Identification of the distribution of geothermal reservoirs around Kepahiang Bengkulu Province using GGMPlus gravity data anomalies by the 2D inversion method
Authors: Sihombing Patrica A , Hadi Arif Ismul , Refrizon Refrizon , Zakariya Hilmi 
Published: June 2024

Abstrak. Kabupaten Kepahiang terletak di wilayah perbatasan busur magmatik dan lempeng benua dengan lempeng samudra yang mengakibatkan munculnya beberapa manisfestasi panas bumi di permukaan berupa solfatara, fumarole, dan batuan alterasi sehingga menjadi prospek energi panas bumi. Riset yang dilakukan memiliki tujuan untuk mengetahui sebaran reservoar panas bumi di sekitar Kepahiang. Riset ini dilakukan dengan metode gravitasi, sehingga dapat dihasilkan gambaran distribusi densitas bawah permukaan. Riset ini menggunakan data Global Gravity Model Plus (GGMPlus) dengan resolusi 220 meter yaitu Free Air Anomaly (FAA) dan topografi. Berdasarkan hasil pengolahan datanya, diperoleh Anomali Bouguer Lengkap (ABL) yang merupakan gabungan anomali regional dan anomali residual. Anomali tersebut dipisahkan melalui penggunaan metode moving average. Peta anomali memberikan informasi tiga pola distribusi, yakni anomali tinggi, sedang, serta rendah. Anomali residual dimodelkan menggunakan metode inversi 2D sebanyak tujuh slice yang diduga adanya reservoar panas bumi. Hasil penelitian menunjukkan wilayah dengan nilai ABL antara 46,7 – 50,9 mGal diduga adanya reservoar panas bumi dengan nilai densitas 2,5 g/cm3 pada kedalaman yang berbeda-beda untuk setiap slice. Ketidakmunculan manisfestasi panas bumi di beberapa wilayah yang memiliki reservoar di bawah permukaan diakibatkan karena adanya batuan penudung dengan nilai densitas sebesar 2,6 - 2,7 g/cm3. Abstract. Kepahiang Regency is located in the border area of the magmatic arc and the continental plate with the oceanic plate which resulted in the emergence of several geothermal manifestations on the surface in the form of solfatara, fumarole, and alteration rocks so that it becomes a prospect for geothermal energy. The research conducted has the aim of knowing the distribution of geothermal reservoirs around Kepahiang. This research was conducted using the gravity method, so that a picture of the subsurface density distribution could be produced. This research uses Global Gravity Model Plus (GGMPlus) data with a resolution of 220 meters, namely Free Air Anomaly (FAA) and topography. Based on the results of the data processing, a Complete Bouguer Anomaly (CBA) is obtained which is a combination of regional anomalies and residual anomalies. The anomalies are separated through the use of the moving average method. The anomaly map provides information on three distribution patterns, namely high, medium and low anomalies. Residual anomalies were modeled using 2D inversion method for seven slices suspected to have geothermal reservoirs. The results show that areas with CBA values between 46.7 - 50.9 mGal are suspected to have geothermal reservoirs with density values 2.5 g/cm3 at different depths for each slice. The absence of geothermal manisfestation in some areas that have reservoirs in the subsurface is due to the presence of host rocks with a density value of 2.6 - 2.7 g/cm3.