| Title | Modelling of Chemical and Thermal Changes in SJ4-1, San Jacinto Geothermal Field, Nicaragua |
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| Authors | R.C.M. MALATE, L.L. PRADO and J.A. GUIDOS |
| Year | 2016 |
| Conference | Stanford Geothermal Workshop |
| Keywords | injection return, chloride modeling, thermal decline, San Jacinto |
| Abstract | Production chloride changes in well SJ4-1 have been observed during it utilization since 2004. Enthalpy of the well has also declined at the start of production but remained fairly constant throughout its utilization until a small decline in enthalpy was later observed. This decline could be due to the observed thermal decline in the well coupled with wellbore pressure drawdown. A series of NDS tracer tests have been conducted to confirm the effects of injection returns to the production wells at San Jacinto. Positive tracer returns were observed in SJ4-1 from the injection fluids coming from SJ10-1. Modelling of NDS tracer recoveries in SJ4-1 gave a fraction of returning fluid at around 16%. The chloride changes are then modelled by a simple time dependent production and injection lumped parameter model using the tracer test results. Analytic solutions are employed for the cases of constant and variable production rates. The variable production rate model adequately described the chloride changes in SJ4-1. The return of injection fluids into SJ4-1 has also resulted in gradual decline in measured temperature in the well. This thermal decline is modelled by coupling the chloride mass balance model to a fracture flow model. The simple heat advection model satisfactorily represented the thermal decline observed in the well. |