Because the land based wells require more digging, calculations for estimating the amount of oil in the oil well do not apply as well to them as they do to deep sea wellsThis sentence is absolutely correct as is. I think you may be getting confused with the
general practice that “repeated” occurrences of a pronoun tend to refer to the same antecedent. But notice here that THEY and THEM are not the same pronoun. They are two different pronouns. In fact if used in the same clause, these two SHOULD not refer to the same thing because of the way they are used. “They” is used in place of SUBJECT – i.e. the doer of the action. “THEM” is used in place of OBJECT – -i.e. the entity on which action is performed.Lets take a simple example:
Children like
chocolates to such an extent that
they can eat
them all day long.
As you see here “they” has to refer to “children” and “them” has to refer to “chocolates”. In fact if these two refer to the same thing then the sentence will be completely nonsensical – children can eat children…
Now lets come back to the sentence in question. We should always understand the meaning of the sentence to understand what pronouns should refer to.
Because the
land based wells require more digging,
calculations for estimating the amount of oil in the oil well do not apply as well to
them as
they do to deep sea wells
In this sentence, it is clear that the author is talking about application of calculations for estimating the amount of oil in the land based wells (referred to by THEM). And then while stating the comparison, he then states that these calculations (referred to by THEY) apply better to the deep sea wells. It is absolutely allowable for THEM and THEY to refer to different entities.
Lets take another example:
Because
electrons move at the speed of light,
Newton’s laws to calculate momentum do not apply as well to
them as
they do to slower bodies.
Lastly, check out this sentence from WSJ:
Frequent-flier miles are an asset, and
consumers who have
them ought to be able to use
them as
they want, not as
their airline wants. (
https://blogs.wsj.com/middleseat/2011/10 ... hink-again)
I hope this helps in your understanding. Also, in future please refrain from posting
e-GMAT content on other public forums. If you have any questions about our content, post them on our forum and we will address your query at the earliest possible (we strive to respond within 24 hours). For this very reason we have one forum dedicated to every concept file. We do not allow our content to be posted on public forums because it makes the content public, making it unfair for our students who pay for the course. A lot of our students enroll in our course to try a fresh set of questions and if these questions are posted on the public forums then it defeats the purpose.
I hope you understand this.
I look forward to addressing your queries on
e-GMAT forums
Regards,
Payal