| Title | Temperature Stability of Naphthalene Sulfonic and Naphthalene Disulfonic Acids at Geothermal Conditions |
|---|---|
| Authors | Yaroslav G. DASHKEVICH, Bruce W. MOUNTAIN, Terry M. SEWARD, Jeffrey A. WINICK |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | tracers, reservoir modelling, geochemistry, NDS, NDA, naphthalene, thermal stability |
| Abstract | An experiment has been performed to investigate the stability of the four naphthalene disulfonic acids (2,6-NDS, 2,7-NDS, 1,5-NDS, 1,6-NDS) and two naphthalene sulfonic acids (1-NSA, 2-NSA) using a hydrothermal flow simulator. The experimental fluid was pH-modified, low pressure separator brine from the Nga Awa Purua power station at the Rotokawa geothermal field. The six tracers were added to this fluid and were reacted with crushed, sieved and clean fragments of greywacke sourced from well RK24 at Rotokawa. The temperature range of the experiments was 270 – 390℃. Experimental results show that 1,5-NDS begins to degrade at temperatures as low as 280oC while 1,6-NDS shows evidence of breakdown at about 330oC. The other disulfonic acids are relatively stable until about 340oC at which point evidence of degradation appears. The monosulfonic acid 2-NSA is the most stable and persists to about 380oC. Analysis of the rate of reaction for these breakdown reactions shows that the rate constants are dependent on residence time and not consistent with first order reactions. The reactions that occur in the industrial production of the sulfonic acids and napthol compounds may be analogous to the reactions found at high temperatures in geothermal systems. One these reactions shows that 2-NSA is produced at higher temperature consistent with the results from the experiments. Chemical equilibria calculations show how reaction rates may be different depending on the tracer concentration and the temperature of the system. |