Characterization of amorphous aluminosilicates is best accomplished using an integrated approach involving polarized light microscopy, X-ray diffraction, and SEM-EDS analyses. The amorphous scales discussed in this study are from the near wellbore area and consist primarily of SiO2 and Al2O3 with minor Na2O and H2O. Their refractive index ranges from 1.49 to 1.51, and at least one broad X-ray diffraction "hump", ranging from d = 3.1 Å to 3.5 Å is always present. Field results and laboratory studies indicate that effective removal of these deposits generally requires the use of a combination acid treatment. The use of an organic acid preflush (10% acetic) followed by hydrochloric-hydrofluoric (12%-3%) acid has been particularly successful. In addition, metal chelating agents (e.g., nitrilotriacetic and citric acids) should be incorporated in all acid treating systems to prevent aluminum-rich amorphous phases from reprecipitating.

Keywords:
reaction, acidizing, drilling fluid chemistry, amorphous substance, silicate, aluminosilicate scale, solubility, noncrystalline material, upstream oil & gas, scale deposit
Subjects:
Drilling Fluids and Materials, Reservoir Characterization, Information Management and Systems, Drilling fluid selection and formulation (chemistry, properties), Acidizing, Exploration, development, structural geology, Well Operations, Optimization and Stimulation
Copyright 1992, Society of Petroleum Engineers
You can access this article if you purchase or spend a download.