Environmental considerations in production tests and geothermal well stimulation

Abstract

The production test is one of the most important activities in geothermal development because through the production test the properties of a reservoir become known, and in this way, the amount of energy that can be extracted from it, can be evaluated. However, these tests involve certain environmental aspects that will have to be managed, such as the emission of gases and wastewater, generation of noise, etc. During well production tests in the Hengill geothermal field, environmental aspects involved in well discharges were investigated for well HE- 58, using a 35-day data period with records of water amount, steam discharge, and gas emissions to the atmosphere and the ground. For well HE-21 the amount of Fluoride (as KF) discharge into the water and the amount sulphur hexafluoride (SF6) is discharged in the steam was monitored

Another important activity is stimulation which is used when there is a decline in pressure in the well. This activity, though necessary, may have undesirable environmental effects. In this report discharge tests using lip pressure, tracer flow, and stimulation through matrix acidification, are analysed. For environmental analysis, the DASI method for identifying effects is used, and the RIAM method to evaluate the magnitude of the impacts. Finally, activities to minimize environmental effects are considered such as: using of a muffler, mitigation of H2S emissions, designing and planning a monitoring system for air and water, checking equipment and leakage, and other considerations for the minor impacts.