Oil drilling....

is it damaging to earth? after taking millions of barrels of oil from the ground, seas ,etc ...does'nt that have an effect on earth? what happens to all that "space" created underground?

In depends entirely on the surrounding geology. With Oil I believe that drilling rigs often pump in a liquid to ease extraction of the oil. With gas coal and limestone I believe there are voids left.

As far as being concerned about them well for the most part they are a long way under the earths surface and are unlikely to cause you any problems unless you build a house without a "survey" on a sink hole and it subsequently falls in...

thank you