Paraffin and asphaltenes often build up in the perforations of oil wells, clogging them and impeding the flow of oil. Just as the flow of water can become a mere trickle due to a clogged irrigation pipe, the same is true of oil. As you can imagine, a clogged oil well is far from efficient. In order to improve the oil well's production, operators use an intervention known as oil well stimulation.
Oil wells are often stimulated by pumping acid mixtures into the well to dissolve the clog. Another technique involves using coiled tubing to pump chemicals directly to the clogged area. Some oil wells can benefit from a procedure known as "lifting." This procedure is typically used when heavy fluids have accumulated at the bottom of the well. These heavy fluids tend to interfere with the flow of the oil or natural gas. In order to remove these heavy fluids, oil producers often inject chemicals into the well in an attempt to "lift" the heavy fluids out of it. They also sometimes use coil tubing to circulate nitrogen within the well.
If you're concerned about the use of chemicals and acids, their potential environmental effect, or how they might degrade the oil, a green oil well stimulation option is also available. According to E & B Green Solutions, its oil well stimulation product, Well Wake Up, is part of its G-Clean oil field product line. These products are fully biodegradable and manufactured from USA-grown, plant-based materials. E & B Green Solutions' Well Wake Up is highly concentrated and custom formulated based on what's fouling the oil well. The two-part product is activated on-site where it is diluted with water and applied. When the two components mix, they cause a reaction and begin cleaning the fouled oil well.
"Well stimulation", Wikipedia, http://en.wikipedia.org/wiki/Well_stimulation
"Oil Well Stimulation", E&B Green Solutions, http://www.ebgreensolutions.com/applications/well-stimulation