ANALISIS KOMPARATIF INDEKS SILIKA DAN KALSIT: MANUAL DENGAN PHREEQC LAPANGAN PANAS BUMI
DOI:
https://doi.org/10.53026/prosidingsntem.v5i1.682Keywords:
indeks saturasi silika, indeks saturasi kalsit, PHREEQC, scaling panas bumiAbstract
Prediksi potensi scaling panas bumi memerlukan perhitungan indeks saturasi yang akurat, namun validasi empiris metode manual versus simulasi geokimia terhadap data lapangan aktual masih terbatas. Penelitian ini memvalidasi akurasi komparatif metode Fournier-Rowe (SSI) dan stoikiometri (CSI) terhadap simulasi PHREEQC menggunakan observasi scaling aktual dari Sumur DEF-07, Lapangan XYZ, periode Mei-September 2024. Hasil menunjukkan untuk SSI, kedua metode konsisten memprediksi saturasi dengan deviasi 13,43% (manual: 0,99-1,17; PHREEQC: 1,19-1,26), keduanya sesuai dengan observasi silika scaling aktual 2-3 mm/bulan. Validasi kuantitatif menunjukkan PHREEQC lebih akurat (error 9,7%) dibanding manual (error 18,2%). Untuk CSI, terjadi kontradiksi fundamental dimana manual memprediksi supersaturated (CSI +0,007-0,008) sementara PHREEQC memprediksi undersaturated (CSI -2,19 hingga -1,61). Validasi lapangan 5 tahun mengkonfirmasi tidak ada kalsit scaling, membuktikan PHREEQC akurat sementara metode manual menghasilkan false positive 100% dengan error >200%. Root cause analysis mengidentifikasi tiga faktor: ketidakmampuan koreksi Ksp terhadap temperatur tinggi (error +1,6 log), pengabaian koefisien aktivitas pada kekuatan ionik tinggi (error +1,5 log), dan penyederhanaan spesiasi karbonat (error +1,6 log). Decision framework berbasis validasi dikembangkan: metode manual acceptable untuk monitoring SSI harian dengan error tolerance 15-20%, namun PHREEQC wajib untuk CSI. Strategi integrasi kedua metode dapat mengurangi biaya analisis 77% sambil mempertahankan akurasi prediksi.
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