Eksploitasi energi panas bumi menyebabkan terjadinya perubahan parameter fisik, seperti perubahan massa di dalam reservoir akibat aktivitas produksi dan injeksi. Aktivitas produksi dan injeksi, seperti ekstraksi fluida, injeksi fluida, serta pengisian fluida secara alami dapat memengaruhi kesetimbangan massa dan aliran fluida di reservoir. Untuk menjaga keberlanjutan eksploitasi energi panas bumi, perlu dilakukan kegiatan monitoring secara berkala untuk memantau kondisi massa dan aliran fluida di reservoir. Salah satu metode yang dapat dilakukan untuk monitoring kondisi reservoir adalah Microgravity 4D. Metode Microgravity 4D dapat mendeteksi perubahan medan gravitasi berdasarkan distribusi variasi densitas batuan baik secara lateral atau horizontal di dalam reservoir. Perubahan medan gravitasi berasoisiasi dengan volume massa batuan di reservoir, yang digunakan untuk menentukan nilai perubahan massa di zona proven produksi dan injeksi. Berdasarkan hasil penelitian ini, kesetimbangan massa fluida di reservoir menunjukkan adanya massa sebesar 17,92 MTon yang diprediksi berasal dari pengisian fluida secara alami yang bergerak melewati zona struktur graben di sekitar lapangan penelitian. Pengisian fluida secara alami tersebut memberikan kontribusi pada reservoir selama periode tersebut.

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The exploitation of geothermal energy causes changes in physical parameters, such as changes in mass within the reservoir due to production and injection activities. Production and injection activities, such as fluid extraction, fluid injection, and natural fluid recharge, can affect the mass balance and fluid flow in the reservoir. To maintain the sustainability of geothermal energy exploitation, regular monitoring activities are necessary to observe the mass and fluid flow conditions in the reservoir. One method that can be used for monitoring reservoir conditions is 4D Microgravity. The 4D Microgravity method can detect changes in the gravitational field based on the distribution of rock density variations, both laterally and horizontally within the reservoir. Changes in the gravitational field are associated with the volume of rock mass in the reservoir, which is used to determine the value of mass changes in the production and injection proven zone. Based on the results of this study, the mass balance of fluid in the reservoir indicates a mass of 17.92 MTon, predicted to come from natural fluid recharge moving through the graben structure zone around the research field. This natural fluid recharge contributes to the reservoir during the period studied.