H. Scott Fogler
Ame & Catherine Vennema Professor of Chemical Engineering
and the Arthur F. Thurnau Professor
The University of Michigan
Ann Arbor, Michigan 48109-2136

A Novel Application of Chemical Reaction Engineering
to the Petroleum Industry

Acidization is the process of injecting acid mixtures down an oil well out into the reservoir to dissolve the porous media. This dissolution generates an increase in porosity and permeability thereby allowing the oil in the reservoir to flow out at a greater rate. Unfortunately, there have been cases in the Gulf of Mexico where significant decreases in permeability have been observed. The unique feature about the Gulf of Mexico is that many reservoirs contain the zeolite analcime, which dissolves in hydrochloric acid to form monosilicic acid and oligomers. These oligomers polymerize and coalesce to form spherical silica particles, which subsequently block the pores and damage the reservoir formation.

Fundamental studies were undertaken on kinetics of silica particle formation and growth. Particle sizes measured as a function of time by dynamic light scattering revealed that the particles grow exponentially and that higher HCl concentrations result in a much faster rate of monosilicic acid disappearance as well as faster particle growth rates. Furthermore, the monosilicic acid disappearance and silica particle growth were studied in solutions of 4M HCl plus 1M of different salts. The monomer disappearance rates and particle growth rates increased in the order AlCl₃ > CaCl₂ > MgCl₂ > NaCl > pure HCl.