| Title | Change in Permeability of Porous Medium in Silica Scaling Experiment Under Different pH and Suspended Particle Concentration |
|---|---|
| Authors | Loren TUSARA, Ryuichi ITOI, Daisuke FUKUDA, and Yoshitaka KAWAHARA |
| Year | 2014 |
| Conference | Stanford Geothermal Workshop |
| Keywords | silica scaling, suspended particle, bentonite, permeability |
| Abstract | Geothermal fluid that is being reinjected back to the formation may contain traces of suspended particles in the fluidas it flows from production wells through the pipes to reinjection wells. Buildup of solid deposits on the pore spaces of the formation reduces the ease of flow of the geothermal fluid in the porous medium. In this study, bentonite, a common mud drilling material, was used as a suspended particle in the silica scaling experiment. Different concentrations of bentonite (0, 0.1 and 1ppm) in synthetic silica solution of 700ppm at 80oC under basic (pH8) and acidic (pH5.5) conditions were investigated to know how these factors affect the permeability distribution of the porous medium. Result shows that in basic solution, the effect of bentonite concentration, however in small concentrations, is significant. Experiment run with 1ppm bentonite concentration only lasted for less than a day before the experiment was terminated due to high pressure in the porous column. Lowering the pH of the solution with the same 1ppm bentonite concentration greatly improved the permeability distribution of the porous medium. It took five more days before the permeability of that with low pH dropped to almost the same amount with that of higher pH value. The suspended particles may have formed an aggregate with the monomeric silica producing larger particle or these suspended particles may have codeposited with silica through time causing the pore spaces to be blocked by these formed solid particles. |