【经济学人】深入地底探索DNA新用途丨2017.03.16丨总第844期

• Prospect for： 勘探

• Shale： n. 页岩；泥板岩

• Drill：vt. 钻孔

To acquire such knowledge, drillers often use tracers . These are materials that can be injected into the ground in small amounts at one point and then detected reliably if they turn up in other places—thus showing that those places have subterranean links to the point of injection. The supply of decent tracers, however, is limited. About 100, mostly dyes or mildly radioactive materials, are in routine use. This constrains the number of possible injection points in a particular area, and thus the amount of tracking that can actually be done. Yet in many cases—for example, a long well that runs horizontally through a particular rocky stratum —more than 100 injection points might ideally be required. The numerical constraint on tracers extends, moreover, into time, as well as space, for injecting one poisons the well, as it were , thus confusing future attempts to employ the same agent.

为获取此类信息，钻探人员通常会使用示踪剂：将少量示踪剂在某一地点注入地下，然后检测示踪剂是否在其他地点出现。如果是，则说明这些地点与注入点存在地下连接。但是，想要找到一种良好的示踪剂十分困难。目前能够常规使用的示踪剂有大约100种，其中大部分都是染色材料或者具有轻微放射性。这就限制了特定区域可注入点的数量以及实际的可追踪量。而且在大多数情况下，注入点的数量都很多。举例来说，一个很长的探井沿特定岩层水平延伸，那么其需要的理想注入点会超过100个。此外，示踪剂的数量限制随着时间推移（以及空间的变化）变得越发严重，而且由于曾经发生过注入示踪剂导致探井遭到污染的事件，未来是否应该继续使用相同指示剂也存在争议。

• Tracer： n. 示踪物；追踪者；描图者；绘图工具

• Subterranean： adj. 地下的；秘密的；隐蔽的

• Stratum： n. （组织的）层；地层；社会阶层

• as it were：可以说是，似乎就是；好像

The problem would go away, though, if a tracer could be found that was essentially the same with every use, and would thus behave in a predictable way, but was different in detail on each occasion, so that both the time and the place of its injection could be known reliably when it turned up elsewhere. And such a substance exists. It is called DNA. The four types of chemical “letter” of which this molecule is composed can be written in any order you like, giving infinite variety to individual batches of the stuff. Unfortunately, DNA is a delicate molecule, ill-equipped to survive the extreme temperatures and stresses found inside boreholes . Attempts in the 1990s, by Statoil, Norway’s state-owned fossil-fuel company, to use it as a tracer failed. But technology has moved on, and others are now trying again.

不过，如果能够找到一种理想的示踪剂，问题就迎刃而解了：它应当不会因多次使用而发生变化，既可预测又在每次使用时有着细节上的不同，无论在何处出现都能确切地知晓其注入时间和地点。这种物质其实是存在的，它就是DNA。DNA分子由四种脱氧核苷酸组成，这四种组分可按照任意顺序排列，其组合方式无穷无尽。不幸的是，DNA过于脆弱，适应性不强，无法适应钻井中的极端温度和压力。早在二十世纪九十年代，挪威的国有化石燃料企业Statoil就试图利用DNA作为示踪剂，不过未能成功。但随着科技的发展进步，人们又开始了新一轮的尝试。