Surfactant/foam enhanced aquifer contacting and modeling for aquifer remediation
Miller, Clarence A.; Hirasaki, George J.
Doctor of Philosophy
Experiments and numerical simulations were carried out to improve the understanding of foam flow in underground porous media, especially three-dimensional foam flow, and to develop a numerical model for the design of the foam hydrogen sparging process for aquifer remediation. Injection of hydrogen is a promising method to enhance in situ anaerobic biodegradation of chlorinated solvents. The use of foam formed in situ by injection of hydrogen and a suitable surfactant solution greatly extends the horizontal migration of hydrogen in the subsurface, especially near the bottom of the aquifer where chlorinated solvents normally reside. The number of hydrogen injection wells required is thereby reduced. Experiments were conducted in a 2x2x2 foot glass tank filled with sand and instrumented to permit sampling or measurement of local pressure differences as a function of time at 36 points located at 9 lateral positions and four elevations. After the tank was filled with surfactant solution, gas was injected at constant pressure from one corner near the bottom of the tank. In some experiments the packing of the sand was homogeneous; in others it was layered. The experiments confirmed that foam greatly increases lateral gas distribution along the bottom as well as average gas saturation in the tank. A model was developed to simulate three-dimensional foam flow in porous media and was incorporated into the existing reservoir simulator UTCHEM. The model changes the gas relative permeability curve and gas viscosity from those of ordinary two-phase flow to represent the reduced gas mobility when foam is present. All except one parameter of the model can be obtained from foam experiments in one-dimensional sand columns. This parameter is a geometric factor, which accounts for the greater mobility of foam in three dimensions than in one dimension for similar conditions, presumably the result of the greater number of possible flow paths in three dimensions. A history match of several of the above tank experiments showed that if foam mobility in the tank was taken to be about five times greater than in a column, simulated average gas saturation, gas injection rate, gas distribution and pressure profile six inches above the bottom of the tank were in good agreement with experimental results for the homogeneous packing. For the layered packing it was also necessary to fit another parameter to the data to account for generation of additional foam by flow, of gas from lower to higher permeability regions. The simulator was used to design a foam hydrogen sparging process for a hypothetical aquifer. Results showed that with foam well spacing could be increased by 80% for a particular homogeneous aquifer while maintaining about the same sweep efficiency near the bottom of the aquifer.
Chemical engineering; Petroleum engineering