Nature, Origin, Treatment and Control of Well-Bore Scales in an Active Steamflood, Wilmington Field, California

Abstract

Abstract Three principal families of scale minerals occur in this field, carbonates, sulfates and silicates. The carbonate scale is calcite. It is chemically and mineralogically complex owing to variable substitution of Mg for Ca in the crystal lattice. Four varieties of calcite are differentiated on the basis of Mg:Ca ratios. The amount of Mg increases with decreasing temperature. Carbonate scale is precipitated at higher temperatures than sulfate and silicate scale. Ions that form the carbonate and sulfate scales originate from formation waters. Scales that result from interactions of hot fluid with the formation (silicates) are not volumetrically significant. Long-term prevention of scale precipitation should focus on chemical treatment of fluids and reduction of well bore temperature.