Can we stop the oil spill in Gulf of Mexico?

Eventually yes. Next week, maybe not.

There has never been a well that could not be eventually capped. This is done in two steps, a) bringing the well under control (no more flow) and b) placing a permanent plug (usually cement) in the hold.

The conventional means of killing an offshore blowout well is with drilling relief wells. Usually one well is drilled, but in this case two wells are being drilled. Completion is estimated to be late July.

BP has tried to actuate the blowout preventers using their ROV's. This failed. The "top kill" is an unconventional means of killing the well, and it is being attempted to reduce the time that the well will be spilling oil. The outcome of this attempt as of today (May 28) is unknown.

There is a several other options being considered if the top kill is a failure. One is to place a second blow out preventer on top of the existing well. The well can be shut off using a valve. It is unconventional, particularly performing this at 5,000 ft.

There can always be technical problems in drilling and completing relief wells, so it could be later than late in July. But, most industry experts agree that eventually the conventional approach will succeed. There's a slight chance that technical problems could delay the completion into August or September.

One reason for the success, is the wellbore will penetrate the same formation as the first well, so the driller will have a much better knowledge of the formation's properties. A second reason to be optimistic is there is a ready supply of materials in the gulf coast for any contingency.