmattermaypartiallydecompose,usingupthedissolvedoxygeninthesediment.Assoonastheoxygenisgone,decaystopsandtheremainingorganicmatt
2、erispreserved.石油是由原油和天然氣組成，似乎都源自于海洋的有機物沉淀。微小的有機物沉積到海底并堆聚在海泥里，有機物會局部分解，消耗沉淀里的溶解氧，當(dāng)氧氣消耗殆盡分解便停止，留下剩余的有機物。Continuedsedimentation—theprocessofdeposits’settlingontheseabottom—buriestheorganicmatterandsubjectsittohighertemperaturesandpressures,whichconverttheorganicmattertooilandgas.Asmuddysedimentsarepres
3、sedtogether,thegasandsmalldropletsofoilmaybesqueezedoutofthemudandmaymoveintosandylayersnearby.Overlongperiodsoftime(millionsofyears),accumulationsofgasandoilcancollectinthesandylayers.Bothoilandgasarelessdensethanwater,sotheygenerallytendtoriseupwardthroughwater-saturatedrockandsediment.持續(xù)的沉積——堆積物沉
4、積到海底的過程將有機物埋在海底使之受到海底溫度、高壓的影響，最終轉(zhuǎn)變成石油和天然氣。當(dāng)泥狀沉積物被擠壓在一起時，天然氣和石油液滴會被擠出泥層，然后進入附近的沙層。經(jīng)過很長的一個周期（數(shù)百萬年），積聚的天然氣和石油會在沙層中聚集。因為石油和天然氣的密度都比水低，所以他們通常通過飽含水的巖層和沉積物往上升。Oilpoolsarevaluableundergroundaccumulationsofoil,andoilfieldsareregionsunderlainbyoneormoreoilpools.Whenanoilpoolorfieldhasbeendiscovered,wellsaredr
5、illedintotheground.Permanenttowers,calledderricks,usedtobebuilttohandlethelongsectionsofdrillingpipe.Nowportabledrillingmachinesaresetupandarethendismantledandremoved.Whenthewellreachesapool,oilusuallyrisesupthewellbecauseofitsdensitydifferencewithwaterbeneathitorbecauseofthepressureofexpandinggastr
6、appedaboveit.Althoughthisriseofoilisalmostalwayscarefullycontrolledtoday,spoutsofoil,orgushers,werecommoninthepast.Gaspressuregraduallydiesout,andoilispumpedfromthewell.Waterorsteammaybepumpeddownadjacentwellstohelppushtheoilout.Atarefinery,thecrudeoilfromundergroundisseparatedintonaturalgas,gasolin
7、e,kerosene,andvariousoils.Petrochemicalssuchasdyes,fertilizer,andplasticarealsomanufacturedfromthepetroleum.油床是寶貴的地下石油積聚處，而油田是被一個或多個油藏覆蓋區(qū)域。當(dāng)人們發(fā)現(xiàn)油藏或油田時，就會把井鉆到地下。固定的塔稱為井架，建造井架是為了控制長距離的鉆桿。現(xiàn)代使用的便攜式鉆井機安裝使用
