| Title | Use of TOUGHREACT to Simulate Effects of Fluid Chemistry on Injectivity in Fractured Geothermal Reservoirs with High Ionic Strength Fluids |
|---|---|
| Authors | Tianfu Xu, Guoxiang Zhang, and Karsten Pruess |
| Year | 2005 |
| Conference | Stanford Geothermal Workshop |
| Keywords | HFR, HDR, EGS, Mineral scaling, Clay swelling, Injectivity enhancing, Injectate mitigation, Reactive transport modeling. |
| Abstract | Recent studies suggest that mineral dissolution/precipitation and clay swelling effects could have a major impact on the long-term performance of hot dry rock (HDR) and hot fractured rock (HFR) reservoirs. A major concern is achieving and maintaining adequate injectivity, while avoiding the development of preferential short-circuiting flow paths. A Pitzer activity coefficient model has been introduced into the publicly available TOUGHREACT code for solving the non-isothermal multi-phase reactive geochemical transport problem under conditions of high ionic strength, expected in typical HDR and HFR systems. To explore chemically-induced effects of fluid circulation in these systems, we examine ways in which the chemical composition of reinjected waters can be modified to improve reservoir performance. Chemical manipulations considered here include pH modification and dilution with fresh water. We performed a number of coupled thermo-hydrologic-chemical simulations in which the fractured medium was represented by a one-dimensional MINC model (multiple interacting continua). Results obtained from the Pitzer activity model were compared with those from the commonly used Debye-H¸ckel model. |