Determine Geothermal Fluid spreading pattern under subsurface using 2d Resistivity Imaging and geomagnetic method at Silaou Kahean

Abstract

The Research has been carried out at geothermal Regional using 2d resistivity imaging and Gemagnetic method in Dusun Silou Kahean Subdistrict, Kabupaten Simalungun. The purpose of this study is to determine the distribution of earth magnetic anomalies, rock structures, and fluid distribution patterns. The measurement of geomagnetic method uses PPM (Proton Precession Magnetometer) type Elsec 770. Data retrieval have been done randomly with the number of points obtained by 40 measuring points, the data is processing by using surfer 10 to determine the contours and Mag2DC to obtain a magnetic anomaly cross section. The 2D resistivity imaging is used to determine the rock resistivity value. The results showed that the anomaly value with the geomagnetic method had the lowest value of 20.51 nT and the highest value of 67.18 nT. The susceptibility value of 0.00051 to 0,00098 cgs is indicated by sandstone and susceptibility value of 0.0013 to 0.0016 cgs is indicated by limestone. The 2D Resistivity imaging method has a resistivity value of 12.5 to 37.3 Ωm is indicated by Silts layer with a depth of 1.25-3.75 meters, and a resistivity value of 1.26 to 8.72 Ωm is indicated by c lay layer with a depth of 6.38-12.4 meters . from the results it can be concluded that the fluid dispersion contour using geomagnetic and geoelectric methods is spread across from the southwest to the northeast.