New Insights Into the Viscosity of Polymer-Based In-Situ-Gelled Acids
| Autor: | Ahmed Mohamed Gomaa, Hisham A. Nasr-El-Din |
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| Rok vydání: | 2010 |
| Předmět: | |
| Zdroj: | SPE Production & Operations. 25:367-375 |
| ISSN: | 1930-1863 1930-1855 |
| DOI: | 10.2118/121728-pa |
| Popis: | Summary Diversion techniques must be employed to remove all the damage from the entire producing interval. Diversion in carbonates is more difficult than in sandstones because of the ability of acid to significantly increase the permeability in carbonates as the acid dissolves carbonate rocks. The apparent viscosity of the in-situ-gelled acid based on polymer plays a key role in diversion because it creates a viscosity differential in treated and untreated zones. An extensive literature survey and field data show that there is no agreement on the effectiveness of this acid system. Therefore, this study was conducted to better understand this acid system and determine factors that impact its viscosity buildup. Three commercially available in-situ acids were examined. The effect of salts and iron (III) [Fe(III)] contamination on the apparent viscosity of these acids was examined in detail. Several new findings were identified, including that polymer and other additives were separated out of the acid when these acids were prepared in high-salinity brines. Preparing the in-situ-gelled acid with saline waters decreased the viscosity of the acid in live and partially neutralized conditions. Concentrated hydrochloric acid (HCl) solutions produced high concentrations of calcium ion that reduced the viscosity of the in-situ-gelled acid system. Therefore, in-situ-gelled acids that are based on polymers should be used at low HCl concentrations (3 to 5 wt% HCl). Sodium (NaCl), calcium (CaCl2), or ferric chloride (FeCl3) reduced the apparent viscosity of live gelled acids. A brown precipitate was noted during the neutralization of acid systems that contained Fe (III), even in the presence of the recommended concentration of iron-control agents. Therefore, in-situ-gelled acids that are based on polymers should be prepared using low salinity waters and used at low HCl concentrations (3 to 5 wt% HCl). |
| Databáze: | OpenAIRE |
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