几个句子

不同油田所产原油的组分，从来没有完全相同的。尽管所有石油基本上都是由若干碳氢化合物组成，但每个油层所含碳氢化合物的比例却有大小不等的差别。每个油层的油性都需要单独作出评价。油样要在化验室进行一系列的化验，其目的主要在于针对情况确定在提炼中所应采取的方法。

Petroleum is not normally used today in the crude state. The mixture of oils of which it is composed must be separated out into a number of products such as petrol, aviation spirit, kerosene, diesel oils and lubricants, all of which have special purposes. The main method of separation used in refineries is fractional distillation, although further processing is normally required to produce marketable petroleum products. The different hydrocarbons present in petroleum have different boiling temperatures, and the fractions can therefore be isolated according to their boiling temperatures. Petrol,for instance, is a mixture of the lower-boiling hydrocarbons, with boiling temperatures ranging from 1000C to 4000C . Diesel oils on the other hand have boiling temperatures of upwards of 4000C 现在人们一般不直接使用原油。组成石油的油质混合物必须分离成为一系列的石油制品：汽油、航空汽油、煤油、柴油以及润滑油。所有这些产品都有其特有的用途。炼油厂所使用的主要分离方法是分馏，不过分馏所得一般都需要一步加工才能成为可供销售的石油制品。石油中所含的各种碳氢化合物具有各不相同的沸点，因此可以根据沸点的不同将组分分离开。比方说，汽油就是一种由沸点较低的碳氢化合物组成的化合物，其沸点100℃-400℃，而柴油的沸点则在400℃以上。

petroleum is essentially a nonrenewable natural resource , an almost useless conglomerate(混合物混合物混合物混合物) comprised of very useful substances . It exists underground in liquid, solid , semisolid , and gaseous states . The name “petroleum” is derived from the Latin words petra and oleum , mean-ing“rock oil.”石油基本上是一种不可再生的自然资源，是一种几乎没有什么用处的混合物，但是组成石油的各种物质却非常有用。石油以液态，固态，半固态，气态的形式积存于地下。石油这个名称来源于拉丁语“petra”“岩石”和”oleum”“油”两个词，意思是“岩石油” Created only by nature but exploited by man , petroleum is a nonrenewable resource because people consume it approximately one million times faster than nature can create it . Timber is a renewable natural resource ; it can be harvested , replanted , then reharvested in a few decades . In a sense , petroleum ‘seeds” are being planted today because the natural processes that create pe-troleum occur continuously . However , the results cannot be harvested for many millions of years. The petroleum that man “harvests” today was “plarted”30-6000 million years ago! That is why petroleum is considered nonrenewable石油只能是由自然界生成，而由人开发利用。人类消耗石油的速度比自然界生成石油速度快100万倍，所以石油是一种不可再生的自然资源。树木是可再生的自然资源，树木可以砍代，再种植，几十所后又可以砍伐了，从某种意义上来说，现在正在播种石油的“种子”，因为生成石油的过程是连续发生的。然而其结果要过几千万年以后才可以收获。人们现在“收获”的石油是3000万年到60亿年前“种值”的，这就是为什么说石油被认为是不可再生的原因。

Petroleum is composed of various complex combinations of hydrogen and carronatorns .these combinations are called Hydrocarbons . Hydrocarbons are immisble(不可容混的不可容混的不可容混的不可容混的) in wa-ter ; that is , the hydrocarbons will not readily mix with water . Often the hydrocarbons foune in nature are not pure substances . They may have other elements and compounds assonted with them , such as sulfur , carbon dioxide , water , and nitrogen 石油是由氢原子和碳原子的各种复杂的化合物组成的。这些化合物叫做“碳氢化合物”。碳氢化合物不溶于水，即碳氢化合物与它掺杂在一起，像硫，二氧化碳，水的氮。