The constant attacks on Iraqis oil production facilities are not all the result of al Qaeda or Sunni Arab attempts to weaken the government, and take over. Most of the attacks are by criminals, and many of these are not attacks, but theft. Puncturing a pipeline to steal oil is a common "attack." There are some deliberate attacks to shut down the oil industry, and these are carried out by terrorists. But even some of these operations have criminal, rather than just political, intent. By disrupting the supply of petroleum products to the Iraqi people, the criminal gangs running the black market for fuel can quickly make a lot of money. If you time the "shortages" just right, you can maximize your black market profits.
Some 90 percent of the attacks on the oil industry are against the pipelines. These attacks have cost the government some $20 billion is lost sales, security and repair costs. The Sunni Arab groups trying to take over the government are behind the oil industry attacks, and about 40 percent of the money made from oil theft goes to pay for the terror campaign against the government. There are signs that this percentage is declining, as the thieves show a preference for staying alive to spend the oil theft proceeds. Attacking American and Iraqi troops is a high risk proposition, even if most of the activity is making and planting roadside bombs.
The solution is to return to the Saddam era approach to oil industry security. Saddam had a lot of the same problem with the black market and sabotage. Back then, the saboteurs were Kurds and Shia Arabs. Saddam's solution was massive security on the oil facilities. And that's what the current government is going for. Democracy did not bring an end to the criminal gangs and groups (now the Sunni Arabs) who believe that, if they can't have the oil, then no one can.