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1、阅读原文：Petroleum,consistingofcrudeoilandnaturalgas,seemstooriginatefromorganicmatterinmarinesediment.Microscopicorganismssettletotheseafloorandaccumulateinmarinemud.Theorganicmattermaypartiallydecompose,usingupthedissolvedoxygeninthesediment.Assoonastheoxygenisgone,decaystopsandtheremainingorganicmatt
2、erispreserved.石油是由原油和天然气组成，似乎都源自于海洋的有机物沉淀。微小的有机物沉积到海底并堆聚在海泥里，有机物会局部分解，消耗沉淀里的溶解氧，当氧气消耗殆尽分解便停止，留下剩余的有机物。Continuedsedimentation—theprocessofdeposits’settlingontheseabottom—buriestheorganicmatterandsubjectsittohighertemperaturesandpressures,whichconverttheorganicmattertooilandgas.Asmuddysedimentsarepres
3、sedtogether,thegasandsmalldropletsofoilmaybesqueezedoutofthemudandmaymoveintosandylayersnearby.Overlongperiodsoftime(millionsofyears),accumulationsofgasandoilcancollectinthesandylayers.Bothoilandgasarelessdensethanwater,sotheygenerallytendtoriseupwardthroughwater-saturatedrockandsediment.持续的沉积——堆积物沉
4、积到海底的过程将有机物埋在海底使之受到海底温度、高压的影响，最终转变成石油和天然气。当泥状沉积物被挤压在一起时，天然气和石油液滴会被挤出泥层，然后进入附近的沙层。经过很长的一个周期（数百万年），积聚的天然气和石油会在沙层中聚集。因为石油和天然气的密度都比水低，所以他们通常通过饱含水的岩层和沉积物往上升。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.油床是宝贵的地下石油积聚处，而油田是被一个或多个油藏覆盖区域。当人们发现油藏或油田时，就会把井钻到地下。固定的塔称为井架，建造井架是为了控制长距离的钻杆。现代使用的便携式钻井机安装使用
