Particularly in oil production, as much or more water can be produced as the hydrocarbons themselves. This water is often referred to as formation water or produced water and contains many dissolved mineral ions such as sodium, calcium, barium, strontium, zinc, lead and iron to name a few. Because most of these waters are high in sodium and chloride, they are referred to as brines. When brines change temperature or pH or are mixed with other waters containing carbonates and sulfates, a variety of mineral precipitates or scales occur. Such common scales as calcium carbonate, calcium sulfate, barium sulfate and strontium sulfate regularly occur. These scales can become so severe that they will plug, reduce and eventually block production from the well.
Particularly troublesome is the quick formation of iron sulfide (FeS) scales. These hard scales become voluminous, buildup on equipment surfaces, promote underdeposit corrosion and plug wells and all associated field equipment, including treaters, separators pipes, evaporators and desalters. Sulfides are normally generated from the presence of hydrogen sulfide gas, either naturally from the formation, known as sour gas, or from indigenous bacteria spread throughout the well from the drilling process. This bacteria is referred to sulfate reducing bacteria and through their metabolic process convert sulfates into hydrogen sulfide gas. Acidizing treatments to dissolve sulfide and other scales may also create hydrogen sulfide gas further mitigating the process.