Be consistent in your choice of voice. A shift in voice without reason will confuse your reader. For example, do not combine a passive voice clause with an active voice clause in the same sentence. See also Lack of Parallelism.
The researchers will drill a succession of holes in the
seafloor and thin pipes will be extended through which the
researchers will lower equipment for sending sound waves through the rock and
hydrate deposits.
The researchers will drill a succession of holes in the
seafloor and they will extend thin pipes through which they
will lower equipment for sending sound waves through the rock and hydrate
deposits.
--David Graham, "Harvesting Natural Gas from the Ocean Floor," Technology Review