When the oil-producing rate of an oil well declines, a workover job is performed to increase production. The workover may include bailing out accumulated scale and other solids, acidizing, fracturing, use of paraffin solvents,
When the oil-producing rate of an oil well declines, a workover job is performed to increase production. The workover may include bailing out accumulated scale and other solids, acidizing, fracturing, use of paraffin solvents, or scale solvents, and the like. Removal of calcium sulfate scale from wells has presented problems, particularly when the scale is in a massive, dense, impermeable form, or when the scale is deposited in pores and other openings within the formation.
In removing scale from surface equipment, the solvent can be heated, circulated, filtered, and analyzed to determine whether it is spent. Further the amount of scale and thus the minimum amount of solvent needed can be estimated. In a well, most of these manipulations are difficult or impossible. In addition, the amount, nature, and location of the scale in surface equipment can usually be rather accurately determined. In a well, on the other hand, the cause of the reduced oil-producing ability is frequently unknown. Not only are the amount, nature, and location of the scale uncertain, but sometimes it is not even known whether scale is present at all. On the surface, where conditions