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Pemodelan Numerik Distribusi Temperatur Bawah Permukaan Area Manifestasi Dieng Sampai Sangubanyu, Jawa Tengah, Indonesia
INTISARI
Manifestasi Panas bumi berupa air panas-hangat Sangubanyu yang terletak di sebelah utara area panas bumi Dieng diindikasikan merupakan satu sistem panas bumi yang saling berkaitan. Sebuah model analisis numerik diusulkan untuk memahami distribusi temperatur dan tekanan dari data temperatur permukaan yang sudah diketahui menggunakan bantuan software HYDROTHERM Ver2.2. Pertama dilakukan perhitungan numerik distribusi temperatur dan tekanan keadaan tunak untuk menentukan suhu latar dan distribusi tekanan bawah permukaan. Untuk model keadaan tunak, diasumsikan tidak adanya magma di dalam sistem. Distribusi temperatur latar belakang dan pola fluks massa dihitung selama 100.000 tahun untuk mendapatkan keadaan tunak dan didapatkan keadaan tunak pada tahun ke
80.000. Langkah selanjutnya adalah memodelkan distribusi temperatur dan tekanan yang disebabkan oleh intrusi magma. Berdasarkan penelitian sebelumnya bahwa suhu reservoir tinggi dimiliki oleh manifestasi Panas Bumi Sileri, reservoir berada di kedalaman 2000 - 2300 m dengan suhu berkisar 300 – 350 oC. Berdasarkan hasil model intrusi didapatkan pola aliran fluks massa air dari reservoir berarah ke permukaan dan membentuk zona upflow Sileri ke atas dan zona outflow ke arah selatan dan utara.
Kata kunci: Distribusi temperatur, Analisis numerik, Hydrotherm2.2
ABSTRACT
Geothermal manifestation in form of hot-warm water Sangubanyu located at the north of Dieng geothermal area is indicated as an interrelated geothermal system. A numerical analysis model is proposed to understand the distribution of temperature and the pressure of surface temperature data that is already known from software support HYDROTHERM Ver2.2. First, numerical calculation of temperature distribution and steady state pressure was done to determine the background temperature and the distribution of subsurface pressure. For steady state model, we assumed that there is no magma in the system. Background temperature distribution and pattern of mass fluxes were calculated for 100,000 years to get the steady state and the steady state obtained was 80,000 years. The next step is to model the temperature and the pressure distribution caused by the magma intrusion. Based on the previous research that high-temperature reservoir owned by geothermal manifestations Sileri, the reservoir at depths betweeen 2000
- 2300 m with a temperatures range from 300-350° C. Based on the results of obtained intrusion model, the mass flux flow pattern of water from the reservoir to the surface was obtained and it forms upflow zone Sileri upward and outflow zone to the south and the north.
Keyword: Temperature distribution, Numerical analysis, Hydrotherm2.2
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