Accuracy of Near Surface Geochemical Survey Development Using Soil, Water, and Soil Gas Analyses For Steam Spot Detection

The development of near-surface geochemical methods is needed to reduce the risk of unsuccess deep drilling for geothermal exploration. This study, used soil, water and soil-gas geochemistry from shallow depths monitoring holes and compared with temperature core holes (TCH) results. The methods were applied at Patuha geothermal area, West Java, Indonesia. The results of TCH drilling from 300 m depth of TCH-A and 200 m depth of TCH-B proved the accuracy of our development on the near-surface geochemical methods. Shallow monitoring holes, 2 m depth, at TTN-03 and TTN-14 were monitored for one year period before conducting the TCH-A and TCH-B drilling executed. Results of one-year periods of monitoring radon data, TTN-03, near the TCH-B, has a higher concentration of radon gas than at TTN-14. This result is strongly correlated with the results of the TCH drilling results, where TCH-B has higher geothermal gradient than the TCH-A. Clay alteration e.g., alunite and kaolinite were found from soil of TTN-03 monitoring hole. The other significant finding is TCH-B has much lower RQD values than the TCH-A, which means that the rock formation around TCH-B is more permeable and effective as geothermal fluids path-flow. The finding of study proved that our development on near surface exploration methods can be used to detect the permeable zones and the presence of steam spots in the study area.