Saudi Aramco, France's Air Liquide in nitrogen deal (well injection)

KHOBAR, Saudi Arabia May 21 (Reuters) - French industrial gases group Air Liquide (AIRP.PA: Quote) signed on Saturday a long-term agreement to supply nitrogen to state oil giant Saudi Aramco .

Under the 20-year deal, the French firm will supply at least 5 million standard cubic feet per day of nitrogen to support sea water injection in Aramco's oilfields, officials from Aramco and Air Liquide said during a signing ceremony.

It would also supply liquid nitrogen to Saudi Aramco facilities.

Nitrogen removes oxygen from sea water which is injected into the reservoir to maintain the well potential.

The value of the agreement was not disclosed and no details were provided as to which oilfields would be targeted.

http://af.reuters.com/article/energyOilNews/idAFLDE74K06O20110521

I wonder how it does that? I need to research it. Because if it means N2 replaces O2 and adds nitrogen to seawater, that is not good. Or possibly it is just a temporary addition to the well water, and eventually returns to the atmosphere from where it was originally taken?

(I once visited France's Air Liquide in Paris for tech courses as an employee of one of its subsidiaries.)

Found this:
Deoxygenation of seawater has been demonstrated as an environmentally friendly ballast water
treatment to control introduction of non-native aquatic species.1 Investigators have proposed that the
same treatment provides a low-cost, effective corrosion control measure for uncoated carbon steel
ballast tanks based on the concept that reducing oxygen from the ballast tanks will limit oxidation.1, 2
Matsuda et al.2 conducted shipboard trials by sealing a ballast tank at the deck and installing vertical
pipes into the headspace. They reported that pumping pure nitrogen gas into the headspace for 1.5 hr
reduced dissolved oxygen (DO) levels in the seawater to approximately 0.2 parts-per-million (ppm) and
decreased the rate of uniform corrosion of carbon steel by 90% as determined by weight loss.
https://www.corrdefense.org/Academia%20Government%20and%20Industry/06T072.pdf