sure, you can build 10 pipelines and OPEC still controls the price of oil.
OPEC does not control the price of oil. They are important and influence it but they certainly don't control it. If they controlled it, they would peg the price of oil that maximized their income and it wouldn't fluctuate much.
Why don't they control it? Because almost all the OPEC nations produce above their quota, at least those who can produce above their quota. OPEC produces 35%-40% of oil production. The only country that really has any influence over oil is Saudi Arabia, which produces about 15% of global production, and their influence is waning.
The price of oil isn't falling because of OPEC. The price of oil is falling because their is a lot of supply in the world. The collapse in oil over the past few days has been psychological. The mentioned OPEC - read Saudi - cuts were 300,000 to 500,000 barrels of oil a day, which wouldn't have made much of a dent in supply.