A common well-intervention operation involving a wide variety of mechanical scale-inhibitor treatments and chemical options. Mechanical removal is done by means of a pig or by abrasive jetting that cuts scale but leaves the tubing untouched. Scale-inhibition treatments involve squeezing a chemical inhibitor into a water-producing zone for subsequent commingling with produced fluids, preventing further scale precipitation. Chemical removal is performed with different solvents according to the type of scale:

路 Carbonate scales such as calcium carbonate or calcite (CaCO₃) can be readily dissolved with hydrochloric acid (HCl) at temperatures less than 250^oF (121^oC).
路 Sulfate scales such as gypsum (CaSO₄路2H₂O) or anhydrite (CaSO₄) can be readily dissolved using ethylenediamine tetraacetic acid (EDTA). The dissolution of barytine (BaSO₄) or strontianite (SrSO₄) is much more difficult.
路 Chloride scales such as sodium chloride (NaCl) are easily dissolved with fresh water or weak acidic solutions, including HCl or acetic acid.
路 Iron scales such as iron sulfide (FeS) or iron oxide (Fe₂O₃) can be dissolved using HCl with sequestering or reducing agents to avoid precipitation of by-products, for example iron hydroxides and elemental sulfur.
路 Silica scales such as crystallized deposits of chalcedony or amorphous opal normally associated with steamflood projects can be dissolved with hydrofluoric acid (HF).